β-Lithiated enamines as enolate equivalents in Michael additions to enoates. A novel entry to mono- and disubstituted 5-oxo esters

Article abstract of DOI:10.1055/s-1991-26536

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 β-lithiated enamines to enoates, followed by quenching with water or iodomethane. In all cases, only one stereoisomer of the polysubstituted enamino esters 3 is produced (de > 98%).