Acetone → 6-Hydroxy-2,2-dimethylchroman-4-one

Participants

Reaction Steps

To a 250 mL, 2-necked round bottom flask equipped with a magnetic stir bar and a water-jacketed condenser capped with a balloon was added 2′,5′-dihydroxyacetophenone (2, 8.00 g, 52.6 mmol), reagent grade acetone (19.45 mL, 263 mmol), piperidine (5.2 mL, 52.6 mmol) and freshly distilled pyridine (50 mL). The mixture was heated to a vigorous reflux with stirring under a nitrogen atmosphere for 2 d. The solvent was evaporated and the concentrate was dried under high vacuum. Reagent grade acetone (19.45 mL, 263 mmol), piperidine (5.2 mL, 52.6 mmol) and freshly distilled pyridine (50 mL) were added, and vigorous reflux with stirring under a nitrogen atmosphere was continued for 2d more. The solvent was evaporated, ethyl acetate (30 mL) and 30% aqueous CuSO4 (30 mL) were added to the concentrate. The organic phase was washed with brine (1×30 mL), dried over MgSO4, filtered, concentrated and dried under high vacuum. The dry crude product was passed through a silica gel column using 2:1 hexanes/ethyl acetate as eluent (Rf=0.3). The product gives off a purple color on an analytical silica gel plate illuminated with a short wave UV lamp. The fractions containing the pure product were transferred to a pre-weighed flask, the solvent was evaporated and the concentrate was dried under high vacuum. The reaction furnished 7.65 g of 3 (76%) as a brown solid. 1H NMR (300 MHZ, CDCl3): δ 7.32 (m, 1H), 7.04 (m, 1H), 6.82 (m, 1H), 5.48 (bs, 1H), 2.68 (s, 2H), 1.42 (s, 6H). 13C NMR (75.5 MHZ, CDCl3): δ 193.8, 154.4, 149.9, 125.2, 120.0, 119.6, 110.7, 79.0, 48.7, 26.5; HRMS (EI+): calculated for C11H12O3 [M+] m/z 192.0786, found 192.0788.

Provenance & Evidence