Alkyne trimerisation

Chemical reaction of three alkynes to form a benzene ring

An alkyne trimerisation is a [2+2+2] cycloaddition reaction in which three alkyne units (C≡C) react to form a benzene ring. The reaction requires a metal catalyst. The process is of historic interest as well as being applicable to organic synthesis.[1] Being a cycloaddition reaction, it has high atom economy. Many variations have been developed, including cyclisation of mixtures of alkynes and alkenes as well as alkynes and nitriles.

## Mechanism and stereochemistry

[edit]

Trimerisation of acetylene to benzene is highly exergonic, proceeding with a free energy change of 142 kcal/mol at room temperature. Kinetic barriers however prevent the reaction from proceeding smoothly. The breakthrough came in 1948, when Walter Reppe and W. J. Schweckendiek reported their wartime results showing that nickel compounds are effective catalysts:[2][3]

3 RC2H → C6R3H3

Since this discovery, many other cyclotrimerisations have been reported.[4]

### Mechanism

[edit]

In terms of mechanism, the reactions begin with the formation of metal-alkyne complexes. The combination of two alkynes within the coordination sphere affords a metallacyclopentadiene.[5] Starting from the metallacyclopentadiene intermediate, many pathways can be considered including metallocycloheptatrienes, metallanorbornadienes, and a more complicated structure featuring a carbenoid ligand.[4]

Simplified mechanism for metal-catalyzed trimerisation of alkynes

Catalysts used include cyclopentadienylcobalt dicarbonyl and Wilkinson's catalyst.

### Stereochemistry and regiochemistry

[edit]

Trimerisation of unsymmetrical alkynes gives two isomeric benzenes. For example, phenylacetylene affords both 1,3,5- and 1,2,4-C6R3H3. The substitution pattern about the product arene is determined in two steps: formation of the metallocyclopentadiene intermediate and incorporation of the third equivalent of alkyne. Steric bulk on the alkyne coupling partners and catalyst have been invoked as the controlling elements of regioselectivity.

Three proposed intermediates in alkyne trimerization.[4]

Chiral catalysts have been employed in combination with arynes to produce non-racemic atropisomeric products.[6]

### Scope and limitations

[edit]

Catalysts for cyclotrimerisation are selective for triple bonds, which gives the reaction a fairly wide substrate scope. Many functional groups are tolerated. Regioselective intermolecular trimerization of unsymmetrical alkynes remains an unsolved problem.[4]

Perhaps the most useful development in this area, at least from the commercial perspective is the cotrimerization of nitriles and alkynes. This reaction is a practical route to some substituted pyridines.[7]

Some catalysts are deactivated by formation of stable, 18-electron η4-complexes. Cyclobutadiene, cyclohexadiene, and arene complexes have all been observed as off-cycle, inactivated catalysts.[8] In addition to high-order polymers and dimers and trimers, which originate from low regio- and chemoselectivities, enyne side products derived from alkyne dimerisation have been observed. Rhodium catalysts are particularly adept at enyne formation (see below).[9] For nickel catalysis, formation of larger rings (particularly cyclooctatetraene) can be a problem.

## Synthetic applications

[edit]

Alkyne trimerization is of no practical value, although the reaction was highly influential. The cotrimerization of alkynes and nitriles in the presence of organocobalt catalysts has been commercialized for the production of substituted pyridines.[10]

Cyclization involving substrates in which some or all of the alkyne units are tethered together can provide fused ring systems. The length of the tether(s) controls the sizes of the additional rings. Addition of a 1,5-diyne with an alkyne produces a benzocyclobutene, a strained structure that can then be induced to undergo further reactions.[11]

All three alkyne units can be tethered, leading to creation of three rings in a single step, with each of the two additional ring sizes controlled by the respective tether lengths.[12]

Crowded triynes can cyclize to products exhibiting helical chirality. In one example remarkable for the formation of three new aromatic rings in one step, the triyne shown is transformed into the helical product via treatment with cyclopentadienylcobalt dicarbonyl.[13] As of 2004, this process had yet to be rendered asymmetric,[original research?] but the products could be separated through chiral HPLC.[13] Cyclisation carried out with a diyne and a separate alkyne affords greater control.[clarification needed] Using commercially available cyclopentadienylcobalt dicarbonyl, CpCo(CO)2, as catalyst, bis(trimethylsilyl)acetylene (BTMSA) will react with a diyne-1,2-disubstituted benzene to form an anthroquinone aromatic system:[14]

Benzyne, generated in situ from a benzene ring bearing ortho-distributed triflate and trimethylsilyl substituents, can be used to generate an aryne in place of an acetylene and combined with a suitable diyne. Such a benzene derivative reacts with 1,7-octadiyne in the presence of a suitable catalyst to generate a naphthalene system.[15] This is an example of a hexadehydro Diels–Alder reaction.

