Syntheses of [1]Benzopyrano[4,3-c]pyrazoles and -[3,4-d]isoxazoles

The reaction of 2H-1-benzopyran with several 1,3-dipoles gives cycloadducts in good yields. The orientation of the cycloaddition is qualitatively interpreted in terms of FMO theory. These heteropolycyclic compounds were also obtained from hydrazones of 3-aroyl-2H-1-benzopyrans, prepared from 3-cyano-2H-1-benzopyran.