Treatment of N-benzyl 1,2,3,4-tetrahydroisoquinoline-1-carboxylate with sodium hydride in N,N-dimethylformamide gives the corresponding N-benzyl 1,2,3,4-tetrahydroisoquinolin-1-one in quantitative yield. The N-benzyl 1,2,3,4-tetrahydro-β-carbolin-1-one is prepared in a similar fashion. The N-deprotection occurred concomitantly with the oxidative decarboxylation when the nitrogen was benzyloxycarbonylated. © 2001 Elsevier Science Ltd.