The synthesis and pseudorotations of spirophosphoranes.

A review of phosphorane chemistry is presented. From a range of spirophosphoranes the relative apicophilicity of sulphur and oxygen containing ligands was determined. The conclusion reached was that the relative apicophilicities of ethylthio, ethoxy and trimethylsiloxy were similar. The N-chlorodi-isopropylamine method for the preparation of spirophosphoranes was developed, enabling the preparation of various unsymmetrical phosphoranes, from which the relative apicophilicities of phenoxy and phenylthio groups were determined. The preparation of spirophosphoranes from phosphetans was shown to go with retention of configuration at phosphorus. The interconversion of the cis and trans spirophosphoranes prepared from phenyl and benzylphosphetans was followed kinetically, and from this study the phenyl group was shown to be more apicophilic than the benzyl group. Cyclic and acyclic phosphites were reacted with acrylic acid. In the case of cyclic phosphites spirophosphoranes were prepared from which the relative apicophilicity of the phenyl group was determined. A series of spirophosphoranes was prepared containing a 4,4,5,5-tetramethyl-1,3,2-dioxaphospholan ring. On thermolysis these were found to give 2,3-dimethyl-butadiene as the major component and some t-butyl methyl ketone. From a series of hexafluorobiacetyl and tetrachloro-o-benzoquinone adducts the relative apicophilicities of chlorine, cyanide, isocyanate and isothiocyanate were determined. It was shown that the cyanide was more apicophilic than chlorine, whilst the isocyanate and isothiocyanate were found to have a similar apicophilicity to chlorine. The first pentaco-ordinate phosphorane containing an azide ligand was prepared by direct substitution of a chlorospirophosphorane. From this spirophosphorane the relative apicophilicity of the azide group was determined; it was found to be slightly more apicophilic than the phenoxy group. By a similar procedure a spirophosphorane containing a cyanide ligand was prepared.