Nguyen Dinh Nguyen Dinh An

Regiochemistry of the cycloadditions of diphenylnitrilimine to coumarin, 3-ethoxycarbonyl and 3-acetyl coumarins: A reinvestigation

Abstract The cycloaddition reactions of diphenylnitrilimine to coumarin, 3-ethoxycarbonyl and 3-acetylcoumarins were studied. The observed regiochemistry of the reaction with the coumarin 4a was the same as the one suggested by other researchers. For the coumarins 4b and 4c bearing an electron withdrawing group at the 3-carbon atom, our results invalidate the previously reported regiochemistry. The presence of an electron-withdrawing group at the 3-C atom of coumarin derivatives reverses the regioselectivity of cycloaddition of diphenylnitrilimine to the dipolarophilic double-bond.