Phosphonite esters

A kinetic study of the previously reported substitution of aromatic nitro groups by tervalent phosphorus has established an aromatic 5n2 mechanism. Similarities in values of activation energies, and in relative reactivities of phosphite and phosphonite esters, between this displacement and the Arbusov reaction suggest a related mechanism (31), while the lack of reactivity of p-dinitrobenzene is attributed to the need for intramolecular solvation (32). The exclusive formation of ethyl nitrite, rather than other isomers, is confirmed from the decomposition of triethoxy-(ethyl)phosphonium fluoroborate (33) in the presence of silver nitrite. A mechanism involving quinquevalent phosphorus (34) still seems applicable, particularly in view of the recent mechanistic work on the Arbusov reaction. ... 

Schwetlick, K. Mechanisms of antioxidant action of phosphite and phosphonite esters. In Mechanisms of Polymer Degradation and Stabilisation Scott, G., Ed. Elsevier Science New York, 1990 23-60. 

The use of acyclic phosphonite esters, R P(OR)2, to prepare esters of phosphinic acids, R R P(0)0R (R and R may, or may not, be identical) is not so widely exemplified, but it may again be noted that there are always two routes, theoretically, to a target compound, as for example, in the case of the l,4-phenylenebis(methylene)bisphosphinic esters... 

It has already been indicated that the course of any reaction may depend, to some extent, on the nature of the phosphite (or phosphonite) ester (phosphinite esters yield phosphine oxides). Thus, tris(perfluoroalkyl) phosphites do not undergo a Michaelis-Arbuzov reaction with perfluoroiodoalkanes, although reports on the outcome of any reaction between triethyl phosphite and CF3I, under normal conditions, are conflicting reactions do appear to proceed under photostimulation. A normal reaction does take place at high temperatures between polyfluorinated trialkyl phosphites and methyl iodide, when the product, MeP(0)(0Rf)2, is accompanied by oxidation of the phosphite to phosphate Either elimination or alkylation accompanies the formation of unidentified phosphorus-containing products in the reactions between trialkyl phosphites and the halides Cl3C(CF2) Cl n - 2, 4 or 6) ... 

Several examples are known which demonstrate the greater reactivity of chlorine vs fluorine in unsaturated compounds in their behaviour towards phosphorus(III) esters. Thus, the interaction of 2,3-dichlorotetrafluoropropene and trimethyl phosphite proceeds through an allylic displacement, by either an ionic or a concerted mechanism (Scheme 1) to give the phosphonate 36 The 1,2-dichloroperfluorocycloalkenes 37 (/i = 2,3 or 4) also react with phosphite or phosphonite esters to give the phosphonates 38 or phosphinates... 

As already mentioned, phosphonous esters, RP(OR )2, are extremely reactive to propenoic and 2-methylpropenoic acids, and the products have the structure 446 (R = H or Reactions have also been performed with silyl phosphonite esters (447 R =... 

Equation 28 represents the formation of oxoalkyl phosphonic acid esters (488 R = OR) or phosphinic esters (488 R = alkyl or aryl) from phosphite or phosphonite esters and appropriate halogen-containing ketones ( > 1) or acyl halides (n = 0), and supplements the formation of the phosphonoylated or phosphinoylated alkanoic acids through reactions 21 and 22 in the previous section. 

Reactions between haloketones and phosphonite esters, R P(OR)2, produce enol esters of phosphonic acids or esters of the phosphinic acids, R (R C0CH2)P(0)0R, depending on the halogen involved whilst phosphinite esters, R2POR yield the phosphinic acid esters R2P(0)0CPh=CHBr when treated with a,a-dibromoacetophenone . ... 

The value of the phosphonite ester 386 in the synthesis of (aminoalkyl)phosphinic acids has been explored. This ester adds to nitroalkenes, acetylaminoalkenes, cyanoalkenes... 

Amirumethylation methods-Tha.t of phosphonite esters has provided polyaza... 

Of special interest is the double sandwich Co cyclopentadienyl derivative (8.219e), which can be made from a phosphonite ester by reaction (8.220). The Co" analogue, (tr-CjHj) C03 P(0)(0R)2 J X is also known. Some halogen derivatives can be made by direct modification of ligands (8.221). 

Phosphite and phosphonite esters act as antioxidants by three basic mechanisms depending on their structure (1). Basically, phosphites and phosphonites are secondary antioxidants that decompose hydroperoxides. Their performance in hydroperoxide decomposition decreases from phosphonites, alkyl phosphites, aryl phosphites, down to hindered aryl phosphites. Five membered cyclic phosphites act catalytically by the formation of acidic hydrogen phosphates. In contrast, hindered aryl phosphites are interrupting the branched kinetic chain. 

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