Phosphorus pentachloride → Naphtho(2,3-b)thiophene-4,9-dione

Participants

Reaction Steps

2-(thiophene-2-carbonyl)benzoic acid (1, 14.0 g, 60.3 mmol, 1.0 equiv.), nitrobenzene (400 mL), and phosphorus pentachloride (18.8 g, 90.4 mmol. 1.5 equiv.) were added to a schlenk flask. Aluminum chloride was then added (12.1 g, 90.4 mmol, 1.5 equiv.), and the reaction was stirred for 1 hour at room temperature followed by 4 hours at 140° C. The solvent was distilled off under vacuum, and the black residue was sonicated in dichloromethane (500 mL) and filtered through CELITE®. The filtrate was concentrated in vacuo and purified by column chromatography (silica gel, dichloromethane:hexanes (1:1)→dichloromethane). The product was further purified by recrystallization from methanol to give 2 as brown needle-shaped crystals (6.45 g, 50%). 1H NMR (500 MHz, CDCl3) δ8.26-8.24 (m, 2H), 7.78-7.77 (m, 2H), 7.75-7.71 (m, 2H). m.p. 232-234° C.

Provenance & Evidence