Inter-and Intramolecular [4 + 2] Cycloadditions of Nitroalkenes with Olefins. 2-Nitrostyrenes

Aromatic nitroalkenes 9-12 underwent Lewis acid catalyzed cycloadditions with various cyclic alkenes to afford high yields of nitironates 25-30 with exclusive anti selectivity. Hammett studies helped to further delineate the role of the Lewis acid. Reaction of nitroalkenes 8 and 10 with various cyclic dienes in the presence of a Lewis acid demonstrated the ability of nitroalkenes to behave as dienes in cycloadditions. The major products were the syn diastereomers which arise from an endo-folded transition structure. Finally, intramolecular cycloaddition of 36-39 allowed a correlation between the stereochemical course of the reaction and positions of sp² centers in the tether to be addressed.