PALLADIUM(0)-CATALYZED ALLYLIC SUBSTITUTION WITH ALLYLIC ALKOXIDES ASSUBSTRATES

A new method has been developed which allows palladium(0)-catalyzed al lylic substitution to occur between allylic alcohols and anionic C-nuc leophiles: on reaction with Ph(3)B, the allylic alkoxide 2 is first co nverted in situ into the more reactive species 3 which then undergoes a Pd(0)-catalyzed reaction with lithio diethyl malonate via the eta(3) -complex 6. Allylic alkoxides can be generated in sine either by depro tonation of the corresponding alcohol (1 --> 2, e.g. with BuLi), via a vinylmagnesium halide addition to the corresponding aldehyde (4 + 5 - -> 2), or by hydride reduction (DIBAH) of alpha,beta-unsaturated keton es (31 --> 32). The whole sequence can be carried out as a one-pot pro cedure and is suitable for sensitive allylic alcohols that might be di fficult 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(CO(2)Et)(2), exclusive monoallylation has been observed for secondary alcohols (21, 23, and 26).