Cyclic‐Phenoxaphosphinine‐Based Mixed Phosphonium‐Iodonium Ylides with Electron‐Withdrawing Substituents – Synthesis and Structural Features

Abstract

AbstractA series of phosphonium ylides and mixed phosphonium‐iodonium ylides based on cyclic phenoxaphosphinine has been synthesized, representing a new structural type of ylides. The influence of the electron‐withdrawing substituents of various nature on the stability and physicochemical properties of phenoxaphosphonium ylides is discussed. Our findings reveal a progressive reduction in ylide stability as the carbonyl group is replaced first with a phosphonate group and then with a nitrile group. NMR data indicates that the presence of a cyclic phosphonium group results in a lowered energy barrier to rotation about the carbon‐carbon bond, both in phosphonium and mixed phosphonium‐iodonium ylides with α‐carboxyl substituents when compared to triarylphosphonium ylides. These experimental results are further supported and analyzed in the context of density functional theory (DFT) calculations.