Trimerisation of three 2-butyne (dimethylacetylene) molecules yields hexamethylbenzene.[16] The reaction is catalyzed by triphenylchromium tri-tetrahydrofuranate[17] or by a complex of triisobutylaluminium and titanium tetrachloride.[18]

Trimerisation of three diphenylacetylene molecules yields hexaphenylbenzene. The reaction is catalyzed by dicobalt octacarbonyl.[19]

## Comparison with other methods

[edit]

Cyclotrimerization presents an alternative to the functionalization of pre-formed aromatic compounds through electrophilic or nucleophilic substitution, the regioselectivity of which can sometimes be difficult to control.

Other methods for the direct formation of aromatic rings from substituted, unsaturated precursors include the Dötz reaction, palladium-catalyzed [4+2] benzannulation of enynes with alkynes,[20] and Lewis-acid-mediated [4+2] cycloaddition of enynes with alkynes.[21] Cyclization of transient benzyne species with alkynes, catalyzed by palladium, can also produce substituted aromatic compounds.[22]

## Further reading

[edit]

* Musso, F.; Solari, E.; Floriani, C. (1997). "Hydrocarbon Activation with Metal Halides: Zirconium Tetrachloride Catalyzing the Jacobsen Reaction and Assisting the Trimerization of Alkynes via the Formation of η6-Arene−Zirconium(IV) Complexes". Organometallics. 16 (22): 4889. doi:10.1021/om970438g.
* Rodríguez, J. Gonzalo; Martín-Villamil, Rosa; Fonseca, Isabel (1997). "Tris(2,4-pentanedionato)vanadium-catalysed cyclotrimerization and polymerization of 4-(N,N-dimethylamino)phenylethyne: X-ray structure of 1,2,4-tris[4-(N,N -dimethylamino)phenyl]benzene". Journal of the Chemical Society, Perkin Transactions 1 (6): 945–948\. doi:10.1039/a605474i. ISSN 0300-922X.
* Sakurai, H.; Nakadaira, Y.; Hosomi, A.; Eriyama, Y.; Hirama, K.; Kabuto, C. (1984). "Chemistry of organosilicon compounds. 193. Intramolecular cyclotrimerization of macrocylic and acyclic triynes with Group 6 metal carbonyls. The formation of fulvene and benzene". J. Am. Chem. Soc. 106 (26): 8315. doi:10.1021/ja00338a063.
* Amer, I.; Bernstein, T.; Eisen, M.; Blum, J.; Vollhardt, K. P. C. (1990). "Oligomerization of alkynes by the RhCl3-aliquat 336 catalyst system Part 1. Formation of benzene derivatives". J. Mol. Catal. 60 (3): 313. doi:10.1016/0304-5102(90)85254-F.
* Lee, C. L.; Hunt, C. T.; Balch, A. L. (1981). "Novel reactions of metal-metal bonds. Reactions of Pd2{(C6H5)2PCH2P(C6H5)2}2Cl2 with acetylenes, olefins, and isothiocyanates". Inorg. Chem. 20 (8): 2498. doi:10.1021/ic50222a026.
* Aalten, H. L.; van Koten, G.; Riethorst, E.; Stam, C. H. (1989). "The Hurtley reaction. 2. Novel complexes of disubstituted acetylenes with copper(I) benzoates having a reactive ortho carbon-chlorine or carbon-bromine bond. X-ray structural characterization of tetrakis(2-chlorobenzoato)bis(diethyl acetylenedicarboxylate)tetracopper(I)". Inorg. Chem. 28 (22): 4140. doi:10.1021/ic00321a020.
* Hardesty, J. H.; Koerner, J. B.; Albright, T. A.; Lee, G. B. (1999). "Theoretical Study of the Acetylene Trimerization with CpCo". J. Am. Chem. Soc. 121 (25): 6055. Bibcode:1999JAChS.121.6055H. doi:10.1021/ja983098e.
* Ozerov, O. V.; Patrick, B. O.; Ladipo, F. T. (2000). "Highly Regioselective [2 + 2 + 2] Cycloaddition of Terminal Alkynes Catalyzed by η6-Arene Complexes of Titanium Supported by Dimethylsilyl-Bridgedp-tert-Butyl Calix[4]arene Ligand". J. Am. Chem. Soc. 122 (27): 6423. doi:10.1021/ja994543o.

