反应详情

2,2-Dimethylchroman-4-one (4 g, 23.2 mmol) was added portionwise over 10 minutes to 7 ml of concentrated sulfuric acid at 0°-5° C., then cooled in an acetone-ice bath as concentrated nitric acid (s.g. 1.5, 90%, 1.4 ml) in 3 ml concentrated sulfuric acid was added dropwise over 20 minutes. The resulting mixture was poured into 100 ml ice and water and extracted 2×50 ml ethyl acetate. The organic layers were combined, washed 4×50 ml water and then brine, dried over magnesium sulfate, stripped to solids (5.3 g) and chromatographed on 500 g silica gel, gradiently eluting with 20:1, 15:1, 10:1 and finally 5:1 hexane:diethyl ether to yield title product as a white solid, 2.1 g (39%); tlc Rf 0.3 (1:1 diethyl ether:hexane); m/e 221(P+), 206, 166, 120.

1. additionwas added dropwise over 20 minutes
2. extractionextracted 2×50 ml ethyl acetate
3. washwashed 4×50 ml water
4. dry with materialbrine, dried over magnesium sulfate
5. customchromatographed on 500 g silica gel
6. washgradiently eluting with 20:1, 15:1, 10:1 and finally 5:1 hexane