REACTION OF DIETHYLAMINOSULFUR TRIFLUORIDE WITH DIOLS

Diethylaminosulfur trifluoride (DAST) reacts with dialcohols to give d ifluorides, sulfite esters or cyclic ethers depending on the number of carbons separating the two alcohol groups. Vicinal and 1,3-diols give large amounts of sulfite ester products while butane-1,4-diol gives a lmost exclusively the cyclic ether tetrahydrofuran. Terminal dialcohol s longer than four carbons give primarily difluoride products. Semiemp irical calculations indicate a preference for cyclic intermediates whe n four or less carbons separate the two alcohol moieties. These cyclic intermediates lead directly to the cyclic ethers and sulfite ester pr oducts.