反应详情

A solution of 2,5-dimethyl-4-hydroxy-3(2H)-furanone (pineapple ketone, 133.0 g, 1.0 mole) and triethylamine (152.0 g, 1.5 moles) in methylene chloride (665 g) is cooled to 5° C. under nitrogen atmosphere. To the cooled solution is added over a period of 2.5 hours, a solution of ethyl chloroformate (127.7 g, 1.18 moles) in methylene chloride (600 g) stirred at 5°-8° C. for two additional hours. The reaction mixture is filtered through a Buchner funnel to remove the triethylamine hydrochloride. The salt is washed with methylene chloride (200 ml). The combined organic layers are washed twice with 100 ml portions of water and dried over sodium sulfate. The solvent is removed in vacuo and the crude product distilled (<0.1 torr) through a Goodloe column to yield 72.5% of ethyl 2,5-dimethyl-3-oxo-4(2H)-furyl carbonate product b.p. 87° C. (0.08 torr), IR (neat film) 2980(M), 1770(S), 1715(S), 1640(S), 1250(S) cm-1, 'H NMR δ1.58 (t, J=8 Hz, 3), 1.65 (d, J=7 Hz, 3), 2.32 (s, 3), 4.45 (q, J=7 Hz, 2), 4.75 (q, J=7 Hz, 1), and 3.3% of the diadduct, diethyl 2,5-dimethyl-3,4-furyl dicarbonate, b.p. 110° C. (0.08 torr), IR (neat film 2980(M), 1770(S), 1250(S), 'H NMR δ=1.50 (t, J=6 Hz, 6) 2.3 (S, 6) 4.45 (q, J=8 Hz, 4).

1. additionTo the cooled solution is added over a period of 2.5 hours
2. filtrationThe reaction mixture is filtered through a Buchner funnel
3. customto remove the triethylamine hydrochloride
4. washThe salt is washed with methylene chloride (200 ml)
5. washThe combined organic layers are washed twice with 100 ml portions of water
6. dry with materialdried over sodium sulfate
7. customThe solvent is removed in vacuo
8. distillationthe crude product distilled (<0.1 torr) through a Goodloe column