O-Xylene → 7-(phenylmethoxy)-8-(2-propenyl)-4H-1-benzopyran-4-one

Participants

Reaction Steps

A mixture of 5.0 g (17.73 mmol) of 1-[2-hydroxy-4-(phenylmethoxy)-3-(2-propenyl)phenyl]ethanone, 2.3 g (19.48 mmol) of dimethylformamide dimethyl acetal, and 5.0 mL of xylene was stirred and heated in a 120°-130° C. oil-bath as methanol was distilled out using a 3 in. Vigreux column, over a 2.5 hr period. The bath temperature was then raised to 150°-160° C. and the reaction mixture was stirred at this temperature for an additional 30 min. The mixture was cooled and concentrated at 60° C./high vacuum. To the viscous, red-brown, oily residue was added 3.7 g (19.48 mmol) of p-toluenesulfonic acid monohydrate and 50 mL of ethanol. The resulting solution was stirred and refluxed for 24 hr, then cooled and diluted with water. Work-up with ether in the usual manner gave a crude product which was recrystallized from hexane-ethyl acetate. There was obtained 3.5 g (67.6%) of 7-(phenylmethoxy)-8-(2-propenyl)-4H-1-benzopyran-4-one as a yellow solid, mp 90°-92° C.

Provenance & Evidence