## References

[edit]

1. ^ Agenet, N.; Buisine, O.; Slowinski, F.; Gandon, V.; Aubert, C.; Malacria, M. (2007). "Cotrimerizations of Acetylenic Compounds". Org. React. 68: 1–302\. doi:10.1002/0471264180.or068.01. ISBN 978-0471264187.
2. ^ Reppe, W.; Schweckendiek, W. J. (1948). "Cyclisierende Polymerisation von Acetylen. III Benzol, Benzolderivate und hydroaromatische Verbindungen". Liebigs Ann. Chem. 560: 104–116\. doi:10.1002/jlac.19485600104.
3. ^ Reppe, W.; Vetter, H. (1953). "Carbonylierung VI. Synthesen mit Metallcarbonylwasserstoffen". Liebigs Ann. Chem. 585: 133–161\. doi:10.1002/jlac.19535820107.
4. ^ a b c d Broere, Daniel L. J.; Ruijter, Eelco (2012). "Recent advances in transition-metal-catalyzed [2 + 2 + 2]-cyclo(co)trimerization reactions". Synthesis. 44 (17): 2639–2672\. doi:10.1055/s-0032-1316757.
5. ^ Ma, Wangyang; Yu, Chao; Chen, Tianyang; Xu, Ling; Zhang, Wen-Xiong; Xi, Zhenfeng (2017). "Metallacyclopentadienes: synthesis, structure and reactivity". Chemical Society Reviews. 46 (4): 1160–1192\. doi:10.1039/C6CS00525J. ISSN 0306-0012. PMID 28119972.
6. ^ Shibata, Takanori; Tsuchikama, Kyoji (2008). "Recent advances in enantioselective [2 + 2 + 2] cycloaddition". Organic & Biomolecular Chemistry. 6 (8): 1317–1323\. doi:10.1039/b720031e. ISSN 1477-0520. PMID 18385836.
7. ^ Varela, Jesus; Saa, Carlos (March 20, 2003). "Construction of Pyridine Rings by Metal-Mediated [2 + 2 + 2] Cycloaddition". Chemical Reviews. 103 (9): 3787–3802\. doi:10.1021/cr030677f. PMID 12964884.
8. ^ Kölle, U.; Fuss, B. (1986). "Pentamethylcyclopentadienyl-Übergangsmetall-Komplexe, X. Neue Co-Komplexe aus η5-C5Me5Co-Fragmenten und Acetylenen". Chem. Ber. 119: 116–128\. doi:10.1002/cber.19861190112.
9. ^ Ardizzoia, G. A.; Brenna, S.; Cenini, S.; LaMonica, G.; Masciocchi, N.; Maspero, A. (2003). "Oligomerization and Polymerization of Alkynes Catalyzed by Rhodium(I) Pyrazolate Complexes". J. Mol. Catal. A: Chemical. 204–205: 333–340\. doi:10.1016/S1381-1169(03)00315-7.
10. ^ Shimizu, S.; Watanabe, N.; Kataoka, T.; Shoji, T.; Abe, N.; Morishita, S.; Ichimura, H. "Pyridine and Pyridine Derivatives". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a22_399. ISBN 978-3-527-30673-2.
11. ^ Vollhardt, K. Peter C. (1984). "Cobalt-assisted [2+2+2] cycloadditions: a synthesis strategy grows to maturity". Angewandte Chemie. 96 (8): 525–41\. doi:10.1002/ange.19840960804.
12. ^ Neeson, S. J.; Stevenson, P. J. (1988). "Rhodium catalysed [2+2+2] cycloadditions- an efficient regiospecific route to calomelanolactone". Tetrahedron Lett. 29 (7): 813. doi:10.1016/S0040-4039(00)80217-8.
13. ^ a b Teply, F.; Stara, I. G.; Stary, I.; Kollarovic, A.; Saman, D.; Rulisek, L.; Fiedler, P. (2002). "Synthesis of 5-, 6-, and 7helicene via Ni(0)- or Co(I)-catalyzed isomerization of aromatic cis,cis-dienetriynes". J. Am. Chem. Soc. 124 (31): 9175–80\. Bibcode:2002JAChS.124.9175T. doi:10.1021/ja0259584. PMID 12149022.
14. ^ Hillard, R. L.; Vollhardt, K. P. C. (1977). "Substituted Benzocyclobutenes, Indans, and Tetralins via Cobalt-Catalyzed Cooligomerization of α,ω-diynes with Substituted Acetylenes. Formation and Synthetic Utility of Trimethylsilylated Benzocycloalkenes". Journal of the American Chemical Society. 99 (12): 4058–4069\. doi:10.1021/ja00454a026.
15. ^ Hsieh, J.-C.; Cheng, C.-H. (2005). "Nickel-Catalyzed Cocyclotrimerization of Arynes with Diynes; A Novel Method for Synthesis of Naphthalene Derivatives". Chemical Communications. 2005 (19): 2459–2461\. doi:10.1039/b415691a. PMID 15886770.
16. ^ Weber, S. R.; Brintzinger, H. H. (1977). "Reactions of Bis(hexamethylbenzene)iron(0) with Carbon Monoxide and with Unsaturated Hydrocarbons". J. Organomet. Chem. 127 (1): 45–54\. doi:10.1016/S0022-328X(00)84196-0. hdl:2027.42/22975.
17. ^ Zeiss, H. H.; Herwig, W. (1958). "Acetylenic π-complexes of chromium in organic synthesis". J. Am. Chem. Soc. 80 (11): 2913. Bibcode:1958JAChS..80.2913Z. doi:10.1021/ja01544a091.
18. ^ Franzus, B.; Canterino, P. J.; Wickliffe, R. A. (1959). "Titanium tetrachloride–trialkylaluminum complex—A cyclizing catalyst for acetylenic compounds". J. Am. Chem. Soc. 81 (6): 1514. doi:10.1021/ja01515a061.
19. ^ Vij, V.; Bhalla, V.; Kumar, M. (8 August 2016). "Hexaarylbenzene: Evolution of Properties and Applications of Multitalented Scaffold". Chemical Reviews. 116 (16): 9565–9627\. doi:10.1021/acs.chemrev.6b00144. PMID 27498592.
20. ^ Gevorgyan, V.; Takeda, A.; Homma, M.; Sadayori, N.; Radhakrishnan, U.; Yamamoto, Y. (1999). "Palladium-Catalyzed [4+2]Cross-Benzannulation Reaction of Conjugated Enynes with Diynes and Triynes". J. Am. Chem. Soc. 121 (27): 6391. doi:10.1021/ja990749d.
21. ^ Wills, M. S. B.; Danheiser, R. L. (1998). "Intramolecular [4 + 2] Cycloaddition Reactions of Conjugated Ynones. Formation of Polycyclic Furans via the Generation and Rearrangement of Strained Heterocyclic Allenes". J. Am. Chem. Soc. 120 (36): 9378. doi:10.1021/ja9819209.
22. ^ Sato, Y.; Tamura, T.; Mori, M. (2004). "Arylnaphthalene lignans through Pd-Catalyzed 2+2+2 cocyclization of arynes and diynes: total synthesis of Taiwanins C and E". Angew. Chem. Int. Ed. Engl. 43 (18): 2436–40\. doi:10.1002/anie.200453809. PMID 15114584.

