Conjugated nitroalkenes in cycloaddition reactions. Part 2. Diels–Alder reactions of E-2-aryl-1-cyano-1-nitroethenes with cyclopentadiene

The reaction between E -2-aryl-1-cyano-1-nitroethenes 1a – 1e and cyclopentadiene ( 2 ) occurs according to the carbodiene [4+2]cycloaddition scheme and leads to the corresponding 6- endo -aryl-5- endo -cyano-5- exo -nitronorbornenes 3a – 3e and 6- exo -aryl-5- exo -cyano-5- endo -nitronorbornenes 4a – 4e as the only reaction products. The attempts to detect the products of heterodiene [4+2]cycloaddition in the reaction environment were not successful.