1,4-dioxene in organic synthesis: Generation and reactivity of epoxydioxenes
作者:Christophe Baylon、Issam Hanna
DOI:10.1016/0040-4039(95)01307-4
日期:1995.9
Oxidation of various alkyldioxens with dimethyldioxirane is described. While pure epoxides were isolated from 4-dioxenylcyclohexanone 10 and diether 9, vinyldioxenes 11–14 gave the corresponding epoxide rearrangement products, α-ketal aldehydes 20–24, in excellent yields.
A highly diastereoselective synthesis of the taxane potential precursor 16 is achieved. An unexpected diastereoselectivity was observed upon condensation of the α-trimethylsilyloxyaldehydes 9a or 9b with the cyclohexenyllithium 10. The single diol isomers 13A and 14A exhibiting the required 1β,2α relative configuration are obtained in good yields.
A short and convenient way to produce the Taxol™ A-ring utilizing the Shapiro reaction
作者:Olli P Törmäkangas、Reijo J Toivola、Esko K Karvinen、Ari M.P Koskinen
DOI:10.1016/s0040-4020(02)00089-3
日期:2002.3
The Shapiro reaction was utilized in an efficient route to a Taxol(TM) A-ring building block. Commercially available 2-methyl-1,3-cyclohexanedione was converted in three simple steps to various arenesulfonylhydrazones and then to the target molecule with the Shapiro reaction. Remarkable differences were observed in the reactivity and stability of different hydrazones and their dianions in the Shapiro reaction. This pathway is the shortest one reported to give the target molecule in good overall yield. The use of different electrophiles in the final Shapiro reaction step allows alternative ways to prepare the target alcohol. (C) 2002 Elsevier Science Ltd. All rights reserved.