β-Lithiated Enamines as Enolate Equivalents in Michael Additions to Enoates. A Novel Entry to Mono- and Disubstituted 5-Oxo Esters

Abstract

Mono-, di- and trisubstituted tert-butyl 5-amino-4-alkenoates 3 and mono- or disubstituted tert-butyl 5-oxoalkanoates 4 are prepared in good overall yield by conjugate addition of ß-lithiated enamines to enoates, followed by quenching with water or iodo-methane. In all cases, only one stereoisomer of the polysubstituted enamino esters 3 is produced (de > 98%).