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

Beteiligte Stoffe

Reaktionsschritte

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, 1M 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.

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