反应详情

Into a reaction vessel, a solution of 4-hydroxy-4-methyl-5-propargyl-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 6.8 with 0.1 N NaOH solution, and stirring was continued at 100° C. for 4 hours, during which the pH was maintained at 6.8 to 7.0. After cooling, NaCl (40 g) was added to the reaction mixture and 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 (2.5 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-propargyl-3-methyl-4-hydroxy-2-cyclopentenone (2.3 g). Yield, 77%. N.M.R. (CDCl3, internal standard TMS, δ ppm, 90 MHz): 4.60 (broad d, 1H, 4-H); 3.95 (broad s, 1H, 4-OH); 3.04 (d, 2H, --CH2 --C≡H); 2.65 (d of d, 1H, 5-H); 2.38 (d of d, 1H, 5 -H); 2.20 (s, 3H, 3-CH3); 1.98 (s, 1H, C≡CH).

1. customwas elevated up to 100° C
2. temperaturethe pH was maintained at 6.8 to 7.0
3. temperatureAfter cooling
4. extractionextracted 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 (2.5 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)