2,4-Bis(4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane → Ethyl 2-phenyl-4-thioxo-4H-1-benzopyran-8-carboxylate

Participants

Reaction Steps

A solution of 4.0g of 8-ethoxycarbonyl-2-phenyl-4-oxo-4H-1-benzopyran (prepared as described in Da Re et al., Ber. 1962, 99 (1966)) and 3.55 g of 2,4-bis-(4-methoxyphenyl)-1,3-dithia-2,4-diphosphetane (Lawesson's reagent) in 68 ml of toluene was stirred at reflux for 2 hours. The reaction mixture was cooled to room temperature and evaporated to dryness in vacuo. The crude residue was rinsed with petroleum ether and filtered to give a solid. The material was purified by flash chromatography on silica gel, eluting with a petroleum ether - ethyl acetate gradient (9:1 to 7:3). Evaporation in vacuo of the collected fractions yielded 3.99 g of pure title compound, melting at 161°-163° C. after recrystallization from cyclohexane.

Provenance & Evidence