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 (RMgBr)-Mg-1 and (RMgBr)-Mg-2 gave intermediate A', which, after only 4-5 min, was treated with an equimolar amount of (RMgBr)-Mg-3, giving the asymmetric phosphine (PRRR3)-R-1-R-2 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.