Reactions
5-exo-trig Radical Cyclization
The 5-exo-trig radical cyclization is the Baldwin's rules-allowed radical cyclization forming five-membered rings. It is kinetically favored over 6-endo-trig.
6-endo-trig Radical Cyclization
The 6-endo-trig radical cyclization forms six-membered rings but is kinetically disfavored compared to 5-exo-trig under normal conditions.
Aldol Condensation
The aldol condensation follows the aldol addition with dehydration, forming α,β-unsaturated carbonyl compounds. It is widely used for enone synthesis.
Aldol Reaction — Carbonyl Condensation
Complete guide to the aldol reaction: enolate chemistry, C-C bond formation, and α,β-unsaturated carbonyls.
Arndt–Eistert Synthesis
The Arndt–Eistert synthesis homologates carboxylic acids by one CH₂ unit via a Wolff rearrangement of a diazoketone intermediate.
Atom Transfer Radical Polymerization (ATRP)
ATRP is a controlled radical polymerization using copper catalysts with nitrogen-based ligands to give well-defined polymers with narrow molecular weight distributions.
Aza-Claisen Rearrangement
The aza-Claisen rearrangement is a [3,3]-sigmatropic rearrangement of allyl imidates to amides or of N-allyl enamines. It is useful for C–N bond formation.
Aza-Cope–Mannich Reaction
The aza-Cope–Mannich sequence combines an aza-Cope rearrangement with an intramolecular Mannich reaction, forming alkaloid skeletons in one pot.
Baeyer-Villiger Oxidation — Ketone to Ester
Complete guide to the Baeyer-Villiger oxidation: peracid oxidation of ketones to esters and lactones.
Bamberger Rearrangement
The Bamberger rearrangement converts N-phenylhydroxylamines to 4-aminophenols in acid. It involves a nitrenium ion intermediate.
Bamford–Stevens Reaction
The Bamford–Stevens reaction converts tosylhydrazones to alkenes using base in protic solvent. It gives more substituted alkenes (thermodynamic control).
Barbier Reaction
The Barbier reaction is a one-pot process where an organic halide, a carbonyl compound, and a metal react directly. It is the precursor to Grignard reactions.
Bartoli Indole Synthesis
The Bartoli indole synthesis uses ortho-substituted nitroarenes and vinyl Grignard reagents to form 7-substituted indoles in a single step.
Barton Decarboxylation
The Barton decarboxylation converts carboxylic acids to alkanes via thiohydroxamate esters (Barton esters) and radical chain reaction with Bu₃SnH.
Barton Nitrite Ester Reaction
The Barton reaction photolyzes nitrite esters to δ-nitroso alcohols, which tautomerize to oximes. It is useful for remote C–H functionalization.
Barton–McCombie Deoxygenation
The Barton–McCombie reaction removes hydroxyl groups by converting them to xanthates or thiocarbonylimidazolyl derivatives, then radical reduction with Bu₃SnH.
Barton–McCombie Deoxygenation (Detailed)
The Barton–McCombie reaction removes hydroxyl groups by radical chain mechanism. The alcohol is converted to a xanthate, then reduced with Bu₃SnH.
Batcho–Leimgruber indole synthesis
The Batcho–Leimgruber synthesis forms indoles from ortho-nitrotoluenes and DMF dimethyl acetal, followed by reduction. It gives 2-substituted indoles.
Baylis–Hillman Reaction
The Baylis–Hillman reaction couples aldehydes with electron-deficient alkenes using DABCO or other nucleophilic catalysts. It forms α-methylene-β-hydroxy compounds.
Beckmann Fragmentation
The Beckmann fragmentation is a side reaction of the Beckmann rearrangement where C–C bond cleavage occurs instead of C–N bond migration, producing nitriles and carbocations.
Beckmann Rearrangement
The Beckmann rearrangement converts oximes to amides or lactams using acid catalysts. It is industrially important for caprolactam production.
Beckwith–Houk Model
The Beckwith–Houk model predicts the stereochemistry of radical cyclizations based on transition state geometry, chair-like or boat-like arrangements.
Bellus–Claisen Rearrangement
The Bellus–Claisen rearrangement involves [3,3]-sigmatropic rearrangement of allylic ethers, thioethers, or amines with electron-deficient alkenes.
Benzidine Rearrangement
The benzidine rearrangement converts hydrazobenzenes to benzidines (4,4'-diaminobiphenyls) under acid catalysis. It is a [5,5]-sigmatropic rearrangement.
Benzilic Acid Rearrangement
The benzilic acid rearrangement converts benzil (α-diketones) to benzilic acid using strong base via a 1,2-aryl migration.
Benzilic Acid Rearrangement (Alternative)
This variant describes the broader application of the benzilic acid rearrangement to non-benzil α-diketones, forming α-hydroxy acids through 1,2-migration.
Benzyne Mechanism (Elimination-Addition)
The benzyne mechanism involves elimination of HX from an aryl halide to form a benzyne intermediate, which then adds a nucleophile. It gives mixture of regioisomers.
Birch Reduction
The Birch reduction uses alkali metals in liquid ammonia to reduce aromatic rings to 1,4-cyclohexadienes. It is useful for partially reducing aromatic compounds.
Bischler–Napieralski Reaction
The Bischler–Napieralski reaction cyclizes β-aryl ethylamides to dihydroisoquinolines using dehydrating agents. It is key for isoquinoline alkaloid synthesis.
Bohlmann–Rahtz Pyridine Synthesis
The Bohlmann–Rahtz synthesis forms 2,3,6-trisubstituted pyridines from ethynyl ketones and enamines via a Michael addition–cyclization sequence.
Bouveault–Blanc Reduction
The Bouveault–Blanc reduction reduces esters to primary alcohols using sodium metal in alcohol. It was historically important before LiAlH₄ was available.
Brown Asymmetric Allylation
The Brown asymmetric allylation uses B-allyldiisopinocampheylborane (from (+)- or (-)-α-pinene) to enantioselectively allylate aldehydes.
