Intramolecular diels-alder reactions. IX. Syntheses of N-benzylcyclolignan lactams

Four bis-unsaturated N-benzyl amides of the type where (C₂) and (C₂)' are variously trans-CH?CH and C?C groups, were synthesized and refluxed in acetic anhydride. Three of them cyclized to form N-benzylcyclolignan lactams by intramolecular Diels-Alder processes. In one case [(C₂) ? C?C, (C₂)' ? trans-CH?CH] the (C₂) unit functioned as the dienophilic moiety.