* v
* t
* e

Alkynes

* Ethyne (C2H2)
* Propyne (C3H4)
* Butyne (C4H6)
* 1
* 2
* Pentyne (C5H8)
* 1
* 2
* Hexyne (C6H10)
* 1
* 2
* 3
* Heptyne (C7H12)
* Octyne (C8H14)
* 2
* 4
* Nonyne (C9H16)
* Decyne (C10H18)
* 1
* 5

Preparations|

* Cracking
* Dehydrogenation of alkane, alkene
* Alkylation of alkynyl anion
* Dehydrohalogenation of dihaloalkane
* Fritsch–Buttenberg–Wiechell rearrangement
* Corey–Fuchs reaction
* Seyferth–Gilbert homologation

Reactions|

* Deprotonation
* Hydrogenation
* Halogenation
* Hydration
* Hydroboration
* Hydrohalogenation
* Alkynylation
* Thiol-yne reaction
* Alkyne trimerisation
* Diels–Alder reaction
* Pauson–Khand reaction
* Azide-alkyne Huisgen cycloaddition
* Sonogashira coupling
* Cadiot–Chodkiewicz coupling
* Glaser coupling
* Favorskii reaction

* v
* t
* e

Topics in organic reactions

* Addition reaction
* Elimination reaction
* Polymerization
* Reagents
* Rearrangement reaction
* Redox reaction
* Regioselectivity
* Stereoselectivity
* Stereospecificity
* Substitution reaction