Brown Asymmetric Hydroboration
Brown asymmetric hydroboration uses B-methyl diisopinocampheylborane (DIP-Chloride) to enantioselectively hydroborate alkenes with high ee.
Bu₃SnH Radical Reduction
Tributyltin hydride (Bu₃SnH) is the most common reagent for radical reactions, acting as a hydrogen atom donor to terminate radical chains.
Bucherer–Bergs Reaction
The Bucherer–Bergs reaction converts carbonyl compounds to hydantoins using potassium cyanide and ammonium carbonate. Hydantoins can be hydrolyzed to α-amino acids.
Büchner Reaction
The Büchner reaction is the [6+1] cycloaddition of carbenes or diazo compounds with arenes to form cycloheptatrienes.
Büchner Reaction (Detailed)
The Büchner reaction is the [6+1] cycloaddition of carbenes with arenes to form cycloheptatrienes. Rhodium catalysts are commonly used.
Buchwald–Hartwig Amination
The Buchwald–Hartwig amination forms C–N bonds between aryl halides and amines using palladium catalysis. It is essential for pharmaceutical and materials chemistry.
Cannizzaro Reaction
The Cannizzaro reaction is the base-induced disproportionation of non-enolizable aldehydes, producing a carboxylate salt and a primary alcohol.
Catecholborane Hydroboration
Catecholborane is a more selective hydroborating agent than BH₃, giving high regioselectivity for terminal alkenes. It is useful for complex molecule synthesis.
Chan–Lam Coupling
The Chan–Lam coupling forms C–N, C–O, and C–S bonds between boronic acids and heteroatom nucleophiles under mild conditions using copper catalysis.
Chichibabin Pyridine Synthesis
The Chichibabin pyridine synthesis condenses aldehydes with ammonia or amines over solid-state catalysts at high temperature to form pyridines.
Chromium Trioxide Oxidation
CrO₃ (Jones reagent) oxidizes primary alcohols to carboxylic acids and secondary alcohols to ketones. It is powerful but toxic.
Chugaev Elimination
The Chugaev elimination converts xanthate esters to alkenes through syn-elimination upon heating. It is milder than the Hofmann elimination.
Claisen Condensation — β-Keto Ester Synthesis
Complete guide to the Claisen condensation: ester enolates, β-keto esters, and acylation reactions.
Claisen Rearrangement
The Claisen rearrangement is a [3,3]-sigmatropic rearrangement of allyl vinyl ethers to γ,δ-unsaturated carbonyl compounds. It is stereospecific and widely used in synthesis.
Clemmensen Reduction — Carbonyl to Methylene
Complete guide to the Clemmensen reduction: zinc amalgam reduction of carbonyls under acidic conditions.
Clemmensen Reduction (Detailed)
The Clemmensen reduction uses zinc amalgam and concentrated HCl to reduce ketones to methylene groups. It works best for aryl ketones.
Combes Quinoline Synthesis
The Combes quinoline synthesis condenses anilines with 1,3-diketones to form quinolines. It is a straightforward method for 2,4-disubstituted quinolines.
Conjugate Addition (1,4-Addition)
Complete guide to conjugate addition: Michael addition, cuprate addition, and 1,4 vs 1,2 selectivity.
Conrad–Limpach Synthesis
The Conrad–Limpach synthesis forms 4-hydroxyquinolines from anilines and β-ketoesters. The reaction proceeds through an imine intermediate.
Cope Elimination
The Cope elimination is a thermal syn-elimination of amine oxides to form alkenes and hydroxylamines. It proceeds through a five-membered cyclic transition state.
Cope Rearrangement
The Cope rearrangement is a [3,3]-sigmatropic rearrangement of 1,5-dienes. It is thermally reversible and often reaches equilibrium. The oxy-Cope variant is accelerated by base.
Cope Rearrangement (Detailed)
The Cope rearrangement is a [3,3]-sigmatropic rearrangement of 1,5-dienes. The reaction proceeds through a chair-like transition state and is stereospecific.
Copper-Catalyzed Azide–Alkyne Cycloaddition (CuAAC)
The CuAAC click reaction forms 1,2,3-triazoles from azides and terminal alkynes using copper(I) catalysis. It is the most widely used click reaction.
Cornforth Rearrangement
The Cornforth rearrangement converts 2-acylamino-3-oxobutanoates to 5-acetyloxazoles via acid-catalyzed cyclodehydration.
Cristol–Firth Modification
The Cristol–Firth modification of the Hunsdiecker reaction uses mercuric oxide instead of silver carboxylate for the decarboxylative bromination.
Crossed Aldol Reaction
The crossed aldol reaction uses two different carbonyl partners. Selectivity is achieved by using a preformed enolate or choosing partners with different reactivities.
Curtius Rearrangement — Acyl Azide to Isocyanate
Complete guide to the Curtius rearrangement: thermal decomposition of acyl azides to isocyanates.
Curtius Rearrangement (Detailed)
The Curtius rearrangement thermally decomposes acyl azides to isocyanates. The isocyanate can be trapped with water (→amine), alcohol (→carbamate), or amine (→urea).
Dakin Oxidation
The Dakin oxidation converts ortho- or para-hydroxybenzaldehydes to catechols or hydroquinones using hydrogen peroxide under basic conditions.
Danheiser Cyclization
The Danheiser cyclization converts allenylsilanes with electrophiles to form cyclopentenones or other five-membered rings via cationic cyclization.
De Mayo Reaction
The De Mayo reaction is the photochemical [2+2] cycloaddition of enones with alkenes, followed by retro-aldol ring opening, to form 1,5-dicarbonyl compounds.
Debus–Radziszewski Reaction
The Debus–Radziszewski reaction synthesizes imidazoles from dicarbonyl compounds, aldehydes, and ammonia. It is the classical imidazole synthesis.
Dess–Martin Periodinane Oxidation
DMP oxidizes primary and secondary alcohols to aldehydes and ketones under mild, neutral conditions. It is an alternative to Swern oxidation.
