Phosphonous Acid and its Derivatives

Two preparations of diesters of phosphonous acid have been reported, - One of these, which claims to be the first preparation of these derivatives, involves the reaction of ammonium hypophosphite with triaikylsilylamines to give bis(trialkylsilyl) esters (127) in excellent yield. These compounds are extremely reactive, e.g. they are spontaneously inflammable in air. Dialkyl phosphonites (128) have also been prepared by the reduction of 

Phenylphosphinic anhydride (129) decomposes on heating to give phenylphosphine, phenylphosphonic acid (130), and pentaphenylcyclo-pentaphosphine. Phenylphosphinidene (PhP = ) has been shown to be an intermediate in this decomposition, by trapping with benzil to give the adduct (131) in very low yield. The phenylphosphine is suggested to be formed by a complex ionic reaction between pentaphenylcyclopentaphos- 

Paulsen, J. Thiem, and M. Moner, Tetrahedron Letters, 1971, 2105 H. Paulsen, W. Greve, and H. Kulme, ibid., p. 2109. 

The kinetics of the oxidation of phenylphosphonous acid (132) to phenylphosphonic acid by chromic oxide have been investigated. The reaction, which is first order in Cr, is catalysed by both acid and pyridine and the mechanism suggested involves the initial formation of a complex between chromic acid and the tervalent form of the starting acid. Ratedetermining decomposition of this complex is followed by rapid oxidation by Cr.  

In accord with the current interest in stereochemistry at phosphorus a number of optical studies on phosphonous derivatives have been carried out. Benschop and his group have achieved a partial resolution of alkyl alkylphosphinates (133) by stereospecific inclusion in cycloamyloses. Optical purities in the range 20—80% were obtained. 

---

Phosphonic acid and its derivatives Various alcohols and diacids 40,166... 

---