Phosphite esters

3 Phosphite Esters. Sugar phosphites do not occur naturally, but play a key role in DNA synthesis, particularly automated DNA synthesis. Their reactions are thus at the heart of much modern biotechnology. Many systems 

The formation of retained product via collapse of a phosphorane is usually negligible. 

The barrier to inversion about phosphorus in phosphites is large enough for tricovalent phosphites chiral at phosphorus to be configurationally stable, but the conditions for the coupling of phosphoramidites epimerised them at P about 10 times faster than it coupled them, although the oxidation of phosphites to phosphates and thiophosphates proceeded with complete retention of phosphorus stereochemistry.  

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When the phenol reactant is 2,4-di-/ f2 -butylphenol, a phosphite ester with greater hydrolytic stabiUty is produced. 

The primary use for 2,4-di-/ f2 -butylphenol is in the production of substituted triaryl phosphites. 2,4-Di-/ f2 -butylphenol reacts with phosphoms trichloride typically using a trialkylamine or quaternary ammonium salt as the catalyst. Hydrogen chloride is formed and either complexed with the amine or Hberated as free hydrogen chloride gas forming the phosphite ester, tris(2,4-di-/ f2 -butylphenyl)phosphite [31570-04-4] (58). The phosphite-based on... 

Phosphite esters are formed readily by the reaction of phosphoms haUdes and isopropyl alcohol. Eor example, triisopropyl phosphite [116-17-6] is prepared from phosphoms trichloride [7719-12-2] and isopropyl alcohol at low temperatures ia the presence of an acid scavenger, eg, pyridine [110-86-1]. 

Sulfides orthio derivatives Metallic derivatives of thio ethers and disulfides, usually mixed with organic phosphite esters long-chain alkyl thienyl ketones Lubricating oils boiler water... 

Another method for slowing oxidation of rubber adhesives is to add a compound which destroys the hydroperoxides formed in step 3, before they can decompose into radicals and start the degradation of new polymer chains. These materials are called hydroperoxide decomposers, preventive antioxidants or secondary antioxidants. Phosphites (phosphite esters, organophosphite chelators, dibasic lead phosphite) and sulphides (i.e. thiopropionate esters, metal dithiolates) are typical secondary antioxidants. Phosphite esters decompose hydroperoxides to yield phosphates and alcohols. Sulphur compounds, however, decompose hydroperoxides catalytically. 

Organic derivatives fall into 4 classes RP0(0H)2, HP0(0R)2, R P0(0R)2 and the phosphite esters R(OR)3 this latter class has no purely inorganic analogues, though it is, of course, closely related to PCI3. Some preparative routes have already been indicated. Reactions with alcohols depend on conditions ... 

Iridium-catalyzed hydrogen transfer from aqueous phosphite esters or phosphorous acid is an effective way of producing axial alcohols (77,25,J4,46,57). 

The early work of Kennerly and Patterson [16] on catalytic decomposition of hydroperoxides by sulphur-containing compounds formed the basis of the preventive (P) mechanism that complements the chain breaking (CB) process. Preventive antioxidants (sometimes referred to as secondary antioxidants), however, interrupt the second oxidative cycle by preventing or inhibiting the generation of free radicals [17]. The most important preventive mechanism is the nonradical hydroperoxide decomposition, PD. Phosphite esters and sulphur-containing compounds, e.g., AO 13-18, Table la are the most important classes of peroxide decomposers. 

Olefination Reactions Involving Phosphonate Anions. An important complement to the Wittig reaction involves the reaction of phosphonate carbanions with carbonyl compounds 253 The alkylphosphonic acid esters are made by the reaction of an alkyl halide, preferably primary, with a phosphite ester. Phosphonate carbanions are generated by treating alkylphosphonate esters with a base such as sodium hydride, n-butyllithium, or sodium ethoxide. Alumina coated with KF or KOH has also found use as the base.254... 

The Mitsunobu conditions also can be used to effect a variety of other important and useful nucleophilic substitution reactions, such as conversion of alcohols to mixed phosphite esters.56 The active phosphitylating agent is believed to be a mixed phospho-ramidite. 

The reaction with phosphite esters is known as the Michaelis-Arbuzov reaction and proceeds through an unstable trialkoxyphopsphonium intermediate. The second stage is another example of the great tendency of alkoxyphosphonium ions to react with nucleophiles to break the O—C bond, resulting in formation of a phosphoryl P—O bond. 

