The chemistry of 5-oxodihydroisoxazoles. XII. Trapping of derived ketenimines with lithium amides and alkyllithiums

Isoxazolones unsubstituted at C3 react with lithium amides or alkyllithiums to give ketenimines. The presence of an ethoxycarbonyl group at C4 allows capture of this species by addition of a second equivalent of the lithiated species to give enolates which can be alkylated in situ. The presence of a phenyl group at C4 gives a ketenimine which reacts intramolecularly in the presence of lithium amides, whereas alkyllithiums undergo addition in synthetically useful processes.