Romanski, Jaroslaw; Mloston, Grzegorz; Linden, Anthony; Heimgartner, Heinz (1999). A novel type of ring closure af amino-substituted thiocarbonyl ylides. Polish Journal of Chemistry, 73:475-485.
The reaction of 4,4-dimethyl-1,3-thiazole-5(4H)-thiones 7a-c with dimethyl 2-diazo-3-(phenylamino)butanoate (2), prepared from dimethyl fumarate and phenyl azide, in toluene at 80°C yielded mixtures of dimethyl 2-(4,5-dihydro-4,4-dimethyl-1,3-thiazol-5-ylidene)-3-(N-phenylamino)butanedioates of type 11 and four diastereoisomeric 4,4-dimethyl-9-phenyl-1,6-dithia-3,9-diazaspiro[4.4]non-2-ene-7,8-dicarboxylates of type 12. The formation of the products of type 12 is rationalized by a novel cyclization of intermediate thiocabonyl ylides 9. The structures of cis-12a, cis-12c, and trans-12c were established by X-ray crystallography.