Hydrochloric Acid → 1,3-Dihydroisobenzofuran

Participants

Reaction Steps

Lithium aluminum hydride (3.0 g) and 100 ml of dry tetrahydrofuran wereplaced in a 3-neck flask equipped with a mechanical stirrer, condenser witha nitrogen inlet and addition funnel. Phenolphthalein (6.4 g) dissolved in 300 ml of dry tetrahydrofuran was added dropwise to the stirred lithium aluminum hydride suspension at a rate to maintain a gentle reflux. When addition was complete, the reaction mixture was stirred for six hours at reflux by heating with an oil bath and then allowed to stand overnight. Tothe stirred solution was added excess ethyl acetate followed by 500 ml of water. The pH was adjusted to approximately 2 with conc. HCl and the solution extracted with two 500 ml portions of ether. The ether layer was washed six times with 10% aqueous potassium carbonate (each time the base layer was magenta), and then evaporated to dryness to leave an off-white solid (4.5 g crude yield). The solid was crystallized from 440 ml of 20% ethanol and dried in vacuo at 60° C. to give the corresponding phthalan as very light yellow crystals (yield 3.3 g; melting range 195°-197.5° C.). TLC using ether-silica gel gave one spot. Nmr did not show methine H and was more consistent with the cyclic ether (phenolphthalan) than the open form (phenolphthalol).

Provenance & Evidence