Preparation and Rearrangement of cis-Methyl 3,4-Epoxy-4-(4'-methylphenyl)butanoate
AlCl3 catalysed bromination of methyl 4-keto-4-(4'-methylphenyl)butanoate (2) is regioselective and furnishes methyl 3-bromo-4-keto-4-(4'-methylphenyl)butanoate (3). 3 on NaBH4 reduction in the presence of NaHCO3 furnishes a mixture of cis-methyl 3,4-epoxy-4-(4'-methylphenyl)butanoate (9), methyl (E)-4-hydroxy-4-(4'-methylphenyl)but-2-enoate (12), 4-(4'-methylphenyl)butanolide (26) and 2. 12 can be transformed to 1 on heating with NaOH-ethanol.BF3 catalysed rearrangement of 9 furnishes methyl 3-keto-4-(4'-methylphenyl)butanoate (17).The sequence of reactions 2->3->9->17 constitutes an interesting example of ketone transposition and provides a convenient route for the preparation of 17 from the readily available 2.
Bhat, K. S.,Rao, A. S.
p. 355 - 358
(2007/10/02)
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