Ultrasonically dispersed potassium, generated in toluene with an ultrasonic cleaning bath, was found to be efficient and regioselective for desulfonylation of cyclic sulfones. Sulfone functionality is of considerable synthetic importance. ' Most of its uses in synthesis ultimately involve the reductive cleavage of the sulfurcarbon bond to remove the sulfur atom from the target molecules. While various conventional reagents, including alkali metal amalgam, lithium in amines, Raney nickel, are effective for this purpose on aryl and some tertiary sulfones, 293 there are only limited reports in leterature about the desulfonylation of dialkyl or cyclic sulfones with low regioselectivity. 4 We now report that ultrasonically dispersed potassium is very convenient, efficient and regioselective for the reductive cleavage of C-S bond of cyclic sulfone systems. Cyclic sulfones were used in this study because, after the cleavage of C-S bond, the oxidation state of the sulfur could be easily examined and the results should be applicable to dialkyl sulfones.
Attempted desulfonylation of sulfolane 1 by treatment with metal potassium, taney nickel, sodium almalgam, sodium dithionite,5 or U/graphite, in this laboratory resulted in no reaction within reasonable period of time. While product from reaction with Li/EtNH2 was inconvenient to work up. It was later found that when 1 was treated with excess of ultrasonically potassium, generated in toluene in an ultrasonic bath7 the reaction took place immediately and the starting material was consumed in less than 4 hours.
The reaction was then quenched with excessive Me1 to give cleanly methyl butyl sulfone 3. Although butyl sulfinate 2 was assumed to be formed during the stage of the reductive stage, no efforts were made to isolate it owing to its high solubility in water. In addition to its high efficiency, this reaction is