* A value
* Alpha effect
* Annulene
* Anomeric effect
* Antiaromaticity
* Aromatic ring current
* Aromaticity
* Baird's rule
* Baker–Nathan effect
* Baldwin's rules
* Bema Hapothle
* Beta-silicon effect
* Bicycloaromaticity
* Bredt's rule
* Bürgi–Dunitz angle
* Catalytic resonance theory
* Charge remote fragmentation
* Charge-transfer complex
* Clar's rule
* Conformational isomerism
* Conjugated system
* Conrotatory and disrotatory
* Curtin–Hammett principle
* Dynamic binding (chemistry)
* Edwards equation
* Effective molarity
* Electromeric effect
* Electron-rich
* Electron-withdrawing group
* Electronic effect
* Electrophile
* Evelyn effect
* Flippin–Lodge angle
* Free-energy relationship
* Grunwald–Winstein equation
* Hammett acidity function
* Hammett equation
* George S. Hammond
* Hammond's postulate
* Homoaromaticity
* Hückel's rule
* Hyperconjugation
* Inductive effect
* Kinetic isotope effect
* LFER solvent coefficients (data page)
* Marcus theory
* Markovnikov's rule
* Möbius aromaticity
* Möbius–Hückel concept
* More O'Ferrall–Jencks plot
* Negative hyperconjugation
* Neighbouring group participation
* 2-Norbornyl cation
* Nucleophile
* Kennedy J. P. Orton
* Passive binding
* Phosphaethynolate
* Polar effect
* Polyfluorene
* Ring strain
* Σ-aromaticity
* Spherical aromaticity
* Spiroaromaticity
* Steric effects
* Superaromaticity
* Swain–Lupton equation
* Taft equation
* Thorpe–Ingold effect
* Vinylogy
* Walsh diagram
* Woodward–Hoffmann rules
* Woodward's rules
* Y-aromaticity
* Yukawa–Tsuno equation
* Zaitsev's rule
* Σ-bishomoaromaticity

List of organic reactions

Carbon-carbon
bond forming
reactions|

* Acetoacetic ester synthesis
* Acyloin condensation
* Aldol condensation
* Aldol reaction
* Alkane metathesis
* Alkyne metathesis
* Alkyne trimerisation
* Alkynylation
* Allan–Robinson reaction
* Arndt–Eistert reaction
* Auwers synthesis
* Aza-Baylis–Hillman reaction
* Barbier reaction
* Barton–Kellogg reaction
* Baylis–Hillman reaction
* Benary reaction
* Bergman cyclization
* Biginelli reaction
* Bingel reaction
* Blaise ketone synthesis
* Blaise reaction
* Blanc chloromethylation
* Bodroux–Chichibabin aldehyde synthesis
* Bouveault aldehyde synthesis
* Bucherer–Bergs reaction
* Buchner ring expansion
* Cadiot–Chodkiewicz coupling
* Carbonyl allylation
* Carbonyl olefin metathesis
* Castro–Stephens coupling
* Chan rearrangement
* Chan–Lam coupling
* Claisen condensation
* Claisen rearrangement
* Claisen-Schmidt condensation
* Combes quinoline synthesis
* Corey–Fuchs reaction
* Corey–House synthesis
* Coupling reaction
* Cross-coupling reaction
* Cross dehydrogenative coupling
* Cross-coupling partner
* Dakin–West reaction
* Darzens reaction
* Diels–Alder reaction
* Doebner reaction
* Wulff–Dötz reaction
* Ene reaction
* Enyne metathesis
* Ethenolysis
* Favorskii reaction
* Ferrier carbocyclization
* Friedel–Crafts reaction
* Fujimoto–Belleau reaction
* Fujiwara–Moritani reaction
* Fukuyama coupling
* Gabriel–Colman rearrangement
* Gattermann reaction
* Glaser coupling
* Grignard reaction
* Grignard reagent
* Hammick reaction
* Heck reaction
* Henry reaction
* Heterogeneous metal catalyzed cross-coupling
* High dilution principle
* Hiyama coupling
* Homologation reaction
* Horner–Wadsworth–Emmons reaction
* Hydrocyanation
* Hydrovinylation
* Hydroxymethylation
* Ivanov reaction
* Johnson–Corey–Chaykovsky reaction
* Julia olefination
* Julia–Kocienski olefination
* Kauffmann olefination
* Knoevenagel condensation
* Knorr pyrrole synthesis
* Kolbe–Schmitt reaction
* Kowalski ester homologation
* Kulinkovich reaction
* Kumada coupling
* Liebeskind–Srogl coupling
* Malonic ester synthesis
* Mannich reaction
* McMurry reaction
* Meerwein arylation
* Methylenation
* Michael reaction
* Minisci reaction
* Mizoroki-Heck vs. Reductive Heck
* Nef isocyanide reaction
* Nef synthesis
* Negishi coupling
* Nierenstein reaction
* Nitro-Mannich reaction
* Nozaki–Hiyama–Kishi reaction
* Olefin conversion technology
* Olefin metathesis
* Palladium–NHC complex
* Passerini reaction
* Peterson olefination
* Pfitzinger reaction
* Piancatelli rearrangement
* Pinacol coupling reaction
* Prins reaction
* Quelet reaction
* Ramberg–Bäcklund reaction
* Rauhut–Currier reaction
* Reformatsky reaction
* Reimer–Tiemann reaction
* Rieche formylation
* Ring-closing metathesis
* Robinson annulation
* Sakurai reaction
* Seyferth–Gilbert homologation
* Shapiro reaction
* Sonogashira coupling
* Stetter reaction
* Stille reaction
* Stollé synthesis
* Stork enamine alkylation
* Suzuki reaction
* Takai olefination
* Thermal rearrangement of aromatic hydrocarbons
* Thorpe reaction
* Ugi reaction
* Ullmann reaction
* Wagner-Jauregg reaction
* Weinreb ketone synthesis
* Wittig reaction
* Wurtz reaction
* Wurtz–Fittig reaction
* Zincke–Suhl reaction

