Synthesis, configuration, and conformation of 3-acyl derivatives of 3a,4,6,6a-tetrahydrothieno[3,4-d][1,2,3]oxathiazoline 2-oxide

Abstract

3-Benzoyl-3a,4,6,6a-tetrahydrothieno[3,4-d][1,2,3]oxathiazoline 2-oxide is formed as a result of intramolecular cyclization of cis-4-benzamido-3-chlorosulfitothiophan. Only one sulfur atom — that of the sulfoxide group — is removed from the cyclization product and the analogous 3-methoxycarbonyl-3a,4,6,6a-tetrahydrothieno[3,4-d][1,2,3]oxathiazoline 2-oxide by the action of Raney nickel; the products in this case are, respectively, cis-4-benzamido-3-hydroxythiophan and 3a,4,6,6a-tetrahydrothieno]3,4-d]oxazolidone. The three-dimensional structure of 3-acyl-3a,4,4,6a-tetrahydrothieno[3,4-d][1,2,3]oxathiazoline 2-oxide was determined by ¹H and ¹³C NMR spectroscopy. A difference between the conformational state of 3-substituted 3a,4,6,6a-tetrahydrothieno[3,4-d][1,2,3]oxathiazoline 2-oxides and 3-substituted 3a,4,6,6a-tetrahydrothieno[3,4-d]oxazolidones was established.