Regioselective synthesis of [1]benzopyrano[4,3-c]pyrazol-4-(1H)-one and [1]benzopyrano[3,4-c]pyrazol-4(3H)-one derivatives

The cycloaddition reaction of N-phenyl-C-cinnamonitrilimine4 to coumarin leads to the formation of 3-styrylbenzopyrano[4,3-c]pyrazole derivative6, whereas 3-phenylsulfonylcoumarin 0163 0181 V 39 or 3-bromocoumarin10 or 3-cyanocoumarin11 gives 1-styrylbenzopyrano[3,4-c]pyrazole derivative7. Also, the cycloaddition of4 to 3-acetylcoumarin15 and 3-benzoylcoumarin16 gives the corresponding dihydropyrano[3,4-c]pyrazole adducts17 and18 respectively. Oxidation of17 and18 gives7.