| Homologation reactions|

* Arndt–Eistert reaction
* Hooker reaction
* Kiliani–Fischer synthesis
* Kowalski ester homologation
* Methoxymethylenetriphenylphosphorane
* Seyferth–Gilbert homologation
* Wittig reaction

|

Olefination reactions|

* Bamford–Stevens reaction
* Barton–Kellogg reaction
* Boord olefin synthesis
* Chugaev elimination
* Cope reaction
* Corey–Winter olefin synthesis
* Dehydrohalogenation
* Elimination reaction
* Grieco elimination
* Hofmann elimination
* Horner–Wadsworth–Emmons reaction
* Hydrazone iodination
* Julia olefination
* Julia–Kocienski olefination
* Kauffmann olefination
* McMurry reaction
* Peterson olefination
* Ramberg–Bäcklund reaction
* Shapiro reaction
* Takai olefination
* Wittig reaction

Carbon-heteroatom
bond forming
reactions|

* Azo coupling
* Bartoli indole synthesis
* Boudouard reaction
* Cadogan–Sundberg indole synthesis
* Diazonium compound
* Esterification
* Grignard reagent
* Haloform reaction
* Hegedus indole synthesis
* Hurd–Mori 1,2,3-thiadiazole synthesis
* Kharasch–Sosnovsky reaction
* Knorr pyrrole synthesis
* Leimgruber–Batcho indole synthesis
* Mukaiyama hydration
* Nenitzescu indole synthesis
* Oxymercuration reaction
* Reed reaction
* Schotten–Baumann reaction
* Ullmann condensation
* Williamson ether synthesis
* Yamaguchi esterification

Degradation
reactions|

* Barbier–Wieland degradation
* Bergmann degradation
* Edman degradation
* Emde degradation
* Gallagher–Hollander degradation
* Hofmann rearrangement
* Hooker reaction
* Isosaccharinic acid
* Marker degradation
* Ruff degradation
* Strecker degradation
* Von Braun amide degradation
* Weerman degradation
* Wohl degradation

Organic redox
reactions|

* Acyloin condensation
* Adkins–Peterson reaction
* Akabori amino-acid reaction
* Alcohol oxidation
* Algar–Flynn–Oyamada reaction
* Amide reduction
* Andrussow process
* Angeli–Rimini reaction
* Aromatization
* Autoxidation
* Baeyer–Villiger oxidation
* Barton–McCombie deoxygenation
* Bechamp reduction
* Benkeser reaction
* Bergmann degradation
* Birch reduction
* Bohn–Schmidt reaction
* Bosch reaction
* Bouveault–Blanc reduction
* Boyland–Sims oxidation
* Cannizzaro reaction
* Carbonyl reduction
* Clemmensen reduction
* Collins oxidation
* Corey–Itsuno reduction
* Corey–Kim oxidation
* Corey–Winter olefin synthesis
* Criegee oxidation
* Dakin oxidation
* Davis oxidation
* Deoxygenation
* Dess–Martin oxidation
* DNA oxidation
* Elbs persulfate oxidation
* Emde degradation
* Eschweiler–Clarke reaction
* Étard reaction
* Fischer–Tropsch process
* Fleming–Tamao oxidation
* Fukuyama reduction
* Ganem oxidation
* Glycol cleavage
* Griesbaum coozonolysis
* Grundmann aldehyde synthesis
* Haloform reaction
* Hydrogenation
* Hydrogenolysis
* Hydroxylation
* Jones oxidation
* Kiliani–Fischer synthesis
* Kolbe electrolysis
* Kornblum oxidation
* Kornblum–DeLaMare rearrangement
* Leuckart reaction
* Ley oxidation
* Lindgren oxidation
* Lipid peroxidation
* Lombardo methylenation
* Luche reduction
* Markó–Lam deoxygenation
* McFadyen–Stevens reaction
* Meerwein–Ponndorf–Verley reduction
* Methionine sulfoxide
* Miyaura borylation
* Mozingo reduction
* Noyori asymmetric hydrogenation
* Omega oxidation
* Oppenauer oxidation
* Oxygen rebound mechanism
* Ozonolysis
* Parikh–Doering oxidation
* Pinnick oxidation
* Prévost reaction
* Reduction of nitro compounds
* Reductive amination
* Riley oxidation
* Rosenmund reduction
* Rubottom oxidation
* Sabatier reaction
* Sarett oxidation
* Selenoxide elimination
* Shapiro reaction
* Sharpless asymmetric dihydroxylation
* Epoxidation of allylic alcohols
* Sharpless epoxidation
* Sharpless oxyamination
* Stahl oxidation
* Staudinger reaction
* Stephen aldehyde synthesis
* Swern oxidation
* Transfer hydrogenation
* Wacker process
* Wharton reaction
* Whiting reaction
* Wohl–Aue reaction
* Wolff–Kishner reduction
* Wolffenstein–Böters reaction
* Zinin reaction

