Nitriles in heterocyclic organic synthesis: Synthesis of pyrano[2,3-h]coumarines, pyrano[3,2-c]coumarines, and their derivatives

Several new 4H-pyrano[2,3-h]coumarines 5a-e were prepared by the reaction o f 7-hydroxycoumarine with cinnamonitriles 1. Also, the reaction of 7-hydrox ycoumarine with a mixture of aliphatic aldehydes and malononitrile afforded compounds 5f,g. Similarly, 4-hydroxycoumarine was reacted with the same re agents to give compounds 9a-g. The reaction of 9 g with different nucleophi lic reagents afforded the pyrimido[ 4',5' :6,5]pyrano [3,2-c]coumarin-4-one derivatives 10-12, 4-methyl-2(ethoxymethylenamino)4H-pyrano itrile (13) an d pyrazolo[3',4';6,5]pyrano[3,2-c]coumarin (14) respectively.