Lewis acid–mediated reactions of propargyl chalcogenides with ethyl glyoxylate.

The [3+2] cycloaddition reaction of mesityl propargyl sulfide with ethyl glyoxylate was found to occur by using tin(IV) chloride to give a 2,5-dihydrofuran derivative. On the other hand, when 3-silyl propargyl sulfides were used, allyl alcohols were obtained. In the case of propargyl sulfides possessing dimethyl groups at the α-position of the propargyl group, cycloaddition products were obtained even if a silyl group was present on the propargyl group. In addition, mesityl propargyl selenides also reacted with ethyl glyoxylate by using tin(IV) chloride to give the corresponding [3+2] cycloaddition products. [ABSTRACT FROM PUBLISHER]