The Nicholas-type activation of cyclopropanes toward reactions with nitrones in the homo-[3+2]-dipolar cycloaddition

摘要

2-Ethynyl-1,1-carboethoxyclopropane, when treated with Co-2(CO)(8), results in the formation of the Co-2(CO)(6) adduct which in turn undergoes smooth cycloaddition in the presence of Sc(OTf)(3) to form the corresponding tetrahdyro-1,2-oxazines. The adducts can either be decomplexed to yield the parent acetylenes or made to undergo Pauson-Khand reactions to form 6-cyclopentenyltetrahydro-1,2-oxazines.