Benzyl Bromide → (1R,2r)-benzyl2-methylcyclopropanecarboxylate

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Reaction Conditions

Reaction Steps

A mixture of 2-methylcyclopropanecarboxylic acid (commercial product which is a cis-trans mixture, 75.0 g, 0.75 mol) and 1 N NaOH (900 mL, 0.90 mol) is warmed and stirred at 45° C. To the stirring solution is added benzyl bromide (131.0 mL, 1.10 mol) and methyltrialkyl(C8-C10)ammonium chloride (Adogen™ 464, 37.5 g). The mixture is stirred at 40-45° C. for 4 h, cooled to room temperature, and extracted with ethyl ether (800 mL). The organic layer is dried (MgSO4) and evaporated to a liquid. Chromatography over silica gel, eluting with hexanes gradually increasing to 5% ethyl acetate in hexanes, provides the racemic benzyl trans-2-methylcyclopropanecarboxylate as a liquid (132.2 g, 93%); 1H NMR (DMSO-d6) δ 7.40 (m, 5H), 5.05 (s, 2H), 1.43 (m, 1H), 1.30 (m, 1H), 1.06 (d, J=6.0 Hz, 3H), 1.02 (m, 2H), 0.74 (m, 1H). [Note: If NMR reveals the presence of a minor amount of cis isomer, it is removable by the chiral HPLC separation which may be carried out as described above.]

Provenance & Evidence