4-Bromotoluene → 4'-Methyl-2-nitro-1,1'-biphenyl

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Reaction Conditions

Reaction Steps

A 1 L three-necked 24/40 round-bottom flask equipped with a mechanical stirrer, a 250 mL constant pressure addition funnel with a nitrogen inlet at the top, and a septum was flame dried, cooled and then charged with a solution of 29.07 g (0.17 mol) of p-bromotoluene in 100 mL of anhydrous tetrahydrofuran under a nitrogen atmosphere. The solution was stirred and cooled to -78° C. and 200 mL (0.34 mol) of a 1.7M solution of t-butyllithium in pentane was added via the addition funnel over 30 minutes. When the addition was complete, the cooling bath was removed and the reaction mixture was stirred for 30 minutes and allowed to warm to room temperature. The dropping funnel was next charged with 170 mL (0.17 mol) of a 1.0M solution of zinc chloride in diethylether which was added to the reaction mixture over a 10 minute period. A separate 1 L three-necked 24/40 round-bottom flask equipped with a mechanical stirrer, a nitrogen inlet and a septum, was flame dried, cooled and then charged with 4.04 g (6.0 mmol) of bis(triphenylphosphine)palladium(II) chloride and 50 mL of anhydrous tetrahydrofuran under a nitrogen atmosphere. The stirrer was started and 8.0 mL of a 1.5M solution (12 mmol) of diisobutylaluminum hydride in toluene was added to the suspension via syringe. The catalyst was stirred an additional 10 minutes at room temperature, and then a solution of 23.23 g (0.115 mol) of 1-bromo-2-nitrobenzene in 100 mL of anhydrous tetrahydrofuran was added. The suspension of the tolylzinc chloride was then transferred to the second flask via a wide diameter cannula. The reaction mixture was stirred an additional 45 minutes at room temperature, then most of the tetrahydrofuran was removed on a rotary evaporator. The resulting oil was partitioned between ethyl acetate and 1.0N hydrochloric acid. The organic layer was washed successively with water and brine, then dried (MgSO4), filtered and evaporated. The residual oil was purified on a silica gel flash chromatography column eluted with 10% ethyl acetate-hexane to afford after evaporation and drying in vacuo 15.43 g (63%) of the product as a viscous yellow oil:

Provenance & Evidence