p-Toluenesulfonic acid → Tetrahydro-2-(2-propynyloxy)-2H-pyran

Participants

Reaction Conditions

Reaction Steps

To a stirred solution of 112 g. (2.0 mol.) of 3-hydroxy-1-propyne and 260 g. (3.0 mol.), of dihydropyran in 1.20 1. of methylene chloride cooled to 0° C. in an ice bath, is added a solution of 20 mg. of para-toluenesulfonic acid in 100 ml. of methylene chloride, dropwise. The reaction mixture is stirred at 0° C. for one-half hour, and at ambient temperature for one hour. It is then poured into 200 ml. of a 5% solution of sodium bicarbonate, the organic phase is separated, the aqueous phase extracted with 100 ml. of methylene chloride, the combined organic phases washed with 100 ml. of a solution of brine, dried over sodium sulfate, and evaporated under vacuum (12 mm.) at 45° C., to give 300 g. of crude product, which is purified by fractional distillation, b,p, 71°-73° C. (14 mm.) to yield 250 g. (89%) of a liquid.

Provenance & Evidence