Preliminary stereochemical investigation of the Atherton-Todd-type reaction between valine hydrospirophosphorane and phenols

The Atherton-Todd-type reaction of pentacoordinate hydrospirophosphoranes synthesized from l-valine with phenols was first investigated. A series of new types of phenoxy spirophosphoranes were stereospecifically synthesized and a preliminary stereochemical mechanism was proposed by 31P NMR tracing experiments and X-ray diffraction analysis. The reaction proceeded via the initial generation of chlorinated spirophosphorane intermediate with retention of the configuration at phosphorus, followed by the rear attack of nucleophilic substitution with phenols to produce phenoxy spirophosphoranes with stereoinversion of the phosphorus chiral center.