A phosphoryl to spiro-bicyclophosphorane transformation via β-amidic proton elimination in phosphorylated hydrazides

The reaction between phosphoryl-containing reagents and hydrazides has been studied. The tetrahedral phosphoryl structure is transformed into a spiro-bicyclophosphorane system with trigonal bipyramidal geometry by the elimination of a β-amidic proton in the reaction between a hydrazide and phosphoryl reagents with at least two leaving groups (Cl) bound to the phosphorus atom, such as POCl3 or PhPOCl2. In the spiro-bicyclophosphorane structure, the CN imine bond is formed upon β-amidic proton elimination, leading to the conversion of the CO into a C–O bond and the formation of a P–O bond. All of these structural rearrangements are supported by X-ray crystallography data, and NMR and IR experiments.