DIBAL-H Reduction
DIBAL-H (diisobutylaluminum hydride) reduces esters to aldehydes at low temperature, or reduces nitriles to aldehydes. It is a versatile reducing agent.
Dieckmann Condensation
The Dieckmann condensation is an intramolecular Claisen condensation of a diester to form a five- or six-membered cyclic β-keto ester. It is particularly useful for synthesizing cyclic compounds.
Diels-Alder Reaction — [4+2] Cycloaddition
Complete guide to the Diels-Alder reaction: pericyclic chemistry, cycloaddition, and ring formation.
Diels–Alder Click Chemistry
Diels–Alder click chemistry uses inverse electron demand Diels–Alder reactions between tetrazines and trans-cyclooctenes for ultra-fast bioconjugation.
Directed Aldol Reaction
The directed aldol uses a preformed lithium enolate for controlled addition to aldehydes, avoiding self-condensation and crossed aldol mixtures.
Doebner Modification (Knoevenagel)
The Doebner modification of the Knoevenagel reaction uses malonic acid to give α,β-unsaturated carboxylic acids directly after decarboxylation.
Doebner–Miller Synthesis
The Doebner–Miller synthesis forms quinolines from anilines and α,β-unsaturated carbonyl compounds under Brønsted or Lewis acid catalysis.
Doering–LaFlamme Cyclopropanation
The Doering–LaFlamme reaction uses diazomethane and UV light to generate carbene intermediates for cyclopropanation of alkenes.
Dötz Reaction
The Dötz reaction involves the reaction of Fischer carbene complexes with alkynes to form phenols, hydroquinones, or cyclopentenones depending on conditions.
Doyle–Kirmse Reaction
The Doyle–Kirmse reaction is a [2,3]-sigmatropic rearrangement of allylic sulfonium ylides generated from diazo compounds and allylic sulfides.
Duff Reaction
The Duff reaction formylates electron-rich aromatics using hexamethylenetetramine (HMTA) in acid. It gives ortho- and para-formylated products.
E1 Elimination — Unimolecular Elimination
Complete guide to the E1 mechanism: carbocation formation, alkene synthesis, and competition with SN1.
E2 Elimination — Bimolecular Elimination
Complete guide to the E2 mechanism: anti-periplanar geometry, Zaitsev's rule, and alkene formation.
Electrophilic Addition — Alkene Reactions
Complete guide to electrophilic addition: HX addition, halogenation, hydration, and Markovnikov's rule.
Electrophilic Aromatic Substitution (EAS)
Complete guide to EAS: nitration, halogenation, sulfonation, Friedel-Crafts, and directing effects.
Epoxidation — Three-Membered Ether Synthesis
Complete guide to epoxidation: mCPBA epoxidation, Sharpless asymmetric epoxidation, and ring-opening reactions.
Erlenmeyer–Plöchl Azlactone Synthesis
The Erlenmeyer–Plöchl reaction condenses aromatic aldehydes with hippuric acid (or N-acyl glycine) to form azlactones, which can be hydrolyzed to α-amino acids.
Eschenmoser–Claisen Rearrangement
The Eschenmoser–Claisen rearrangement uses N,N-dimethylacetamide dimethyl acetal with allyl alcohols to form γ,δ-unsaturated amides.
Favorskii Rearrangement
The Favorskii rearrangement converts α-haloketones to carboxylic acid derivatives using alkoxide or hydroxide base. It involves cyclopropanone intermediates.
Feist–Benary Furan Synthesis
The Feist–Benary synthesis condenses α-haloketones with β-dicarbonyl compounds in the presence of base to form furans.
Fischer Indole Synthesis
The Fischer indole synthesis converts aryl hydrazines with aldehydes or ketones under acid catalysis to form indoles. It is the oldest and most widely used indole synthesis.
Fischer–Hepp Rearrangement
The Fischer–Hepp rearrangement converts N-nitrosoanilines to p-nitrosoanilines under acidic conditions, with migration of the nitroso group from nitrogen to carbon.
Fleming–Tamao Oxidation
The Fleming–Tamao oxidation converts alkylsilanes to alcohols using mCPBA or H₂O₂ with fluoride. It complements the Tamao oxidation for different substrates.
Free Radical Polymerization
Free radical polymerization initiates with AIBN or peroxides and propagates through alkene addition. It is industrially important for plastic synthesis.
Friedel-Crafts Acylation — Acyl Group Introduction
Complete guide to Friedel-Crafts acylation: acyl chlorides, Lewis acid catalysis, and ketone synthesis.
Friedel-Crafts Alkylation — Electrophilic Aromatic Substitution
Complete guide to Friedel-Crafts alkylation: Lewis acid catalysis, carbocation rearrangements, and ring substitution.
Friedländer Synthesis
The Friedländer synthesis forms quinolines by condensing 2-aminobenzaldehydes with acetaldehyde or other carbonyl compounds. It is a versatile quinoline synthesis.
Gabriel Synthesis
The Gabriel synthesis produces primary amines by reacting potassium phthalimide with alkyl halides, followed by hydrazinolysis or acid hydrolysis.
Gattermann–Koch Formylation
The Gattermann–Koch reaction formylates aromatic rings using CO and HCl with AlCl₃ catalyst. It is equivalent to Friedel–Crafts with formyl chloride.
Giese Radical Addition
The Giese reaction is the radical addition of carbon-centered radicals to electron-deficient alkenes (Michael acceptors). It forms new C–C bonds under mild conditions.
Giese Reaction
The Giese reaction is the radical addition of alkyl radicals to electron-deficient alkenes (Michael acceptors). It forms new C–C bonds under mild conditions.
Goldberg Reaction
The Goldberg reaction is a copper-catalyzed N-arylation of amides with aryl halides. It is a variant of the Ullmann coupling for C–N bond formation.
Grignard Reaction — Carbon-Carbon Bond Formation
Complete guide to the Grignard reaction: organomagnesium reagents, nucleophilic addition to carbonyls, and synthesis of alcohols.
Grignard Reaction (Detailed)
The Grignard reaction forms C–C bonds by adding organomagnesium halides to carbonyl compounds. It is one of the most versatile C–C bond-forming reactions.
