Carbazole → 9-(p-Tolyl)carbazole

Participants

Reaction Steps

Allylpalladium(II) chloride dimer ([PdCl(π-allyl)]2) (5.8 mg, 0.025 mol %) and di-tert-butyl(2,2-diphenyl-1-methyl-1-cyclopropyl)phosphine (cBRIDP) (22.2 mg, 0.1 mol %) were placed into a 50 mL, two-necked, round bottomed flask equipped a gas inlet, and the flask was evacuated and filled with nitrogen. Subsequently, to the mixture was added dehydrated THF (8.2 mL, 101.0 mmol, 1.6 equivalents), and the mixture was stirred at room temperature for 1 minute to prepare a THF solution of an equivalent mixture of PdCl(π-allyl)(cbridp) and cBRIDP (a catalyst solution) as a pale yellow liquid. Separately, a 200 mL, four-necked, round-bottomed flask equipped with a Teflon® coated magnetic stirring bar, condenser, dropping funnel, thermometer, and a gas inlet was evacuated and filled with nitrogen. Carbazole (10.9 g, 65.0 mmol, 1.03 equivalents) and dehydrated xylenes (66 mL) were charged into the flask, and the mixture was cooled to 5° C. using an ice bath. Subsequently, to the mixture was added a THF solution of methylmagnesium chloride (MeMgCl) (3.22 mol/L, 20.0 mL, 64.4 mmol, 1.02 equivalents) (containing THF in an amount of 17.3 mL (15.4 g, 213.6 mmol, 3.4 equivalents)) dropwise via the dropping funnel over 10 minutes at such a rate that the temperature of the reaction solution was kept at 20° C. or lower, and then the dropping funnel was washed with dehydrated xylenes (11 mL). Subsequently, to the solution were added 4-chlorotoluene (7.5 mL, 63.1 mmol, 1.0 equivalent) and the catalyst solution (8.2 mL) successively, and the solution was stirred for 1 hour under reflux. GC analysis at this point to check progress of the reaction reveals that 4-chlorotoluene (GC retention time: 2.8 minutes) has been completely consumed. After cooling the reaction mixture to room temperature, to the mixture were added water (25 mL) and ammonium chloride (1.7 g, 31.8 mmol, 0.5 equivalents). The aqueous layer was separated off, and the organic layer was concentrated under reduced pressure to give oily residue, which was purified by silica gel column chromatography (eluent: n-hexane/toluene=2/1) to afford 16.0 g of N-(4-methylphenyl)carbazole as a white powder.

Provenance & Evidence