Boron tribromide → 1-(4-(3-Chloropropoxy)-3-hydroxyphenyl]ethanone

Participants

Reaction Steps

To a stirred solution of 1-[4-(3-chloropropoxy)-3-methoxyphenyl]ethanone (10.0 g, 41 mmol) in methylene chloride (120 ml) cooled to -50° C. (dry ice-methanol) was added, dropwise, 1 M boron tribromide in methylene chloride (123 ml, 120 mmol). The temperature was kept between -40° C. and -50° C. After complete addition, the reaction was permitted to reach -30° C., and the TLC checked (ca. 15 min. after final boron tribromide was added). Saturated NaHCO3 was added, dropwise, never allowing the temperature to go above 0° C. during most of the addition. When sufficient NaHCO3 had been added to make the solution basic, the organic layer was; collected. The layer was washed with brine, dried (MgSO4), and concentrated to yield 8.1 g of dark brown oil, which solidified on standing. This was chromatographed on a Waters Prep 500 LC (2 silica columns, 2% methanol-methylene chloride as eluent). Upon concentration of the appropriate fractions, 5.8 g of a brown tacky solid were obtained. This was recrystallized from isopropyl ether (with decanting of the yellow isopropyl ether supernatant from the dark brown oily residue) to give initially 2.5 g; of a yellow solid. Concentration of the mother liquor gave an additional 0.5 g, m.p.=110-113° C.

Provenance & Evidence