Diels-Alder Reactions between Acrolein N,N-Dimethylhydrazone and N-Benzylated Benzotriazole-, Indazole- or Indole-4,7-diones

Abstract

Diels-Alder reactions between acrolein N,N-dimethylhydrazone 4 and N-benzylated benzotriazole, indazole and indole-4,7-diones 1, 2 and 3 afforded new heterotricyclic quinones 5, 7 and 9 including from 2 to 4 intracyclic nitrogen atoms. A structural assignment of all new compounds was achieved using 2D NMR 1 H- 13 C HMBC correlations. The single 1,8- regioisomer was isolated starting from benzotriazole or indazole quinones, while a mixture of the 1,5- and 1,8- regioisomers was obtained from an indole-4,7-dione derivative. In all cases, the observed regiochemistry was in agreement with FMO calculation.