Competitive [3+2] and [4+2] cycloaddition reactions of 2-furaldehyde phenylhydrazone with alkenes
Maleimides react with 2-furaldehyde phenylhydrazone 1 at the furan ring to give 4-(phenylhydrazono)methyl-1H-isoindole-1,3(2H)-diones when equimolar mixtures are refluxed in benzene for shorter reaction times. Excess maleimides and longer reaction times give mixtures of 4- (phenylhydrazono)methyl-1H-isoindole-1,3(2H)-diones and 3-(1,3-dihydro-1,3- dioxo-4-isoindolyl)-1,6a-dihydropyrrolo[3,4-c]pyrazolo-4,6(3aH,5H)-diones resulting from [4 + 2] and [3 + 2] double-cycloaddition. Reactions of 1 with dimethyl acetylene dicarboxylate give the double-cycloaddition product dimethyl-3[4-hydroxy-2,3-bis(methoxycarbonyl)phenyl]-1-phenylpyrazole-4,5- dicarboxylate. Methyl acrylate and acrylonitrile gives only the [3 + 2] cycloaddition products, 3-(2-furyl)-1-phenyl-4,5-dihydropyrazole-4-carboxylic methyl ester and 3-(2-furyl)-1-phenyl-4,5-dihydropyrazole-4-carbonitrile, respectively.
Amarasekara, A., & Pathmasiri, W. (2000). Competitive [3+2] and [4+2] cycloaddition reactions of 2-furaldehyde phenylhydrazone with alkenes. Retrieved from https://digitalcommons.pvamu.edu/chemistry-physics-facpubs/114