Abstract
Thermal reactions of 1,2,3-trisubstituted ariridines 1 with 1,3-thiazole-5(4H)-thiones 6 in toluene yielded, in general, a mixture of two diastereoisomeric spirocyclic [2+3] cycloadducts. The formation of these products can be explained by a stereoselective electrocyclic ring opening of 1 to give an azomethine ylide 2 as the reactive intermediate, which is trapped immediately by 6 via a stereoselective 1,3-dipolar cycloaddition. Only in the case of trans-dimethyl 1-(4-methoxyphenyl)aziridine-2,3-dicarboxylate (trans-la), four diastereoisomeric cycloadducts were formed (Scheme 4). This result is rationalized by an isomerization of the intermediate azomethine ylide cis-2a to trans-2a.
Mlostoń, Grzegorz