Br[CH2:2][C:3]([C:5]1[CH:10]=[CH:9][C:8]([Br:11])=[C:7]([Cl:12])[CH:6]=1)=[O:4].ClCC(C1C=CC(Br)=C(Cl)C=1)=O.[BH4-].[Na+].C[O-].[Na+]>C(O)C.CC(OC)(C)C>[Br:11][C:8]1[CH:9]=[CH:10][C:5]([CH:3]2[CH2:2][O:4]2)=[CH:6][C:7]=1[Cl:12]
To a stirred solution of the mixture of 2-bromo-1-(4-bromo-3-chlorophenyl)ethanone and 2-chloro-1-(4-bromo-3-chlorophenyl)ethanone (18.4 g) in ethanol (200 ml) at 5° C. was added portionwise over 5 min NaBH4 (2.23 g). The reaction mixture was then stirred at room temperature for 90 min to afford a yellow solution. TLC analysis showed the reaction was complete. Sodium methoxide (1.59 g) was then added and the reaction mixture was stirred at 50° C. for 4 h. TLC analysis showed the reaction was complete. The reaction mixture was then poured into TBME and washed with saturated brine. The organic layer was separated, then dried over Na2SO4 and concentrated in vacuo to afford (RS)-2-(4-bromo-3-chloro-phenyl)-oxirane (15.2 g) as a brown oil which was used in the next step without further purification.
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