反应详情

Heated solutions of dimethyl sulfoxide (DMSO) can dehydrate secondary or tertiary alcohols. Heating 65 grams of alcohol (E) (0.30 moles) in 65 ml of DMSO at 190° C. for ninety minutes resulted in the rapid formation of acetates (B) and (G). The reaction mixture was cooled to 0° C. and then poured into an equal volume of water. The resulting mixture was then extracted with three 200 ml portions of tert-butyl methyl ether. The combined ethereal extracts were washed with brine, dried over anhydrous magnesium sulfate, filtered and concentrated to afford 52 grams of a crude oil. NMR analysis indicated this oil to consist of a 5:1 mixture of (B) to (G) respectively. Although the dehydration yield was consistently greater than 85%, hot DMSO generated various foul smelling vapors that could not be identified nor prevented. The addition of inorganic bases such as barium or calcium oxide suppressed the decomposition of dimethyl sulfoxide but also retarded the rate of dehydration. This reaction is amenable to a large scale process that is in quantities greater than 250 grams.