Phosphonites

Other chiral monophosphonito-systems, e.g. (63) have also been prepared, and their role in catalysis explored. The vinylphosphonite (64) has been shown to suffer cleavage of the phosphorus-carbon bond in protic solvent systems containing potassium carbonate. 

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Secondary phosphines are likewise intermediates in the syntheses of phosphonites. The primary and secondary phosphines can also be used to make other mixed phosphines. 

Manufacture. Trichloromethanesulfenyl chloride is made commercially by chlorination of carbon disulfide with the careful exclusion of iron or other metals, which cataly2e the chlorinolysis of the C—S bond to produce carbon tetrachloride. Various catalysts, notably iodine and activated carbon, are effective. The product is purified by fractional distillation to a minimum purity of 95%. Continuous processes have been described wherein carbon disulfide chlorination takes place on a granular charcoal column (59,60). A series of patents describes means for yield improvement by chlorination in the presence of dihinctional carbonyl compounds, phosphonates, phosphonites, phosphites, phosphates, or lead acetate (61). 

Dialkyl esters of 3,3 -thiodipropionic acid (53), cycHc phosphonites such as neopentylphenyl phosphite, derivatives of phosphaphenathrene-lO-oxide (54), secondary aromatic amines, eg, diphenylamine (55), and epoxidi2ed soybean oils (56) are effective stabili2ers for preventing discoloration of cellulose esters during thermal processing. 

Saegusa et al. succeeded in preparing alternating oligomers from ethylene phenyl-phosphonite, acrylic monomer and carbon dioxide through zwitter ions280. ... 

Propanesultone also forms random and alternating copolymers with N-substituted ethylenimines276) and similar mechanisms involving zwitter ions were suggested. The polymerization through zwitter ions was performed with cyclic phosphonite as the Mn monomer and pyruvic acid as the ME monomer250). 

The formation of the phosphoranes (23) in the preparation of the phosphonites (24) has been shownto be due to two processes firstly, the acid-catalysed disproportionation of the phosphonites to give (23) and cyclopolyphosphines and secondly, the remarkable base-catalysed reaction of the phosphonites with catechol to give (23) and hydrogen. 

The mechanism of the Arbusov reaction has been the subject of some study. Intermediates (4), isolated at low temperatures from the reaction of phosphonites with alkyl halides, show n.m.r. chemical shifts in the region of — 95 p.p.m. in a wide variety of solvents. ... 

An earlier report that diethyl t-butylphosphonite (10) did not undergo an Arbusov reaction, presumably for steric reasons, has been withdrawn since the presumed phosphonite is now shown to be the phosphonate. 

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. ... 

D. Cyclic Esters of Phosphorous Acid.—There has been some controversy about the stable stereochemistry at phosphorus in cyclic phosphites and phosphonites this now appears to be resolved by agreement in a series of papers. The stereochemistry of 2-alkoxy-4-methyl-l,3,2-dioxaphosphorins... 

In an attempt to isolate the anomeric effects, analogous phosphonites have been studied. Equilibration of cis- (109) and /ra 5-2-methyl-5-t-butyl-l,3,2-dioxaphosphorinanes(l 10) demonstrated the thermodynamic preference for cis over trans (72% and 28% respectively at 40 °C). This surprising result must mean that axial P-methyl is more stable than equatorial even when no anomeric effects are present, and the authors interpret their n.m.r. results in terms of two equilibrating conformers for trans- 10)... 

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... 

Hydrolysis products With an excess of water by weight, QL form 2-diisopropylaminoethanol, ethanol, and methyl phosphorous acid. With traces of water or other proton donors QL will produce diethylmethyl phosphonite and 0,0 -bis-(2-diisopropylaminoethyl) methylphosphonite. Diethylmethyl phosphonite has a boiling point of 120°C and a vapor pressure of 11 mmHg at 20°C and is highly flammable. 

As to Irgafos 168 the reader is advised to notice the results of a round-robin involving PP/(Irganox 1076, Irgafos 168) [209a], Ultrasonication at room temperature with anhydrous n-hexane or acetone is a suitable soft extraction mode for the determination of aromatic phosphites and phosphonites, such as Ultranox 626 and Sandostab P-EPQ, which easily degrade in heating extraction procedures [210]. 

Sterically hindered phenols and other additives containing thioesters, phosphites, phosphonites and hindered amine moieties were analysed by FAB-MS and LD-FTMS. The laser desorption technique was preferred for analysis of polymer additives because of undesirable fragmentation from FAB experiments [93]. 

In a study of the reactions oi acyclic o-methoxyphenyl-phosphinites (45a), phosphonites (45b) and phosphites (45c) with halogens,the intermediate halogenophosphonium salts (46) are stabilised either by ligand exchange with starting material (not shown) or by elimination of methyl halides to form cyclic phosphoranes ( 47 ) 3 7. ... 

The kinetics of the reaction of trialkyl phosphites, dialkyl aryl-phosphonites, alkyl diarylphosphinites, and triarylphosphines with Sg has been studied the effects of structural changes on the rate (Ph2POR > PhP(OR>2 > P(OR)g > Ph P) and on the Hammett p values are interpreted with respect to the mechanism. A general method to displace mercapto groups from carbon with clean inversion includes... 

The vinylphosphonic esters (77) are obtainable by distillation of the phosphite esters (76)(Scheme 13). No reaction takes place at the vinyl halogen during the preparation of the esters (78), but the interaction of phosphonites and... 

Table 6 Phosphites and Phosphonites. (It should be noted that the phosphite and phosphonite classes of stabiliser are particularly reactive and can be prone to decomposition in extraction solvents and food simulants)... 

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