FeCl3 catalysed multicomponent divergent synthesis of a library of indeno-fused heterocycles

Abstract

A simple, straightforward and versatile multicomponent synthetic protocol for indeno-fused heterocycles, namely diindeno[1,2-b:2′,1′-e]pyridine, indeno[1,2-b]quinoline and indeno[1,2-b]cyclopenta[e]pyridine derivatives, has been developed. The strategy involves the one pot three component reaction of enaminone, dialkyl but-2-ynedioate and 1,3-indanedione catalysed by FeCl₃ in acetonitrile under reflux. The presence of rotamers in the products with 2- and 3-substituted anilines as the amine component adds some interesting features to this expeditious domino reaction. In the course of the reaction, four new bonds (two C–C and two C–N bonds) and one stereocenter are formed in one operation. Mild reaction conditions, operational simplicity, wide substrate scope, product diversity and overall good yield make this reaction highly efficient for the library synthesis of indeno-fused heterocycles.