Palladium(0)-Catalyzed Allylic Substitution with Allylic Alkoxides as Substrates

Article abstract of DOI:10.1016/S0040-4020(01)80774-2

A new method has been developed which allows palladium(0)-cayalyzed allylic substitution to occur between allylic alcohols and anionic C-nucleophiles: on reaction with Ph3B, the allylic alkoxide 2 is first converted in situ into the more reactive species 3 which then undergoes a Pd(0)-catalyzed reaction with lithio diethyl malonate via the η³-complex 6.Allylic alkoxides can be generated in situ either by deprotonation of the corresponding alcohol (1 -> 2, e.g. with BuLi), via a vinylmagnesium haalide addition to the corresponding aldehyde (4 + 5 -> 2), or by hydride reduction (DIBAH) of α,β-unsaturated ketones (31 -> 32).The whole sequence can be carried out as a one pot procedure and is suitable for sensitive allylic alcohols that might be difficult to handle in pure state.While primary allylic alcohols (7 and 18) and their allylic isomers (14 and 15) give mixtures of mono- and bis-allylated products with LiCH(CO2Et)2, exclusive monoallylation has been observed for secondary alcohols (21, 23, and 26).