Boron trifluoride etherate → 3-(1,2-Diphenylethyl)4-hydroxycoumarin

Participants

Reaction Steps

To a flame-dried flask containing a near-solution of 810 mg of 4-hydroxycoumarin and 1.20 mg of 1,2-diphenylethanol of Preparation 15 in 30 mL of dioxane under an argon atmosphere is added 3.0 mL of boron trifluoride etherate. The resulting yellow solution is left to stir at room temperature overnight; the reaction is then heated to reflux for 48 hours. The volatiles are removed and the residue is partioned between diethyl ether and 1N sodium hydroxide. The basic aqueous phase is washed with diethyl ether and acidified to pH=1 with 6N hydrochloric acid. The resulting precipitant is repeatedly extracted with dichloromethane (methanol-chloroform co-solvents). The combined dichloromethane extracts are washed once with dilute sodium bicarbonate to remove most of the unreacted 4-hydroxycoumarin, then brine, dried (magnesium sulfate), and finally concentrated under reduced pressure. The residue is adsorbed onto silica and flash column chromatographed with 40% to 50% ethyl acetate in hexanes to yield 167 mg of the title product as a white solid.

Provenance & Evidence