Grob Fragmentation
The Grob fragmentation breaks a molecule into three fragments: an electrophile, a nucleophile, and a neutral molecule (usually an amine or ether). It requires antiperiplanar geometry.
Groebke–Blackburn–Bienaymé Reaction
The GBB reaction is a three-component condensation of aldehydes, isocyanides, and 2-aminopyridines to form imidazo[1,2-a]pyridines. It is useful for drug discovery.
Grubbs Olefin Metathesis
Grubbs metathesis uses ruthenium carbene catalysts to exchange alkylidene groups between alkenes. It has revolutionized organic synthesis and won the 2005 Nobel Prize.
Guareschi–Thorpe Pyridine Synthesis
The Guareschi–Thorpe synthesis condenses cyanoacetamide with 1,3-dicarbonyl compounds to form 2-pyridones, which can be converted to pyridines.
Hajos–Parrish Reaction
The Hajos–Parrish reaction is a proline-catalyzed asymmetric aldol cyclization that forms bicyclic ketones with excellent enantioselectivity. It is a landmark in organocatalysis.
Hantzsch Pyridine Synthesis
The Hantzsch pyridine synthesis forms 1,4-dihydropyridines from two equivalents of a β-ketoester, an aldehyde, and ammonia. Oxidation gives pyridines.
Hantzsch Pyrrole Synthesis
The Hantzsch pyrrole synthesis forms pyrroles from β-ketoesters, α-haloketones, and ammonia or amines. It is a versatile three-component synthesis.
Hartwig–Buchwig Amination (Aryl Chlorides)
The Hartwig–Bucton amination of aryl chlorides uses specialized catalysts to activate the less reactive C–Cl bond for C–N bond formation.
Heck Reaction — Palladium-Catalyzed Olefination
Complete guide to the Heck reaction: Pd-catalyzed coupling of aryl halides with alkenes.
Heck Reaction (Detailed)
The Heck reaction couples aryl or vinyl halides with alkenes using palladium catalysis. It forms substituted alkenes with high regioselectivity.
Hell–Volhard–Zelinsky Reaction
The HVZ reaction brominates carboxylic acids at the α-position using bromine and phosphorus tribromide. It is useful for α-functionalization of acids.
Henry (Nitroaldol) Reaction
The Henry reaction couples nitroalkanes with aldehydes or ketones to form β-nitro alcohols. It is a powerful C–C bond-forming reaction.
Hiyama Coupling
The Hiyama coupling uses organosilicon compounds with a palladium catalyst to form C–C bonds. It is less toxic than Stille coupling and uses environmentally friendly reagents.
Hofmann Elimination
The Hofmann elimination converts amines to alkenes through exhaustive methylation and quaternary ammonium hydroxide formation, followed by E2 elimination.
Hofmann Rearrangement — Amide to Amine
Complete guide to the Hofmann rearrangement: conversion of primary amides to amines with one fewer carbon.
Hofmann Rearrangement (Detailed)
The Hofmann rearrangement converts primary amides to amines with one fewer carbon using bromine and base. The mechanism involves a nitrene intermediate or concerted migration.
Hofmann–Löffler–Freytag Reaction
The HLF reaction is a radical process that converts N-haloamines to pyrrolidines via δ-hydrogen abstraction. It is a precursor to Barton–McCombie chemistry.
Horner–Wadsworth–Emmons Reaction
The HWE reaction is a modification of the Wittig reaction using phosphonate esters instead of phosphonium ylides. It gives E-alkenes preferentially and uses water-soluble byproducts.
Hunsdiecker Reaction
The Hunsdiecker reaction converts silver carboxylates to alkyl bromides using bromine, losing CO₂. It is a decarboxylative halogenation.
Hydroboration–Oxidation
Hydroboration–oxidation converts alkenes to alcohols with anti-Markovnikov regioselectivity and syn stereoselectivity. It is one of the most useful alkene reactions.
Hydroboration–Oxidation (Detailed)
Hydroboration–oxidation converts alkenes to alcohols with anti-Markovnikov regioselectivity and syn stereoselectivity. BH₃ adds to the less substituted carbon.
Ireland–Claisen Rearrangement
The Ireland–Claisen rearrangement converts allyl esters to γ,δ-unsaturated acids via silyl ketene acetals. It is stereoselective and widely used in natural product synthesis.
Jacobsen–Katsuki Epoxidation
The Jacobsen–Katsuki epoxidation uses chiral manganese-salen complexes to enantioselectively epoxidize unfunctionalized alkenes.
Johnson–Claisen Rearrangement
The Johnson–Claisen rearrangement converts allyl alcohols with trialkyl orthoacetates to γ,δ-unsaturated esters under acid catalysis.
Jones Oxidation
The Jones oxidation uses chromium trioxide in dilute sulfuric acid to oxidize primary alcohols to carboxylic acids and secondary alcohols to ketones.
Julia Olefination
The Julia olefination (or Julia–Lythgoe olefination) converts aldehydes or ketones into alkenes using a sulfone. The modified Julia reaction uses a one-pot procedure.
Keck Allylation
The Keck asymmetric allylation uses chiral lanthanide catalysts with allylstannanes to enantioselectively form homoallylic alcohols.
Keck Radical Allylation
The Keck radical allylation uses allylstannanes with AIBN to couple radicals with aldehydes or other radical acceptors.
Kharasch Addition (Anti-Markovnikov)
The Kharasch addition is the free-radical addition of HBr to alkenes with anti-Markovnikov regioselectivity, initiated by peroxides or light.
Kharasch–Sosnovsky Reaction
The Kharasch–Sosnovsky reaction allylically oxidizes alkenes to allylic esters or alcohols using copper catalysts and peroxides.
Knoevenagel Condensation
The Knoevenagel condensation couples aldehydes or ketones with active methylene compounds (e.g., malonates, cyanoacetates) using weak base catalysts.
Knoevenagel Condensation (Detailed)
The Knoevenagel condensation reacts aldehydes or ketones with active methylene compounds using amine bases. The Doebner modification gives α,β-unsaturated acids.
