“…Moreover, compounds 56 and 57 do add to each other to give the final product 55, which has been proved in a model reaction. 77,82 Scheme 3 is also consistent with increase in the reaction rate with the increase in the electron-donor ability of the substituents at the phosphorus atom. Finally, which is also proved by kinetic studies, 78 hydrogen chloride, which is always present in the reaction mixture, plays an important role in these reactions.…”