Rearrangement
reactions|

* 1,2-rearrangement
* 1,2-Wittig rearrangement
* 2,3-sigmatropic rearrangement
* 2,3-Wittig rearrangement
* Achmatowicz reaction
* Alkyne zipper reaction
* Allen–Millar–Trippett rearrangement
* Allylic rearrangement
* Alpha-ketol rearrangement
* Amadori rearrangement
* Arndt–Eistert reaction
* Aza-Cope rearrangement
* Baker–Venkataraman rearrangement
* Bamberger rearrangement
* Banert cascade
* Beckmann rearrangement
* Benzilic acid rearrangement
* Bergman cyclization
* Bergmann degradation
* Boekelheide reaction
* Brook rearrangement
* Buchner ring expansion
* Carroll rearrangement
* Chan rearrangement
* Claisen rearrangement
* Cope rearrangement
* Corey–Fuchs reaction
* Cornforth rearrangement
* Criegee rearrangement
* Curtius rearrangement
* Demjanov rearrangement
* Di-π-methane rearrangement
* Dimroth rearrangement
* Divinylcyclopropane-cycloheptadiene rearrangement
* Dowd–Beckwith ring-expansion reaction
* Electrocyclic reaction
* Ene reaction
* Enyne metathesis
* Favorskii reaction
* Favorskii rearrangement
* Ferrier carbocyclization
* Ferrier rearrangement
* Fischer–Hepp rearrangement
* Fries rearrangement
* Fritsch–Buttenberg–Wiechell rearrangement
* Gabriel–Colman rearrangement
* Group transfer reaction
* Halogen dance rearrangement
* Hayashi rearrangement
* Hofmann rearrangement
* Hofmann–Martius rearrangement
* Ireland–Claisen rearrangement
* Jacobsen rearrangement
* Kornblum–DeLaMare rearrangement
* Kowalski ester homologation
* Lobry de Bruyn–Van Ekenstein transformation
* Lossen rearrangement
* McFadyen–Stevens reaction
* McLafferty rearrangement
* Meyer–Schuster rearrangement
* Mislow–Evans rearrangement
* Mumm rearrangement
* Myers allene synthesis
* Nazarov cyclization reaction
* Neber rearrangement
* Newman–Kwart rearrangement
* Overman rearrangement
* Oxy-Cope rearrangement
* Pericyclic reaction
* Piancatelli rearrangement
* Pinacol rearrangement
* Pummerer rearrangement
* Ramberg–Bäcklund reaction
* Ring expansion and contraction
* Ring-closing metathesis
* Rupe reaction
* Schmidt reaction
* Semipinacol rearrangement
* Seyferth–Gilbert homologation
* Sigmatropic reaction
* Skattebøl rearrangement
* Smiles rearrangement
* Sommelet–Hauser rearrangement
* Stevens rearrangement
* Stieglitz rearrangement
* Thermal rearrangement of aromatic hydrocarbons
* Tiffeneau–Demjanov rearrangement
* Vinylcyclopropane rearrangement
* Wagner–Meerwein rearrangement
* Wallach rearrangement
* Weerman degradation
* Westphalen–Lettré rearrangement
* Willgerodt rearrangement
* Wolff rearrangement

