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

Participants

Reaction Steps

A mixture of 25.0 g (0.103 mole) 2-hydroxy-5-benzyloxyacetophenone, 8 mL (6.0 g, 0.130 mole) acetone and 4 mL (3.7 g, 0.052 mole) pyrrolidine in 100 mL toluene was stirred at room temperature for 4 hours, then refluxed over a Dean-Stark trap for 3 hours. An additional 8 mL (6.0 g, 0.130 mole) acetone and 4 mL (3.7 g, 0.052 mole) pyrrolidine was added and the mixture refluxed for 18 hours. The mixture was concentrated, poured into water, basified to pH 8 with ammonium hydroxide, then extracted with ether. The ether extract was washed successively with 1N KOH, 1N HCl, water and brine, then dried (MgSO4) and concentrated to give an oil. Flash chromatography on silica gel eluting with 20% ethyl acetate in hexanes afforded a solid. Recrystallization from ethyl acetate in hexanes afforded a solid. Recrystallization from ethyl acetate in hexanes yielded the title product as a solid 13.6 g (47%), mp 105°-107° C. NMR (CDCl3): δ1.4 (s, 6H); 2.7 (s, 2H); 5.1 (s, 2H).

Provenance & Evidence