Studies on pyrrolidinones. On the carbamoylation of some pyroglutamic derivatives

The carbamoylation of some lactams derivatived from pyroglutamic acid as been studied; better yields were obtained starting from the unsubstitued lactam (toluene, 80 degrees) rather than starting with the N-silyllactam (room temperature), although these latter reaction conditions could be interesting for heat sensitive compounds. Methyl and phenyl isothiocyanate react only with the sodium salt of methyl pyroglutamate, giving 1,5-diaddition products.