Dienediolates from unsaturated carboxylic acids: Michael addition of dilithium buta-1,3-diene-1,1-diolate (from crotonic acid) to unsaturated ketones

Abstract

Conjugate addition of the lithium dienediolate derived from crotonic acid to several α,β-unsaturated ketones gave 7-oxocarboxylic acids. Styrl ketones (2a–g) afforded mixtures of 1,4-α- and 1,4-γ-adducts, in proportions depending on the bulk of the substituents attached to the carbonyl group. The reaction with the styryl ketones occurs through a tandem 1,2-addition–oxy-Cope rearrangement mechanism. On the other hand, α- and β-methyl styryl phenones (2h and i) afforded 1,4-γ-products through 1,2-addition with subsequent retro-aldol and Michael-type addition.