Unusual Reactivity of (Vinylimino)phosphoranes and Their Utility in the Preparation of Pyridine and Dihydropyridine Derivatives

New reactions of (vinylimino)phosphoranes with aldehydes involving an initial nucleophilic attack of the beta-carbon atom of the vinyl side chain on the carbonyl carbon atom are reported. Iminophosphorane 4 derived from ethyl beta-azidoacrylate reacts with substituted cinnamyl aldehydes to give a mixture of 2-arylpyridine and 4-styryldihydropyridine derivatives, whereas the reaction with substituted benzaldehydes provides 4-aryldihydropyridine derivatives. However, the iminophosphorane 16 derived from the diethyl azidofumarate reacts with cinnamyl aldehydes through the expected aza-Wittig fashion to give 4-arylpyridine derivatives after dehydrogenation of the resulting dihydropyridine.     

Polydentate phosphines

Phosphines are one of the most important classes of ligands in chemistry, in both the industrial and academic spheres. This review deals with the design and properties of polydentate phosphines, an original and broad class of multidentate ligands. The multidentate nature of these species has led to special properties, in which the spatial proximity of phosphorus atoms is crucial. The first part gives an overview of oligodentates polyphosphines in which is discussed the types and the basic routes for their synthesis. The review continues with the most important synthetic routes for obtaining complexes. Because of huge amount of literature data this review is not exhaustive, but it collects the most relevant findings in this area. The restriction to structural and spectroscopic properties allows us for a well organized handling of the complex material.     

A versatile synthesis of a new bisiminophosphorane

The iminophosphorane CH₂CH₂[P{NP(O)(OPh)₂}Ph₂]₂ is synthesized in high yields (80–97%) via a very convenient procedure using diphenylphosphoryl azide (DPPA) and 1,2-bis(diphenylphosphino)ethane.