Knorr Furan Synthesis
The Knorr furan synthesis dehydrates acyloin (α-hydroxyketone) derivatives using acid to form furans.
Knorr Pyrrole Synthesis
The Knorr pyrrole synthesis couples an α-amino ketone with a β-ketoester or 1,3-dicarbonyl to form highly substituted pyrroles.
Knorr Quinoline Synthesis
The Knorr quinoline synthesis uses aniline with a β-ketoester to form 4-hydroxy-2-methylquinoline. It is related to the Conrad–Limpach synthesis.
Kolbe Electrolysis
The Kolbe electrolysis couples carboxylate radicals at the anode to form alkanes. It is an electrochemical method for C–C bond formation.
Kröhnke Pyridine Synthesis
The Kröhnke pyridine synthesis uses pyridinium salts and α,β-unsaturated carbonyls to form highly substituted pyridines under mild conditions.
Kulinkovich Reaction
The Kulinkovich reaction converts esters with Grignard reagents (EtMgBr) and Ti(OⁱPr)₄ to form cyclopropanols. It involves titanacyclopropane intermediates.
Kumada Coupling
The Kumada coupling is the earliest Pd- or Ni-catalyzed cross-coupling reaction, forming C–C bonds between Grignard reagents and organic halides.
Larock Indole Synthesis
The Larock indole synthesis forms indoles from ortho-iodoanilines and internal alkynes via palladium-catalyzed heteroannulation.
Lindlar Reduction
The Lindlar reduction selectively reduces alkynes to cis-alkenes using Lindlar catalyst (Pd/CaCO₃ poisoned with Pb or quinoline). It is a syn-hydrogenation.
Lithium Aluminium Hydride Reduction
LiAlH₄ reduces esters, carboxylic acids, aldehydes, ketones, amides, and nitriles to alcohols or amines. It is a powerful but non-selective reducing agent.
Lossen Rearrangement
The Lossen rearrangement converts hydroxamic acids to isocyanates under dehydrating conditions, similar to the Hofmann and Curtius rearrangements.
Luche Reduction
The Luche reduction selectively reduces α,β-unsaturated ketones to allylic alcohols using NaBH₄ and cerium trichloride, avoiding 1,4-reduction.
Manganese Dioxide Oxidation
MnO₂ selectively oxidizes allylic and benzylic alcohols to the corresponding aldehydes or ketones. It is mild and chemoselective.
Mannich Reaction
The Mannich reaction is a three-component condensation of an amine, a carbonyl compound, and a compound with an active hydrogen. It forms β-amino carbonyl compounds.
Marckwald Imidazole Synthesis
The Marckwald imidazole synthesis forms 2-aminoimidazoles from α-aminoketones and cyanamide or potassium cyanate.
Markovnikov Addition
Markovnikov's rule states that in the addition of HX to alkenes, the hydrogen adds to the less substituted carbon. This is the standard electrophilic addition pathway.
McFadyen–Stevens Reaction
The McFadyen–Stevens reaction converts arenecarboxylic acids to aldehydes via sulfonylhydrazides, providing a mild method for aromatic aldehyde synthesis.
Meerwein–Ponndorf–Verley Reduction
The MPV reduction reduces ketones to secondary alcohols using aluminum isopropoxide. It is reversible and selective for C=O reduction.
Meisenheimer Rearrangement
The Meisenheimer rearrangement is a [1,2]-rearrangement of amine oxides to N,N-disubstituted hydroxylamines under thermal conditions.
Meyer–Schuster Rearrangement
The Meyer–Schuster rearrangement converts propargylic alcohols to α,β-unsaturated carbonyl compounds under acid catalysis.
Michael Addition — Conjugate Addition to α,β-Unsaturated Systems
Complete guide to the Michael addition: conjugate addition of nucleophiles to enones and related systems.
Minisci Radical Alkylation
The Minisci reaction is the radical alkylation of protonated nitrogen heterocycles using peroxides and carboxylic acids. It is complementary to electrophilic substitution.
Minisci Reaction
The Minisci reaction is the radical alkylation of protonated nitrogen heterocycles (pyridines, quinolines) using peroxides and carboxylic acids.
Morita–Baylis–Hillman Reaction
The MBH reaction is the nucleophilic-catalyzed coupling of activated alkenes with aldehydes, producing allylic alcohols with a new C–C bond.
Mozingo Desulfurization (Raney Ni)
The Mozingo reduction uses Raney nickel to desulfurize thioacetals, converting C=O to CH₂. It is useful for acid-sensitive substrates.
Mozingo Reduction (Raney Ni Desulfurization)
The Mozingo reduction uses Raney nickel to desulfurize thioacetals, converting C=O to CH₂. It is useful for acid-sensitive substrates where Clemmensen fails.
Mukaiyama Aldol Reaction
The Mukaiyama aldol reaction uses silyl enol ethers with aldehydes under Lewis acid catalysis. It avoids self-condensation and gives controlled aldol products.
Nametkin Rearrangement
The Nametkin rearrangement involves methyl migration in camphene hydrochloride and related terpene systems during solvolysis reactions.
Nazarov Cyclization
The Nazarov cyclization converts divinyl ketones to cyclopentenones using Lewis acids or Brønsted acids. It is a [4+1] electrocyclic reaction.
Neber Rearrangement
The Neber rearrangement converts oxime sulfonates to α-aminoketones, which can then cyclize to oxazoles or other heterocycles.
Negishi Coupling — Organozinc Cross-Coupling
Complete guide to the Negishi coupling: Pd-catalyzed reaction of organozinc compounds with organic halides.
Negishi Coupling (Alkyl Electrophiles)
The Negishi coupling with alkyl electrophiles requires specialized catalysts to prevent β-hydride elimination, enabling C(sp3)–C bond formation.
Nicholas Reaction
The Nicholas reaction uses cobalt-stabilized propargylic cations for C–C bond formation. The cationic intermediate can be trapped with nucleophiles.
