Generation and Reactions of Transient Nitrilium Phosphane Ylide Complexes

Abstract

Thermal decomposition of a 2H-azaphosphirene tungsten complex in the presence of N-piperidino nitrile and various trapping reagents (different nitriles, a ketone and an alkyne) yielded five-membered heterocycles, that are coordinated to pentacarbonyltungsten. These reactions are described as 1,3-dipolar cycloadditions of in situ generated nitrilium phosphane ylide complexes with the π-electron systems of the latter trapping reagents. The regioselectivity of this 1,3-dipol system is directed by the substituent attached to the dicoordinated carbon atom e.g. with phenyl the regioselectivity of such intermediates is nitrile sulfides-like, whereas with the N-piperidino substituent an Umpolung is achieved and it becomes nitrile ylides-like.

Keywords::

• nitrilium phosphane ylide complexes
• phosphorus heterocycles
• 1,3-dipolar cycloaddition reactions
• N-ligands
• P-ligands