Barton–Kellogg reaction
Barton–Kellogg reaction | |
---|---|
Named after | Sir Derek Barton Richard M. Kellogg |
Reaction type | Coupling reaction |
Identifiers | |
RSC ontology ID | RXNO:0000495 |
The Barton–Kellogg reaction is a coupling reaction between a diazo compound and a thioketone, giving an alkene by way of an episulfide intermediate.[1][2][3] The Barton–Kellogg reaction is also known as Barton–Kellogg olefination[4] and Barton olefin synthesis.[5]
![The Barton-Kellogg reaction](/uploads/wikipedia/commons/thumb/3/32/Barton-Kellogg_reaction.svg/350px-Barton-Kellogg_reaction.svg.png?auto=webp)
This reaction was pioneered by Hermann Staudinger,[6] and also goes by the name Staudinger type diazo-thioketone coupling.
Reaction mechanism
[edit]In the reaction mechanism for this reaction, the diazo compound reacts as a 1,3-dipole in a 1,3-dipolar cycloaddition with the thioketone to give a 5-membered thiadiazoline ring. This intermediate is unstable; it extrudes a molecule of nitrogen to form a thiocarbonyl ylide, which then cyclizes to form a stable episulfide. Triphenylphosphine reacts as a nucleophile, opening the three-membered ring to form a sulfaphosphatane. In a manner similar to the Wittig reaction, this structure then expels triphenylphosphine sulfide to produce an alkene.
![Barton-Kellogg reaction mechanism](/uploads/wikipedia/commons/thumb/f/fd/Barton%E2%80%93Kellogg_reaction_mechanism.svg/450px-Barton%E2%80%93Kellogg_reaction_mechanism.svg.png?auto=webp)
Scope
[edit]The diazo compound can be obtained from a ketone by reaction with hydrazine to a hydrazone followed by oxidation. Many reagents exist for this conversion for example silver(I) oxide and (bis(trifluoroacetoxy)iodo)benzene.[7] The thioketone required for this reaction can be obtained from a ketone and phosphorus pentasulfide. Desulfurization of the episulfide can be accomplished by many phosphines and also by copper powder.
![Barton-Kellogg reaction molecular motor synthesis](/uploads/wikipedia/commons/thumb/2/2b/Barton-Kellogg_reaction_example.svg/550px-Barton-Kellogg_reaction_example.svg.png?auto=webp)
The main advantage of this reaction over the McMurry reaction is the notion that the reaction can take place with two different ketones. In this regard the diazo-thioketone coupling is a cross-coupling rather than a homocoupling.
References
[edit]- ^ D. H. R. Barton & B. J. Willis (1970). "Olefin synthesis by twofold extrusion processes". J. Chem. Soc. D (19): 1225. doi:10.1039/C29700001225.
- ^ R. M. Kellogg & S. Wassenaar (1970). "Thiocarbonyl ylides. An approach to "tetravalent sulfur" compounds". Tetrahedron Lett. 11 (23): 1987. doi:10.1016/S0040-4039(01)98134-1.
- ^ R. M. Kellogg (1976). "The molecules R2CXCR2 including azomethine, carbonyl and thiocarbonyl ylides. Their syntheses, properties and reactions". Tetrahedron. 32 (18): 2165–2184. doi:10.1016/0040-4020(76)85131-9.
- ^ "Barton-Kellogg olefination". Comprehensive Organic Name Reactions and Reagents. 2010. pp. 249–253. doi:10.1002/9780470638859.conrr056. ISBN 9780470638859.
- ^ "Barton olefin synthesis". Merck Index (15th ed.).
- ^ H. Staudinger & J. Siegwart (1920). "Einwirkungen von aliphatischen Diazoverbindungen auf Thioketone". Helv. Chim. Acta. 3: 833–840. doi:10.1002/hlca.19200030178.
- ^ Matthijs K. J. ter Wiel; Javier Vicario; Stephen G. Davey; Auke Meetsma & Ben L. Feringa (2005). "New procedure for the preparation of highly sterically hindered alkenes using a hypervalent iodine reagent" (PDF). Organic & Biomolecular Chemistry. 3 (1): 28–30. doi:10.1039/b414959a. PMID 15602594.