π-Insertion Reactions of Benzynes into P=N and P=S Double Bonds

The π‐insertion reactions of in situ generated benzynes into the P=N bonds of N‐benzyl and N‐aryl iminophosphoranes and the P=S bonds of phosphane sulfides have been examined by using the Kobayashi benzyne precursors, (2‐trimethylsilyl)phenyl triflates. The reactions with iminophosphoranes afforded (2‐aminophenyl)phosphonium triflates under mild conditions, most probably by a [2+2]/retro [2+2] cycloaddition sequence and further N‐protonation by the solvent (CH3CN) or N‐phenylation by a second molecule of benzyne. The final products of the analogous reactions with P‐OCH3‐substituted iminophosphoranes were the respective (2‐aminophenyl)phosphane oxides, as result of a final O‐demethylation event of the putative phosphonium triflate. The reactions with phosphane sulfides involve a final S‐phenylation step to yield (2‐phenylthio)phenylphosphonium salts. P‐Phenylphosphonium triflates functionalized at the ortho position by amino or thio units were obtained by π‐insertion of benzyne into the P=N bond of an iminophosphorane or the P=S bond of a phosphane sulfide.