The 2-Phenylselenenylation of 2-Enoic Esters

Abstract

During work directed at developing a method for the α-alkylation of α,β-unsaturated carbonyl compounds, we had occasion to study the reactions of the ester enolate anions 2, derived from the Michael addition of lithium di-isopropylamide (LDA) on α,β-unsaturated esters 1. Quenching these anions with phenylselenenyl bromide gave products 3 directly, presumably via elimination from 4 (R' = SePh).

The overall sequence as depicted above is evident from the isolation of uneliminated products 4a-c from the addition of appropriate electrophiles to 2. Also, an alternative route to 3 involving the formation¹ from 1 of the β,γ-unsaturated ester enolate 5, selen-enylation and proton shift is unlike since control experiments with β,γ-unsaturated esters as starting materials gave δ-selenenyl-α,β-unsaturated esters (8 and 16, Table), presumably via α-proton