Sulphonates, Cyclic Sulphinates, and Related Systems

Cyclic Sulphonates, Cyclic Sulphinates, and Related Systems.—A valuable new method of synthesizing 1,2-oxathiolan 2,2-dioxides and 1,2-oxathian 

2- dioxides involved treatment of suitable alkanesulphonate esters of 

2- and 1,3-diols, respectively, with one equivalent of butyl-lithium. The formation of 6-methyl-l,2-oxathian 2,2-dioxide in good yield from 

2- oxathian 2-oxide systems by n.m.r. and dipole-moment data. Oxidation of the 3,5-diphenyl-l,2-oxathiolan 2-oxides to the 2,2-dioxides was attended by a slight flattening of the ring and a considerable enhancement of conformational mobility. In an analogous case, 1,2-oxathian 

2- dioxide underwent rapid chair-chair interconversion at — 90°C according to n.m.r. data, but 1,2-oxathian 2-oxide appeared to be locked in the chair conformation with sulphinyl oxygen axial in the temperature range - 90 to -f- 150 illustrating further the strong preference for the axial orientation of sulphinyl oxygen.  

---