反应详情

A solution of diols from Example 1d (3.0 g, ˜6.5 mmol of the main diastereomeric pair of enantiomers of 5a), 2,2-dimethoxypropane (4.0 g, 0.38 mol) lithium bromide (0.1 g) and p-toluenesulfonic acid (0.1 g) in THF (40 ml) was stirred at r. t. for 2 h, then poured onto saturated aqueous sodium bicarbonate solution (100 ml) and extracted with MTBE (2×100 ml). The combined organic phases were washed with water (2×100 ml), dried (Na2SO4), concentrated in vacuo and the residue (3.0 g) purified by flash chromatography (MTBE/hexane 1:20) to afford a mixture of isomeric diols (0.60 g, colourless oil) in which the main diastereoisomeric pair of enantiomers of 2,2,6,6,10,10-hexamethyl-5,7-dioxatetracyclo[9.2.1.01.9, 04.8]tetradecane (Ia) constituted 73% (24% yield).

1. extractionextracted with MTBE (2×100 ml)
2. washThe combined organic phases were washed with water (2×100 ml)
3. dry with materialdried (Na2SO4)
4. concentrationconcentrated in vacuo
5. customthe residue (3.0 g) purified by flash chromatography (MTBE/hexane 1:20)
6. customto afford