Chemoselectivity of the Reactions of Diazomethanes with 5-Benzylidene-3-phenylrhodanine

摘要: The reactions of 5-benzylidene-3-phenylrhodanine (2; rhodanine = 2-thioxo-1,3-thiazolidin-4-one) with diazomethane (7a) and phenyldiazomethane (7b) occurred chemoselectively at the exocyclic C=C bond to give spirocyclopropane derivatives 9 and, in case 7a, also C-methylated products 8 (Scheme 1). In contrast, diphenyldiazomethane (7c) reacted exclusively C=S group leading 2-(diphenylmethylidene)-1,3-thiazolidine 11 via [2+3] cycloaddition a two-fold extrusion reaction. Treatment or 9b an excess 7a refluxing CH2Cl2 THF room temperature presence [Rh2(OAc)4], respectively, led 1,3-thiazolidine-2,4-diones 15 20, respectively, i.e., hydrolysis intermediate thiocarbonyl ylide. On other hand, 7b 7c boiling toluene yielded corresponding 2-methylidene 16, 21a, 21b. Finally, reaction electron-poor C=C bond, which is conjugated C=O group. addition 23, 22 was formed as minor product. structures (Z)-8, 9a, 9b, 11, 23 were established by X-ray crystallography.