Stable [2+2]‐Cycloadducts of Ketones with Phosphazenes Having Five‐Membered Rings

Abstract

The formal analogy between the Wittig reaction and the addition of ketones to compounds having PN bonds includes the formation of an intermediate. The four‐membered ring compound (1) is isolable owing to stabilization by the σ5‐phosphorus atom.

Molecules that we made: An essay on phosphorus chemistry

“…The cycloadducts, such as 21, are five-membered cyclic phosphazenes that stay monomeric but which add almost any other unsaturated system to their P‫ס‬N bond. With ketones, we observed the occurrence of an aza-Wittig reaction, of which the intermediate 22 can be isolated [65,66]. We also obtained adducts with CO 2 and CS 2 [67], isocyanates [68], isothiocyanates [69], ketenes [70], iminophosphines and iminophosphoranes [71], epoxides [72], nitrones, nitrile oxides, and nitrile imines [73,74].…”