Phosphine Oxides and Related Compounds

The major development of the year is that of phosphine oxide-based olefin synthesis into a really useful method complementing the Wittig reaction. 

Both sulphur trioxide and sulphuryl chloride fluoride oxidize phosphines (and triphenylarsine) to the corresponding oxides in excellent yields under mild conditions. The effect of various iron compounds as catalysts for the oxidation of phosphine to phosphine oxide have been investigated triphenylphosphine oxide is formed quantitatively at 30—70 °C in oxygen at one atmosphere. 

Various heptylbis-(5-substituted-2-thienyl)phosphine oxides (1) have been prepared by Friedel-Crafts reaction of heptylphosphoryl chloride with the 

A new route to optically active trialkylphosphine oxides, and hence phosphines, has been reported. The key step, the conversion of the optically active phos-phinite (4) to phosphine oxide, is extremely sensitive to the solvent mixture used, and even under the most favourable conditions involves considerable racemization. Small levels of optical activity (0—8 % enantiomeric excess) have been induced in the phosphine oxide product by hydrolysis of the phosphonium salt (5) under phase-transfer conditions using optically active quaternary ammonium salts as chiral catalysts.  

Another surprisingly stable compound containing a P=P bond has been isolated. Reaction of the sterically hindered arylphosphonic dichloride (6) with magnesium gives the crystalline diphosphene oxide (7), which, not surprisingly, is rapidly hydrolysed by water. The tris(diphenylthiophosphinoyl)meth-anide (8) has been isolated as its tetra-n-butylammonium salt.  

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The acyl phosphonates, acyl phosphine oxides and related compounds (e.g. 81. 82) absorb strongly in the near UV (350-400 nm) and generally decompose by rescission in a manner analogous to the benzoin derivatives.381"285 Quantum yields vary from 0.3 to 1.0 depending on structure. The phosphinyl radicals are highly reactive towards unsaturated substrates and appear to have a high specificity for addition v.v abstraction (see 3.4.3.2). 

This year s literature has been characterized by an increasing number of papers devoted to theoretical studies of the bonding in phosphine oxides and related compounds, and these are discussed in Section 1. The chemical aspects of phosphine oxides have not shown any major new developments over the past year, and, once again, these have been sub-divided into sections on the preparation and on the reactions of phosphine oxides. 

CHAPTER 3 Phosphine Oxides and Related Compounds By B.J. Walker... 

Chiariza, R., Horwitz, E.P. 1986. Hydrolytic and radiolytic degradation of octyl(phenyl) butyl carbamoylmethyl phosphine oxide and related compounds. Solvent Extr. Ion Exch. 4(4) 677-723. 

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