Norrish Type I Reaction
The Norrish Type I reaction is the α-cleavage of carbonyl compounds upon photolysis, producing radicals that can undergo decarbonylation or recombination.
Norrish Type II Reaction
The Norrish Type II reaction is the intramolecular hydrogen abstraction of carbonyl compounds with γ-hydrogens upon photolysis, producing an enol and an alkene.
Nozaki–Hiyama–Kishi Reaction
The NHK reaction couples vinyl halides with aldehydes using chromium(II) chloride. It is mild and chemoselective, tolerating many functional groups.
Nucleophilic Addition — Carbonyl Reactions
Complete guide to nucleophilic addition: Grignard, hydride, cyanide, and Wittig reactions to carbonyls.
Nucleophilic Aromatic Substitution (SNAr)
SNAr replaces a leaving group on an electron-deficient aromatic ring with a nucleophile. It proceeds through a Meisenheimer complex intermediate.
Oppenauer Oxidation
The Oppenauer oxidation is the reverse of the MPV reduction, oxidizing secondary alcohols to ketones using aluminum tert-butoxide and acetone.
Organolithium Addition
Organolithium reagents (RLi) are more reactive than Grignard reagents and can add to less electrophilic carbonyls. They are stronger bases and nucleophiles.
Oxy-Cope Rearrangement
The oxy-Cope rearrangement is a Cope rearrangement of 1,5-dien-3-ols, which is dramatically accelerated by deprotonation (anionic oxy-Cope) to give enolates.
Oxy-Cope Rearrangement (Detailed)
The oxy-Cope rearrangement of 3-hydroxy-1,5-dienes is dramatically accelerated by deprotonation (anionic oxy-Cope). The product enol tautomerizes to give an aldehyde or ketone.
Oxymercuration–Demercuration
Oxymercuration–demercuration converts alkenes to Markovnikov alcohols without carbocation rearrangements. It proceeds through a mercurinium ion intermediate.
Paal–Knorr Furan Synthesis
The Paal–Knorr furan synthesis dehydrates 1,4-dicarbonyl compounds using acid catalysts to form furans.
Paal–Knorr Pyrrole Synthesis
The Paal–Knorr pyrrole synthesis converts 1,4-dicarbonyl compounds to pyrroles using ammonia or amines. It is the most straightforward pyrrole synthesis.
Paal–Knorr Synthesis
The Paal–Knorr synthesis forms furans, pyrroles, or thiophenes from 1,4-dicarbonyl compounds. The heteroatom source (NH₃, Na₂S, acid) determines the product.
Passerini Three-Component Reaction
The Passerini reaction condenses a carboxylic acid, an aldehyde, and an isocyanide to form α-acyloxy amides. It is an isocyanide-based multicomponent reaction.
Paterno–Büchi Reaction
The Paterno–Büchi reaction is the [2+2] photocycloaddition of carbonyl compounds with alkenes to form oxetanes.
Pauson–Khand Reaction
The Pauson–Khand reaction is a [2+2+1] cycloaddition of an alkyne, an alkene, and CO catalyzed by cobalt carbonyl. It forms cyclopentenones.
PCC Oxidation
PCC (pyridinium chlorochromate) oxidizes primary alcohols to aldehydes without overoxidation to carboxylic acids. It is a milder alternative to Jones oxidation.
PDC Oxidation
PDC (pyridinium dichromate) is a milder oxidant than PCC. It oxidizes primary alcohols to aldehydes and secondary alcohols to ketones in DMF or CH₂Cl₂.
Perkin Condensation
The Perkin condensation reacts aromatic aldehydes with acetic anhydride using sodium acetate to form cinnamic acids. It is a classic aldol-type condensation.
Perkin Reaction
The Perkin reaction condenses aromatic aldehydes with acid anhydrides using the corresponding sodium carboxylate base. It forms α,β-unsaturated aromatic acids.
Petasis Reaction (Borono–Mannich)
The Petasis reaction combines boronic acids, amines, and carbonyl compounds to form α-substituted amines. It is a versatile three-component Mannich-type reaction.
Peterson Olefination
The Peterson olefination converts carbonyl compounds to alkenes using α-silyl carbanions. The stereochemistry of the product depends on the reaction conditions (acid or base workup).
Pictet–Spengler Reaction
The Pictet–Spengler reaction forms tetrahydroisoquinolines and β-carbolines by condensing β-arylethylamines with aldehydes under acid catalysis.
Pinacol Rearrangement
The Pinacol rearrangement converts 1,2-diols (pinacols) to ketones or aldehydes using acid catalysis. It involves a carbocation intermediate and 1,2-migration.
Polonovski Reaction
The Polonovski reaction converts tertiary amine oxides to N-alkylated iminium ions using acetic anhydride, which can be trapped with nucleophiles.
Pomeranz–Fritsch Reaction
The Pomeranz–Fritsch reaction synthesizes isoquinolines from benzaldehyde and aminoacetaldehyde dimethyl acetal under acidic conditions.
Radical Addition to Alkenes
Radical additions to alkenes form new C–C bonds and are widely used in synthesis. The Giese reaction and related processes are key examples.
Ramberg–Bäcklund Reaction
The Ramberg–Bäcklund reaction converts α-halo sulfones to alkenes with loss of SO₂. It forms C=C bonds through an episulfone intermediate.
Rauhut–Currier Reaction
The Rauhut–Currier reaction is a phosphine-catalyzed dimerization of electron-deficient alkenes to form 1,4-dienes. It is related to the Baylis–Hillman reaction.
Red-Al Reduction
Red-Al (sodium bis(2-methoxyethoxy)aluminium hydride) is a safer alternative to LiAlH₄ with similar reducing power but better solubility in organic solvents.
Reformatsky Reaction
The Reformatsky reaction couples α-halo esters with aldehydes or ketones using zinc metal to form β-hydroxy esters. It is related to the aldol reaction.
Reimer–Tiemann Reaction
The Reimer–Tiemann reaction hydroxylates phenols using chloroform and base. It introduces a formyl group ortho to the hydroxyl group.
