Chan rearrangement
{{Short description|Chemical reaction}}
The Chan rearrangement is a chemical reaction that involves rearranging an acyloxy acetate (1) in the presence of a strong base to a 2-hydroxy-3-keto-ester (2).{{Ref|Chan}}
Image:Chan Rearrangement Scheme.png
This procedure was employed in the Holton Taxol total synthesis.{{Ref|Holton1}}
Reaction mechanism
The methylene bridge in the reactant with adjacent carbonyl and acetyl substituents is acidic and can be deprotonated by strong non-nucleophilic bases such as lithium tetramethylpiperidide or lithium diisopropylamide (LDA) as in an aldol reaction. The thus formed enolate then attacks the adjacent acetyl group through a short lived intermediate oxirane. Acidic workup liberates the free hydroxyl group.
See also
References
- {{Note|Chan}} Rearrangement of α-acyloxyacetates into 2-hydroxy-3-ketoesters S. D. Lee, T. H. Chan, and K. S. Kwon Tetrahedron Lett. 1984, 25, 3399-3402. ({{doi|10.1016/S0040-4039(01)91030-5}})
- {{Note|Holton1}} First total synthesis of taxol 1. Functionalization of the B ring Robert A. Holton, Carmen Somoza, Hyeong Baik Kim, Feng Liang, Ronald J. Biediger, P. Douglas Boatman, Mitsuru Shindo, Chase C. Smith, Soekchan Kim, et al.; J. Am. Chem. Soc. 1994, 116(4), 1597-1598. ({{doi|10.1021/ja00083a066}})
Category:Carbon-carbon bond forming reactions