Regiospecific synthesis of biogenetically possible phenylpyrano[2,3-a] carbazolones

摘要

Reaction of 1-hydroxycarbazoles with phenylpropiolic acid in the presence of tritluroacetic acid led to the formation of a mixture of isomeric a-and y-pyrones, 2-and 4-phenylpyrano[2,3-a]carbazolones. Variation of reagents and reaction conditions, however, allowed the exclusive formation of either the a-pyrones orthe y-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.