Intramolecular Phosphinyl‐Zincation of Alkynes: A Powerful Entry to Benzophosphole Oxides

Abstract Upon reacting ortho ‐alkynylated secondary arylphosphine oxides with Et 2 Zn, we discovered that P(O)─H activation is followed upon gentle heating by phosphinyl‐zincation. This unprecedented transformation stands as a phosphorus version of the silyl and germyl‐zincation of alkynes recently shown to give modular access to elaborated tri and tetra‐substituted alkenes. The cyclic vinyl‐zinc derivative resulting from intramolecular phosphinyl‐zincation was characterized by multi‐nuclear NMR spectroscopy. It subsequently undergoes Cu or Pd‐catalyzed derivatizations with a broad range of electrophiles. The synthetic utility of this one‐pot‐two‐step process has been leveraged to prepare a wide range of benzophosphole oxides (BPO) with diverse substitution patterns. Furthermore, π‐extended BPOs have been synthesized by C─C coupling or cyclization of C3‐alkynyl / alkenyl substituted compounds and their optical properties have been analyzed.