INTRAMOLECULAR CONJUGATE ADDITION-REACTIONS VIA ORGANOZINC COMPOUNDS

This paper describes the application of organozinc compounds in a gene ral strategy for achieving intramolecular conjugate addition with nons tabilized carbanion derivatives. Organozinc iodides, prepared by the r eaction of the corresponding organoiodides with activated zinc metal, undergo an intramolecular 1,4-addition reaction with alpha,beta-unsatu rated ketones and esters to form five- and six-membered-ring products. A mechanistic study suggests that, at most, only a small part of the cyclization product can result from a radical-mediated pathway. Both o lefinic and acetylenic unsaturated carbonyl compounds participate in t he intramolecular conjugate addition reaction. Addition of electrophil ic reagents such as methyl iodide and acetaldehyde permits the in situ synthetic elaboration of the product enolates.