SYNTHESIS AND REACTIONS OF FURO[1,3-B]PYRROLES

Methyl 6H-furo[2,3-b]pyrrote-5-carboxylate (2a) was prepared by thermo lysis of the corresponding methyl 2-azido-3-(3-furyl)propenoate (1). 6 -Methyl (2b) and 6-benzyl (2c) derivatives were obtained using phase-t ransfer catalysis conditions (PTC). The formylation of 2a-2c gave 2-fo rmylated compounds (3a-3c). Compounds 4b, 4c were prepared by reaction s of corresponding esters 2b, 2c with hydrazine in refluxing ethanol. By reaction of 3a-3c with hydroxylammonium chloride in acetic anhydrid e in the presence of pyridine, methyl 2-cyano-6-R-1-furo[2,3-b]pyrrole -5-carboxylates (5a-5c) were obtained. The reaction of these compounds with sodium azide and ammonium chloride in dimethylformamide led to m ethyl etrazolyl)-6-R-1-furo[2,3-b]pyrrole-5-carboxylates (6a-6c). A se ries of xycarbonyl-6-R-1-furo[2,3-b]pyrrole-2-carbaldehyde N,N-dimethy lhydntzones (7a-7c) was prepared from methyl 2-formyl-6-R-1-furo[2,3-b ]pyrrole-5-carboxylates (3a-3c) and unsym-dimethylhydrazine. The corre lation of the C-13 and N-15 chemical shifts with the data of the calcu lated (AM1) net atomic charges is discussed.