反应详情

A solution of 2-hydroxypropiophenone (500 ml, 3.64 mol), acetone (400 ml), and pyrrolidine (150 ml, 1.8 mol) in toluene (1000 ml) was heated at 85° C. for 66 hours. The cooled solution was then washed successively with water, aqueous hydrochloric acid and aqueous sodium hydroxide solution. The toluene layer was separated and the solvent removed under reduced pressure. The residue was chromatographed on silica gel, eluting with dichloromethane/heptane (50/50), to give 81 g of 2,2,3-trimethyl-3,4-dihydro-2H-1-benzopyran-4-one as an oil, a compound of Formula (3a); 1H NMR (CDCl3): δ1.3 (d,3H), 1.4 (s,3H), 1.6 (s,3H), 2.5-3.0 (q,1H), 6.8-8.1 (m,4H).

1. washThe cooled solution was then washed successively with water, aqueous hydrochloric acid and aqueous sodium hydroxide solution
2. customThe toluene layer was separated
3. customthe solvent removed under reduced pressure
4. customThe residue was chromatographed on silica gel
5. washeluting with dichloromethane/heptane (50/50)