Chemistry of beta-functionalized alpha-nitroso ethylenes. Methyl beta-nitroso acrylate as heterodienophile in [4+2]cycloaddition to cyclic dienes

beta-Functionalized nitroso alkene 2, obtained from methyl beta-nitropropio nate 1 and N,O-bis(trimethylsilyl)acetamide, can function as a good heterod ienophile in Diels-Alder reactions, Therefore, 2 was trapped by cyclic dien es to give adducts 4 with the corresponding stereoselectivity, Cycloadduct 4a undergoes retro[4 + 2]-cycloaddition at 33 degrees C in solution; thus 4 a can be used to generate nitroso alkene 2 in neutral medium. Cyclopentadie ne reacts with adduct 4a according to an endo-[4 + 5]-cycloaddition scheme to give cycloadduct 5 in low yield.