Triethylsilane → 2-(4-Ethylbenzyl)-4-bromo-1-chlorobenzene

Participants

Reaction Conditions

Reaction Steps

To a stirred solution of Et3SiH (400 g, 3.45 mol) and (5-bromo-2-chlorophenyl)(4-ethylphenyl)methanone (534 g, 1.65 mol) containing ˜7% of the isomeric ketone in 300 mL of the TFA at 30° C. was added CF3SO3H (1.5 g, 0.01 mol). Within minutes the temperature increased causing the solution to reflux violently. Caution: this moderate exotherm requires cooling with an external ice bath. After 1 hr, HPLC revealed the reaction to be 90% complete. After addition of an additional Et3SiH (20 g) and heating overnight at 70° C., the reaction was >95% complete by HPLC analysis. Upon cooling, the volatiles were removed by bulb to bulb distillation at reduced pressure. The resultant ˜1 L of the light gray oil was poured into 1 L of H2O. The mixture was extracted three times with hexane, the combined organic layers were washed three times with H2O, twice with aq Na2CO3 and twice with brine before drying over Na2SO4. After concentration using a rotary evaporator, ˜1 L of clear light amber oil remained. This material was further concentrated, the (Et3Si)2O (450 mL) was removed by distillation until the distillation head temperature reached 75° C., and the residue was allowed to cool. 1HNMR analysis of the residue revealed it to contain an ˜8:1 mixture of diarylmethane to (Et3Si)2O. Crystallization of this mixture was achieved by pouring the product into vigorously stirred cold (10° C.) mixture of 85% EtOH:H2O (1.2 L). After stirring for several hours, the crystals were collected by filtration, washed with cold 1:1 EtOH/H2O and dried under vacuum. The 4-bromo-1-chloro-2-(4-ethylbenzyl)benzene (500 g), was obtained as a low melting solid containing ˜1% (Et3Si)2O, and was used without further purification.

Provenance & Evidence