Organosulfur Chemistry. II. Use of Dimethyl Sulfoxide; a Facile Synthesis of Cyclic Sulfides

Abstract

A versatile and short-reaction-time synthesis of twelve four-, five- and six-membered thiacycloalkanes (IIa-l) from the appropriate α,ω-dibromoalkanes (Ia-l) has been developed. Technicalgrade dimethyl sulfoxide was proved to be by far the best for this cyclization. The pronounced effect for ring formation was recognized to be in order of five-membered ring (thiolanes)>six-membered ring (thiolanes)>six-membered ring (thianes)>four-membered ring (thietanes). Startling were 2-methylthiolane (IIf) and 2,5-dimethylthiolane (IIg; cis,trans mixture), both obtained in high yields although α-methyl- and α,α'-dimethyl substitution in general showing a remarkable retardation for cyclization. On the other hand, in both 3,3-dimethylthietane (IId) and 4,4-dimethylthiane (IIl) cyclization was much more efficient than other counterparts in each series, which is referred to as the gem-dimethyl effect. © 1985, The Pharmaceutical Society of Japan. All rights reserved.