An Efficient One-pot Synthesis of Pyrano[3,2-c]carbazole and Pyrano [2,3-a]carbazole Derivatives

A new method has been developed for the synthesis of pyrano[3,2-c] and pyrano[2,3- a]carbazole derivatives via a three-component reaction of 4-hydroxycarbazole or 2-hydroxycarbazole, aromatic aldehydes, and arylenaminones. This transformation presumably occurs via Knoevenagel condensation, Michael addition, o-cyclization, elimination, and isomerization sequence of reactions. Noteworthy features of this protocol include easy isolation, good functional group tolerance, and high yields.