Synthesis of [1]Benzopyrano[4,3-b]pyrrol-4(1H)-ones from 4-Chloro-3-formylcoumarin

Abstract

2-Functionalized [1]benzopyrano[4,3-b]pyrrol-4(1H)-ones were obtained by the Fischer-Fink reaction starting from 4-chloro-3-formylcoumarin and different α-amino derivatives (e.g. glycinonitriles, ethyl glycinates and α-amino ketones). In general limitations to the synthetic method arise when α-amino derivatives with very reactive functions were used (e.g. carboxaldehyde groups or their acetal derivatives) leading to Knorr type reactions, or when they contain relatively inactive methylenes (e.g. carboxamide groups) which failed to complete the cyclization process.