Under a static nitrogen atmosphere at 0° C., a solution of n-butyllithium (3.94 g, 0.0615 mol) in hexane was added to a solution of tetramethylethylenediamine (1.86 g, 0.016 mol) in 30 ml. of anhydrous cyclohexane with constant stirring. While maintaining the temperature of the reaction at 0° C., a solution of N-benzylaniline (5.5 g, 0.03 mol) in 30 ml. of anhydrous cyclohexane was added to the reaction mixture to produce a suspension containing a dilithio compound which was stirred for an additional 2 hours at 26° C. 4-Phenylphenylphosphonic dichloride (8.7 g, 0.032 mol) was directly added to this suspension followed by 60 ml. of cyclohexane. The resulting mixture was stirred for 16 hours at 26° C. The reaction was quenched with the rapid addition of a solution of acetic acid (6 g, mol) in 30 ml. of anhydrous cyclohexane. After stirring for 30 minutes, the cyclohexane layer was removed under vacuum and the resulting residue was partitioned in methylene chloride and water. The layers were separated and the methylene chloride layer was washed with water, dried over sodium sulfate and concentrated in vacuo to yield an oily residue. The oily residue was chromatographically separated on a silica gel column using ethyl acetate as the eluant. Fractions containing the benzazaphosphole were combined and concentrated in vacuo to produce a crude product. The crude product was slurried in anhydrous diethyl ether to yield 1-(4-phenylphenyl)-2-phenyl-2,3-dihydro-1H-2,1-benzazaphosphole-1-oxide (0.55 g, 5% yield) as a white solid having a melting point of 259°-261° C. and the following analysis:
