ALLYLIC SUBSTITUTION BY CARBON NUCLEOPHILES ON 4-BROMO-4-METHYL-2-PENTENOATE: ANTI-MICHAEL REGIOSELECTIVITY.

Article abstract of DOI:10.1016/S0040-4020(01)86691-6

The reaction of carbanions α-to nitriles with tertiary bromoester 1 does not give cyclopropanes, whatever the reaction conditions, while Li enolate of methyl phenylacetate does, in THF or THF-Et2O.From lithiated aminonitriles 5, in THF-HMPA, the reaction leads to a mixture of S_N and S_N' products in equal amounts via a radical process.From arylaceto- and propionitriles 4 whatever the conditions, and from methyl phenylacetate enolate 16, either associated to Li in THF-HMPA or to K in THF, S_N' anti-Michael products are predominantly formed via a concerted inner sphere process, showing thus the possibility of a polar-SET mechanistic spectrum from a single electrophilic reagent.