Syntheses of optically active 2-(2-benzothiazolylimino)-heterazolidines

The syntheses of compounds 4R, 5R-2-[2-benzothiazolylimino]-3-hydro-4-methyl-5-phenylthiazolidine (5a), 4S,5S-2-[2-benzothiazolylimino]-3-, 4-dimethyl-5-phenylthiazolidine (5b), 4R,5S-[2-benzothiazolylimino]-3-hydro-4-methyl-5-phenyloxazolidine (5c), 4R,5S-2-[2-benzothiazolyl-imino]-3, 4-dimethyl-5-phenyloxazolidine (5d), and 4R,5S-2-[2-benzothiazolylimino]-1,3,4-trimethyl-5-phenylimidazolidine (5e) are reported. The stereochemistry of the reaction products and the X-ray diffraction analyses of compounds 5a-d are discussed. Compounds 5a-d present planar structures. We have found short distances between the thiazolidine S1 atom and the benzothiazole N9 atom for 5a and 5b (2.782 and 2.824 Å, respectively) and the distance between the oxazolidine O1 and the benzothiazole S7 for 5d (2.721 Å). These distances are shorter than the sum of the van der Waals radii. These distances, together with the coplanarity of the heterocycles, seem to indicate the existence of a weak coordination bonding from sp² oxygen or nitrogen atoms towards the sulfur atom.