反应详情

Into a reaction vessel, a solution of 4-hydroxy-4-methyl-5-allyl-2-cyclopentenone (3 g) and MgCl2.6H2O (4.0 g) in water (120 ml) was charged, and the temperature was elevated up to 100° C. The contents were adjusted to pH 7.3 with 0.1 N NaOH solution, and stirring was continued at 100° C. for 4 hours, during which the pH was maintained at 7.0 to 7.3. After cooling, NaCl (40 g) was added to the reaction mixture, and the resultant mixture was extracted with ether (120 ml) 4 times. The extracts were combined together, dried over anhydrous magnesium sulfate and concentrated at 40° C. under reduced pressure to give an oily substance (2.7 g). The oily substance was chromatographed with silica gel (30 g), followed by development with a solvent mixture of ethyl acetate and hexane (1:2 by volume) to give 2-allyl-3-methyl-4-hydroxy-2-cyclopentenone (2.6 g). Yield, 87%. N.M.R. (CDCl3, internal standard TMS, δ ppm, 90 MHz): 5.71 (complex m, 1H, --CH2 --CH=CHaHb); 5.06 (m, 1H, --CH2 --CH=CHaHb); 4.93 (m, 1H, --CH2 --CH=CHaHb); 4.74 (broad d, 1H, 4-H); 3.94 (broad s, 1H, 4-OH); 2.96 (d, 2H, --CH2 --CHCHaHb); 2.85 (d of d, 1H, 5-H); 2.27 (d of d, 1H, 5-H); 2.11 (s, 3H, 3-CH3).

1. customwas elevated up to 100° C
2. temperaturethe pH was maintained at 7.0 to 7.3
3. temperatureAfter cooling
4. extractionthe resultant mixture was extracted with ether (120 ml) 4 times
5. dry with materialdried over anhydrous magnesium sulfate
6. concentrationconcentrated at 40° C. under reduced pressure
7. customto give an oily substance (2.7 g)
8. customThe oily substance was chromatographed with silica gel (30 g)
9. additionfollowed by development with a solvent mixture of ethyl acetate and hexane (1:2 by volume)