Diels-Alder reaction of 2-cyano-1-azadienes. The effect of nitrogen substituents

The Diels-Alder reactions of 2-cyano-1-aza dienes with three nitrogen substituents possessing different electronic requirements (phenyl, CO 2 C 2 H 5 , and OCH 3 ) were studied with three dienophiles with different electronic requirements (styrene, methyl acrylate, and ethyl vinyl ether). The N-phenyl substituent aza diene was equally reactive with all three dienophiles. The N-CO 2 C 2 H 5 -substituted aza diene behaved as an electrophilic diene being more reactive with the electron-rich ethyl vinyl ether than styrene or methyl acrylate. The N-CO 2 C 2 H 5 -substituted aza diene is more reactive with all three dienophiles, including methyl acrylate, than the N-phenyl substituent azadiene; The N-OCH 3 -substituted aza diene was unreactive with all three dienophiles under the conditions investigated