QUASIPHOSPHONIUM INTERMEDIATES .7. THE PREPARATION OF TRINORBORN-1-YL PHOSPHITE AND ITS REACTIONS WITH HALOGENO COMPOUNDS - STABLE INTERMEDIATES OF THE ARBUZOV AND PERKOW REACTIONS AND THEIR STRUCTURAL CHARACTERIZATION BY X-RAY-DIFFRACTION, NMR-SPECTROSCOPY, AND FAST-ATOM-BOMBARDMENT MASS-SPECTROMETRY

Trinorborn-1-yl phosphite has been prepared and has been shown to give highly stable phosphonium salts in its reactions with iodomethane and with a number of alpha-halogenoketones. Phenacyl bromide and p-bromophenacyl bromide underwent reaction at room temperature to give the corresponding ketophosphonium halides (Arbuzov intermediates) as the exclusive products, whilst p-nitrophenacyl chloride gave the corresponding vinyloxyphosphonium chloride (Perkow intermediate) as the first example of a stable intermediate of this type. The structures of these two types of intermediate in the solid state were confirmed by X-ray diffraction measurements which revealed distorted tetrahedral arrangements around phosphorus, with P+ ... Br- and P+ ... Cl- interionic distances of 4.58 and 4.71 angstrom for the phenacyl bromide and p-nitrophenacyl chloride adducts respectively. Phenacyl chloride, chloroacetone, and p-nitrophenacyl bromide gave mixed products, amongst which trinorborn-1-yl phosphate was always present. Possible reaction mechanisms are discussed. Thermal decomposition of the Arbuzov intermediates (149-degrees-C) gave the expected phosphonates but the Perkow intermediate underwent elimination of alkyne under these conditions to give trinorborn-1-yl phosphate. P-31 NMR and fast atom bombardment mass spectra of the quasiphosphonium salts are reported and discussed.