反应详情

25 ml of isobutylene were condensed at −78° C. and added to a mixture of 19.4 g (114 mmol) of 3(RS),7-dimethyl-6-octenoic acid and 1 ml of concentrated sulphuric acid in 25 ml of dichloromethane. The mixture was stirred for 24 hours under a dry ice condenser. A further 20 ml of isobutylene were added and the mixture was stirred for 24 hours under a dry ice condenser. The mixture was diluted with dichloromethane, washed with saturated sodium bicarbonate solution, dried over anhydrous magnesium sulphate and evaporated under a vacuum. The resulting oil was purified by chromatography on silica gel using ethyl acetate/hexane (1:9) for the elution. There were obtained 20.8 g of tert-butyl 3(RS),7-dimethyl-6-octenoate as a colourless oil. 1H NMR (250 MHz, CDCl3)δ: 0.9 (d, 3H), 1.1-1.3 (m,3H), 1.4 (s, 9H), 1.6 (s, 3H), 1.65, (s, 3H), 1.8-2.2 (br m, 4H), 5.05, (m, 1H).

1. customcondensed at −78° C.
2. stirringthe mixture was stirred for 24 hours under a dry ice condenser
3. washwashed with saturated sodium bicarbonate solution
4. dry with materialdried over anhydrous magnesium sulphate
5. customevaporated under a vacuum
6. customThe resulting oil was purified by chromatography on silica gel
7. washfor the elution