Desulfurilative self-coupling reaction of 1,3-thiazolidine-2-thiones and intramolecular non-bonded S center dot center dot center dot S interaction in the crystallographic structure of the products

An attempt at an asymmetric Pummerer-type reaction of trans-4-benzyloxythia ne-1-oxide (1) with 3-trifluoroacetyl-4S-isopropyl-1,3-thiazolidine-2-thion e (2) resulted in failure but an attractive desulfurilative self-coupling r eaction of 4S-isopropyl-1,3-thiazolidine-2-thione (6) occurred to give 4S-i sopropyl-3-(4S-isopropyl-1,3-thiazolin-2-yl)-1,3-thiazolidine-2-thione (5). The same desulfurilative self-coupling reaction of compound 6 or 11 effici ently proceeded by treatment of diphenyl sulfoxide (7a) or methyl phenyl su lfoxide (7b) with 2 or 3-trifluoroacetyl-1,3-thiazolidine-2-thione (8) to a fford each corresponding product 5 or 9. Eventually, we found a practically useful method for the synthesis of 5 and 9 by exploiting TiCl4 and sodium salt 12 or 13 of 1,3-thiazolidine-2-thiones. Interestingly, intramolecular non-bonded S ... S interactions were recognized in the crystallographic str uctures of 5 and 9. (C) 2000 Elsevier Science S.A. All rights reserved.