Eschenmoser fragmentation
From Wikipedia, the free encyclopedia
The Eschenmoser fragmentation (also called the Eschenmoser-Tanabe fragmentation) is the chemical reaction of α,β-epoxyketones (1) with aryl sulfonylhydrazines (2) to give alkynes (3) and carbonyl compounds (4).
Several examples exist in the literature.
[edit] Reaction mechanism
The mechanism of the Eschenmoser fragmentation begins with reaction of the α,β-epoxyketone (1) with aryl sulfonylhydrazine (2) to give the intermediate hydrazone (3). Proton transfer leads to intermediate 4, which undergoes the key fragmentation to the alkyne (6) and the carbonyl compound (7).
The proton transfers from hydrazone (3) to intermediate (4) can be catalyzed by pyridine, sodium bicarbonate, sodium carbonate, or silica gel.
[edit] References
- ^ Eschenmoser, A. et al. Helv. Chim. Acta 1967, 50, 708-713. (DOI:10.1002/hlca.19670500232)
- ^ Schreiber, J., Felix, D.; Eschenmoser, A.; Winter, M.; Gautschi, F.; Schulte-Elte, K. H.; Sundt, E.; Ohloff, G.; Kalovoda, J.; Kaufmann, H.; Wieland, P.; Anner, G. Helv. Chim. Acta 1967, 50, 2101-2108. (DOI:10.1002/hlca.19670500747)
- ^ Tanabe, M., Crowe, D. F.; Dehn, R. L. Tetrahedron Lett. 1967, 3943-3946. (DOI:10.1016/S0040-4039(01)89757-4)
- ^ Felix, D.; Schreiber, J.; Ohloff, G.; Eschenmoser, A. Helv. Chim. Acta 1971, 54, 2896-2912. (Review)
- ^ Felix, D.; Wintner, C.; Eschenmoser, A. Org. Syn., Coll. Vol. 6, p.679 (1988); Vol. 55, p.52 (1976). (Article)
- ^ Dai, W.; Katzenellenbogen, J. A. J. Org. Chem. 1993, 58, 1900-1908. (DOI:10.1021/jo00059a049)