Retro-Diels–Alder Reaction
The retro-Diels–Alder reaction is the reverse of the Diels–Alder reaction, breaking a cyclohexene into a diene and a dienophile. It is used in synthesis and polymer chemistry.
Reversible Addition-Fragmentation Chain Transfer (RAFT)
RAFT is a controlled radical polymerization using chain transfer agents (dithioesters, trithiocarbonates) to control molecular weight and dispersity.
Riley Oxidation
The Riley oxidation uses selenium dioxide to oxidize allylic or benzylic positions to allylic alcohols or carbonyl compounds.
Ring-Opening Metathesis Polymerization (ROMP)
ROMP polymerizes cyclic alkenes using Grubbs or Schrock catalysts. It produces polymers with controlled molecular weights and narrow dispersities.
Robinson Annulation
The Robinson annulation is a key method for constructing six-membered rings. It combines a Michael addition with an intramolecular aldol condensation, forming bicyclic systems.
Robinson–Gabriel Synthesis
The Robinson–Gabriel synthesis dehydrates 2-acylaminoketones to form oxazoles using sulfuric acid or phosphorus pentoxide.
Rosenmund Reduction
The Rosenmund reduction selectively reduces acyl chlorides to aldehydes using palladium on barium sulfate poisoned with quinoline-sulfur (Lindlar-type catalyst).
Roush Crotylation
The Roush crotylation uses tartrate-crotylboronate esters to synthesize anti or syn homoallylic alcohols with high diastereo- and enantioselectivity.
Rubottom Oxidation
The Rubottom oxidation converts silyl enol ethers to α-hydroxy carbonyl compounds using mCPBA, followed by hydrolysis.
Rupe Rearrangement
The Rupe rearrangement is an acid-catalyzed conversion of tertiary propargylic alcohols to α,β-unsaturated ketones. It competes with the Meyer–Schuster rearrangement.
Sakurai–Hosomi–Yamamoto Reaction
The Sakurai reaction is the Lewis acid-mediated allylation of aldehydes or ketones with allylsilanes. It is a mild alternative to Barbier-type reactions.
Saucy–Marbet Reaction
The Saucy–Marbet reaction is the base-catalyzed rearrangement of propargylic alcohols to α,β-unsaturated carbonyl compounds (allenols then tautomerize).
Schmidt Reaction
The Schmidt reaction of ketones with hydrazoic acid produces amides or lactams. It is related to the Beckmann rearrangement but uses HN₃.
Schmidt Reaction of Ketones
The Schmidt reaction of ketones with hydrazoic acid gives amides or lactams. It is acid-catalyzed and involves alkyl migration to nitrogen.
Selenium Dioxide Oxidation
SeO₂ oxidizes allylic and benzylic positions to allylic alcohols or carbonyls. It proceeds through an ene reaction followed by [2,3]-sigmatropic rearrangement.
Shapiro Reaction
The Shapiro reaction converts tosylhydrazones to alkenes using two equivalents of strong base. It gives less substituted alkenes (opposite of Bamford–Stevens).
Sharpless Asymmetric Epoxidation (Detailed)
The Sharpless asymmetric epoxidation enantioselectively epoxidizes allylic alcohols using titanium(IV) isopropoxide, diethyl tartrate, and tert-butyl hydroperoxide.
Sharpless Dihydroxylation
The Sharpless asymmetric dihydroxylation converts alkenes to chiral 1,2-diols using osmium tetroxide with chiral ligands (AD-mix). It won the 2001 Nobel Prize.
Sharpless Epoxidation
The Sharpless epoxidation enantioselectively epoxidizes allylic alcohols using titanium isopropoxide, diethyl tartrate, and TBHP. It won the 2001 Nobel Prize.
Simmons–Smith Cyclopropanation
The Simmons–Smith reaction converts alkenes to cyclopropanes using a zinc-copper carbenoid (ICH₂ZnI). It is a concerted syn-addition.
Simonini Reaction
The Simonini reaction is the electrolysis of silver carboxylates to form esters, a variant of the Kolbe electrolysis.
Skraup Synthesis
The Skraup synthesis forms quinolines from aniline and glycerol in the presence of sulfuric acid and an oxidizing agent. It is one of the oldest quinoline syntheses.
Smiles Rearrangement
The Smiles rearrangement is an intramolecular nucleophilic aromatic substitution where a group migrates from one aromatic ring to another via a spiro intermediate.
SN1 Reaction — Unimolecular Nucleophilic Substitution
Complete guide to the SN1 mechanism: carbocation intermediates, racemization, and solvent effects.
SN2 Reaction — Bimolecular Nucleophilic Substitution
Complete guide to the SN2 mechanism: backside attack, Walden inversion, and stereochemistry.
Sodium Borohydride Reduction
NaBH₄ selectively reduces aldehydes and ketones to alcohols, leaving esters, carboxylic acids, and amides unaffected. It is safer and easier to handle than LiAlH₄.
Sommelet–Hauser Rearrangement
The Sommelet–Hauser rearrangement is a [2,3]-sigmatropic rearrangement of ammonium ylides, producing ortho-substituted benzylamines.
Sonogashira Coupling — Alkyne-Aryl Bond Formation
Complete guide to the Sonogashira coupling: Pd/Cu-catalyzed reaction of terminal alkynes with aryl halides.
Sonogashira Coupling (Detailed)
The Sonogashira coupling forms C(sp2)–C(sp) bonds between aryl/vinyl halides and terminal alkynes using Pd and Cu co-catalysts.
Stephen Aldehyde Synthesis
The Stephen synthesis converts nitriles to aldehydes using stannous chloride and HCl, proceeding through an imidoyl chloride intermediate.
Stevens Rearrangement
The Stevens rearrangement is a [1,2]-rearrangement of ammonium or sulfonium ylides. It converts ammonium salts to amines with migration of a group from nitrogen to carbon.
Stille Coupling
The Stille coupling uses organotin compounds to form C–C bonds with organic halides via palladium catalysis. It tolerates many functional groups but involves toxic tin reagents.