Ring forming
reactions|

* 1,3-Dipolar cycloaddition
* Annulation
* Azide-alkyne Huisgen cycloaddition
* Baeyer–Emmerling indole synthesis
* Bartoli indole synthesis
* Bergman cyclization
* Biginelli reaction
* Bischler–Möhlau indole synthesis
* Bischler–Napieralski reaction
* Blum–Ittah aziridine synthesis
* Bobbitt reaction
* Bohlmann–Rahtz pyridine synthesis
* Borsche–Drechsel cyclization
* Bucherer carbazole synthesis
* Bucherer–Bergs reaction
* Cadogan–Sundberg indole synthesis
* Camps quinoline synthesis
* Chichibabin pyridine synthesis
* Cook–Heilbron thiazole synthesis
* Cycloaddition
* Darzens reaction
* Davis–Beirut reaction
* De Kimpe aziridine synthesis
* Debus–Radziszewski imidazole synthesis
* Dieckmann condensation
* Diels–Alder reaction
* Feist–Benary synthesis
* Ferrario–Ackermann reaction
* Fiesselmann thiophene synthesis
* Fischer indole synthesis
* Fischer oxazole synthesis
* Friedländer synthesis
* Gewald reaction
* Graham reaction
* Hantzsch pyridine synthesis
* Hegedus indole synthesis
* Hemetsberger indole synthesis
* Hofmann–Löffler reaction
* Hurd–Mori 1,2,3-thiadiazole synthesis
* Iodolactonization
* Isay reaction
* Jacobsen epoxidation
* Johnson–Corey–Chaykovsky reaction
* Knorr pyrrole synthesis
* Knorr quinoline synthesis
* Kröhnke pyridine synthesis
* Kulinkovich reaction
* Larock indole synthesis
* Madelung synthesis
* Nazarov cyclization reaction
* Nenitzescu indole synthesis
* Niementowski quinazoline synthesis
* Niementowski quinoline synthesis
* Paal–Knorr synthesis
* Paternò–Büchi reaction
* Pechmann condensation
* Petrenko-Kritschenko piperidone synthesis
* Pictet–Spengler reaction
* Pomeranz–Fritsch reaction
* Prilezhaev reaction
* Pschorr cyclization
* Reissert indole synthesis
* Ring-closing metathesis
* Robinson annulation
* Sharpless epoxidation
* Simmons–Smith reaction
* Skraup reaction
* Urech hydantoin synthesis
* Van Leusen reaction
* Wenker synthesis

| Cycloaddition|

* 1,3-Dipolar cycloaddition
* 4+4 Photocycloaddition
* (4+3) cycloaddition
* 6+4 Cycloaddition
* Alkyne trimerisation
* Aza-Diels–Alder reaction
* Azide-alkyne Huisgen cycloaddition
* Bradsher cycloaddition
* Cheletropic reaction
* Conia-ene reaction
* Cyclopropanation
* Diazoalkane 1,3-dipolar cycloaddition
* Diels–Alder reaction
* Enone–alkene cycloadditions
* Hexadehydro Diels–Alder reaction
* Intramolecular Diels–Alder cycloaddition
* Inverse electron-demand Diels–Alder reaction
* Ketene cycloaddition
* McCormack reaction
* Metal-centered cycloaddition reactions
* Nitrone-olefin (3+2) cycloaddition
* Oxo-Diels–Alder reaction
* Ozonolysis
* Pauson–Khand reaction
* Povarov reaction
* Prato reaction
* Retro-Diels–Alder reaction
* Staudinger synthesis
* Trimethylenemethane cycloaddition
* Vinylcyclopropane (5+2) cycloaddition
* Wagner-Jauregg reaction

|

Heterocycle forming reactions|

* Algar–Flynn–Oyamada reaction
* Allan–Robinson reaction
* Auwers synthesis
* Bamberger triazine synthesis
* Banert cascade
* Barton–Zard reaction
* Bernthsen acridine synthesis
* Bischler–Napieralski reaction
* Bobbitt reaction
* Boger pyridine synthesis
* Borsche–Drechsel cyclization
* Bucherer carbazole synthesis
* Bucherer–Bergs reaction
* Chichibabin pyridine synthesis
* Cook–Heilbron thiazole synthesis
* Diazoalkane 1,3-dipolar cycloaddition
* Einhorn–Brunner reaction
* Erlenmeyer–Plöchl azlactone and amino-acid synthesis
* Feist–Benary synthesis
* Fischer oxazole synthesis
* Gabriel–Colman rearrangement
* Gewald reaction
* Hantzsch ester
* Hantzsch pyridine synthesis
* Herz reaction
* Knorr pyrrole synthesis
* Kröhnke pyridine synthesis
* Lectka enantioselective beta-lactam synthesis
* Lehmstedt–Tanasescu reaction
* Niementowski quinazoline synthesis
* Nitrone-olefin (3+2) cycloaddition
* Paal–Knorr synthesis
* Pellizzari reaction
* Pictet–Spengler reaction
* Pomeranz–Fritsch reaction
* Prilezhaev reaction
* Robinson–Gabriel synthesis
* Stollé synthesis
* Urech hydantoin synthesis
* Wenker synthesis
* Wohl–Aue reaction

*[v]: View this template
*[t]: Discuss this template
*[e]: Edit this template