Hydrochloric Acid → ethyl p-[2-(3,4-dihydro-4,4-dimethyl-2H-1-benzopyran-7-yl)propenyl]benzoate

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Reaction Conditions

Reaction Steps

0.5 g of a 50% suspension of sodium hydride in mineral oil were suspended in 15 ml of dimethyl sulfoxide and treated under argon with a solution of 3.2 g of diethyl (4-carbethoxybenzyl)phosphonate in 10 ml of dimethyl sulfoxide. The mixture was subsequently heated to 40° C. for 20 minutes, cooled to room temperature, a solution of 0.87 g of 3,4-dihydro-4,4-dimethyl-7-acetyl-2H-1-benzopyran in 5 ml of dimethyl sulfoxide was added dropwise thereto and the mixture was heated to 40° C. for 1 hour. The reaction mixture obtained was poured on to ice/water, acidified with 1N hydrochloric acid and extracted repeatedly with ether. The organic phase was washed with water, dried and evaporated. There was obtained a yellowish oil which, after filtration over a short column (silica gel, eluting agent hexane/ethyl acetate=9:1), crystallized from hexane and yielded 0.9 g of ethyl p-[2-(3,4-dihydro-4,4-dimethyl-2H-1-benzopyran-7-yl)propenyl]-benzoate, m.p. 48°-50° C.

Provenance & Evidence