Strain-Promoted Azide–Alkyne Cycloaddition (SPAAC)
SPAAC is a copper-free click reaction where strained cyclooctynes react with azides to form triazoles. It is used in biological systems where copper is toxic.
Strecker Synthesis
The Strecker synthesis is one of the oldest methods for synthesizing α-amino acids. It condenses aldehydes with ammonia and hydrogen cyanide to form α-aminonitriles.
Suárez Reaction
The Suárez reaction converts 1,3-diols to epoxides using iodobenzene diacetate and iodine under photolytic or thermal conditions.
Suzuki Coupling — Palladium-Catalyzed Cross-Coupling
Complete guide to Suzuki coupling: Pd-catalyzed C-C bond formation with organoboron reagents.
Suzuki–Miyaura Coupling (Detailed)
The Suzuki coupling forms C–C bonds between aryl/vinyl halides and boronic acids using palladium catalysis. It is widely used in pharmaceutical synthesis.
Suzuki–Miyaura Variation (Aryl Chlorides)
The Suzuki–Miyaura coupling of aryl chlorides requires specialized palladium catalysts with bulky phosphine ligands to activate the less reactive C–Cl bond.
Swern Oxidation
The Swern oxidation oxidizes primary and secondary alcohols to aldehydes and ketones using DMSO and oxalyl chloride. It is widely used in synthesis.
Tamao Oxidation
The Tamao oxidation converts organosilicon compounds to alcohols using peroxides and fluoride, allowing silicon to serve as a hydroxyl surrogate.
TEMPO Oxidation
TEMPO (2,2,6,6-tetramethylpiperidin-1-oxyl) is a stable radical that catalytically oxidizes primary alcohols to aldehydes using bleach as terminal oxidant.
Thiol–Ene Click Reaction
The thiol–ene reaction adds thiols to alkenes under radical or base catalysis. It is a highly efficient click reaction for materials and bioconjugation.
Tiemann Rearrangement
The Tiemann rearrangement converts imidates to amides under basic conditions via a [1,3]-shift of the alkoxy group from oxygen to nitrogen.
Tiffeneau–Demjanov Rearrangement
The Tiffeneau–Demjanov rearrangement ring-expands cyclic β-amino alcohols using nitrous acid, forming ring-expanded ketones.
Tin-Free Radical Chemistry
Tin-free radical methods use tris(trimethylsilyl)silane (TTMSS) or other silanes instead of Bu₃SnH to avoid toxic tin byproducts.
Tishchenko Reaction
The Tishchenko reaction converts aldehydes to esters using aluminum alkoxide catalysts. It is a disproportionation with alkoxide transfer.
Truce–Smiles Rearrangement
The Truce–Smiles rearrangement is a carbanion version of the Smiles rearrangement, where a carbanion migrates intramolecularly to an electrophilic aromatic ring.
Ugi Four-Component Reaction
The Ugi reaction is a four-component condensation of an amine, aldehyde, carboxylic acid, and isocyanide to form α-acylamino amides. It is widely used in combinatorial chemistry.
Ullmann Coupling
The Ullmann coupling is a copper-catalyzed C–C bond formation between aryl halides. It is one of the oldest named reactions and remains useful for biaryl synthesis.
van Leusen Imidazole Synthesis
The van Leusen imidazole synthesis uses TosMIC with imines to form imidazoles. It is a versatile method for 1,4- and 1,5-disubstituted imidazoles.
van Leusen Oxazole Synthesis
The van Leusen oxazole synthesis uses TosMIC with aldehydes or ketones to form oxazolines or oxazoles, providing a versatile route to oxazole heterocycles.
van Leusen Pyrrole Synthesis
The van Leusen pyrrole synthesis uses tosylmethyl isocyanide (TosMIC) with electron-deficient alkenes or carbonyl compounds to form pyrroles.
Vilsmeier–Haack Formylation
The Vilsmeier–Haack reaction formylates electron-rich aromatics using DMF and POCl₃. The active species is a chloroiminium ion.
von Braun Amide Degradation
The von Braun amide degradation converts secondary amides to cyanamides using cyanogen bromide, providing a method for amide bond cleavage.
von Braun Reaction
The von Braun reaction converts tertiary amines to cyanamides and alkyl bromides using cyanogen bromide. It is a method for amine degradation.
Von Richter Reaction
The Von Richter reaction converts aromatic nitro compounds to carboxylic acids using cyanide and reducing agent. It proceeds through a benzyne-like intermediate.
Wagner–Meerwein Rearrangement
The Wagner–Meerwein rearrangement is a 1,2-alkyl or aryl shift in carbocation intermediates. It occurs in terpene biosynthesis and organic synthesis.
Willgerodt–Kindler Reaction
The Willgerodt–Kindler reaction converts aryl alkyl ketones to amides using sulfur and morpholine. The carbonyl group migrates to the terminal position.
Williamson Ether Synthesis — Ether Formation
Complete guide to the Williamson ether synthesis: alkoxide nucleophiles, SN2 reactions, and ether preparation.
Wittig Reaction — Alkene Synthesis from Carbonyls
Complete guide to the Wittig reaction: phosphonium ylides, stereoselectivity, and alkene synthesis.
Wittig Rearrangement
The Wittig rearrangement is a [1,2]- or [2,3]-sigmatropic rearrangement of ethers to alcohols. The [2,3]-version is stereoselective and synthetically more useful.
Wolff Rearrangement
The Wolff rearrangement converts α-diazoketones to ketenes using heat, light, or metal catalysts. The ketene can be trapped to form carboxylic acids or amides.
Wolff-Kishner Reduction — Hydrazone Decomposition
Complete guide to the Wolff-Kishner reduction: hydrazine reduction of carbonyls under basic conditions.
Wolff–Kishner Reduction (Detailed)
The Wolff–Kishner reduction converts ketones to methylene groups using hydrazine and base. The Huang–Minlon modification uses diethylene glycol as solvent.
Yang Cyclization
The Yang cyclization is the intramolecular cyclization of 1,4-biradicals formed in the Norrish Type II reaction, producing cyclobutanol derivatives.