Applications Extraction is typically accomplished by refluxing the polymer in an appropriate solvent for l-48h [84,199]. In many cases, ultrasonic exposure reduces the extraction time [90,200], According to Table 3.5 there are several reports of US extraction from polymers. Ultrasonic extraction has been used for HDPE/(BHT, Irganox antioxidants, Isonox, Cyasorb, Am 340, MD 1024, Irgafos 168) [56], LDPE/Chimassorb 81 [201], SBR/tri(nonylphenyl) phosphite [200], HDPE/(Tinuvin 770, Chimassorb 944) [114], etc. Nielson [90] compared the recoveries obtained for a variety of analytes from PP, LDPE and HDPE with Soxhlet, ultrasonic bath and microwave oven. For all samples, the ultrasonic extraction could be achieved within 1 h. For LDPE and PP most compounds (except Irganox 1010) were extracted within 10 min. Further experiments by Nielson [56] on extraction from HDPE confirmed these results. Where phosphite antioxidants (such as Irgafos 168) are present the use of the solvent mixture DCM-cyclohexane was preferred as it prevented hydrolysis of the phosphite by extraction solvents such as alcohols [56]. Similarly, phosphite esters also undergo hydrolysis... 

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... 

The organic chemistry of phosphorus includes many compounds, but the phosphite esters are especially useful. These compounds can be prepared by the reaction of PC13 with an alcohol. 

The bonds in PC13 are reactive toward many compounds that contain OH groups. Consequently, alcohols react with PC13 to produce trialkyl phosphite esters. 

Preparation of 2,3-dioleoyloxypropylphosphonic acid — Reaction of an alkyl halide with a silyl phosphite ester... 

Taira, K. and Gorenstein, D.C., Experimental tests of the stereoelectronic effect at phosphorus Michaelis-Arbuzov reactivity of phosphite esters, Tetrahedron, 40, 3215, 1984. 

Evans, D.A., Hurst, K.M., and Takacs, J.M., New silicon-phosphorus reagents in organic synthesis. Carbonyl and conjugate addition reactions of silicon phosphite esters and related systems, /. Am. Chem. Soc., 100, 3467, 1978. 

An allylic phosphorus ester rearrangement to form a new C-P bond has been reported under photochemical conditions.179 Under irradiation in the presence of 9,10-dicyanoanthracene, an allylic phosphite ester undergoes rearrangement to form the corresponding allyl-icphosphonite ester (Equation 4.40). Benzophenone serves only poorly as a photosensitizer in this reaction. 

Two reports are available on the rearrangement of mixed vinyl phosphite esters to produce phosphonate diesters in moderate yield.94 95 In both instances, the vinyl phosphite esters were prepared by reaction of the dialkyl phosphorous chloride with highly enolized carbonyl compounds. The mixed ester products undergo thermal rearrangement to the phosphonate diesters (Figure 6.25). 

Phosphine complexes, osmium, 19 642 Phosphine coordination complexes, of uranium, 25 436 Phosphine derivatives, 19 28 Phosphine oxide(s), 11 495-496 19 66 predicted deviations from Raoult s law based on hydrogen-bonding interactions, 8 814t in salicylic acid manufacture, 22 8 Phosphine oxide diols/triols, 11 501 Phosphine selenides, 22 90 Phosphinic acid, 19 20, 54-55 Phosphinic anhydride, 11 499 Phosphinothricin acetyltransferase (PAT) proteins, 13 360 Phosphite esters, 19 20 Phosphites, in VDC polymer stabilization, 25 720... 

As already mentioned (p. 99) ethylene oxide reacts with phosphorus trichloride to give ultimately tri-(2 - chloroethyl) phosphite, P(0CH2CH2C1)3.1 In a similar manner CgHgOPC and (C6H50)2PC1 will give the corresponding mixed phosphite esters. 

Recently (22,23), we observed that quinine catalyzes the 1,2-addition of phosphite esters to benzaldehydes. When the aldehyde has an ortho substituent, preferably one that aids in restricting the rotation of the aldehyde group, asymmetric induction takes place. In these reactions quinine is 20 times as effective a catalyst as is triethylamine (83) (eq. [23]). Although the e.e. in the reaction shown in eq. [23] is 26% when R = nitro, this percentage rises to 80% when di-/-butyl phosphite is used (see also eq. [3]). 

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