Abstract
The thermal reaction of 1‐substituted 2,3‐diphenylaziridines 2 with thiobenzophenone (6a) and 9__H__‐fluorene‐9‐thione (6b) led to the corresponding 1,3‐thiazolidines (Scheme 2). Whereas the cis‐disubstituted aziridines and 6a yielded only trans‐2,4,5,5‐tetraphenyl‐1,3‐thiazolidines of type 7, the analogous reaction with 6b gave a mixture of trans‐ and cis‐2,4‐diphenyl‐1,3‐thiazolidines 7 and 8. During chromatography on SiO~2~, the trans‐configured spiro[9__H__‐fluorene‐9,5′‐[1,3]thiazolidines] 7c and 7d isomerized to the cis‐isomers. The substituent at N(1) of the aziridine influences the reaction rate significantly, i.e., the more sterically demanding the substituent the slower the reaction. The reaction of cis‐2,3‐diphenylaziridines 2 with dimethyl azodicarboxylate (9) and dimethyl acetylenedicarboxylate (11) gave the trans‐cycloadducts 10 and 12, respectively (Schemes 3 and 4). In the latter case, a partial dehydrogenation led to the corresponding pyrroles. Two stereoisomeric cycloadducts, 15 and 16, with a trans‐relationship of the Ph groups were obtained from the reaction with dimethyl fumarate (14; Scheme 5); with dimethyl maleate (17), the expected cycloadduct 18 together with the 2,3‐dihydropyrrole 19 was obtained (Scheme 6). The structures of the cycloadducts 7b, 8a, 15b, and 16b were established by X‐ray crystallography.