Regiospecific synthesis of Biogenetically Possible Phenylpyrano[2,3-A] carbazolones

Abstract

Reaction of 1-hydroxycarbazoles with phenylpropiolic acid in the presence of trifluroacetic acid led to the formation of a mixture of isomeric α- and γ-pyrones, 2- and 4-phenylpyrano[2,3- a]carbazolones. Variation of reagents and reaction conditions, however, allowed the exclusive formation of either the α–pyrones or the γ-pyrones in high yields. A single crystal X-ray structure was determined for one of the novel α-pyrones, 4-phenylpyrano[2,3-a]carbazol-2-one.