Highly Atom-Economic One-Pot Formation of Three Different C-P Bonds: General Synthesis of Acyclic Tertiary Phosphine Sulfides

The reaction of benzothiadiphosphole 1 with an equimolar mixture of R 1 MgBr and R 2 MgBr gave intermediate A¢, which, after only 4-5 min, was treated with an equimolar amount of R 3 MgBr, giving the asymmetric phosphine PR 1 R 2 R 3 in 45% overall yield (75-80% yield when R 1 ) R 2 and 85-90% yield when R 1 ) R 2 ) R 3 ) and the byproduct 6 in 90% yield. The treatment of 6 with PCl3 quantitatively regenerates the starting reagent 1. Treatment of the phosphines with elemental sulfur gave the corresponding sulfides