反应详情

A mixture of the cis and trans isomers of ethyl 5-hydroxytetrahydropyran-2-carboxylate (3.9 g, 0.023 mol) was dissolved in dry toluene (200 ml). p-Toluene-sulfonic acid monohydrate (0.20 g, 1.1 mmol) was added as a catalyst. The mixture was refluxed for 7 hours through a Soxhlet extractor containing molecular Type A sieves in a thimble. The mixture was cooled to room temperature, and anhydrous sodium carbonate (5 g) was added to neutralize the acid. The solution was passed through a short pad of silica gel and concentrated. A brown viscous oil was subjected to column chromatography (column, silica gel; eluent, n-hexane/ethyl acetate, 1:1 v/v). The crude product thus isolated was purified by repeated recrystallization from a mixture of ethyl ether and n-hexane (5-20:1 v/v). The lactone has a melting point of 56°-57° C.

1. temperatureThe mixture was refluxed for 7 hours through a Soxhlet extractor
2. additioncontaining molecular Type A sieves in a thimble
3. concentrationconcentrated