Triphenyl phosphite, reactions

Rate Constants and Activation Energies of Triphenyl Phosphite Reaction with Different Hydroperoxide [21]... 

The preparations described here are developed from published work by Malatesta et al.5 and from more recent studies in the contributors own laboratory.2 The cobalt and nickel complexes are prepared by reduction of the corresponding metal nitrates with sodium tetrahydroborate in the presence of excess ligand, whereas the syntheses of the rhodium and platinum complexes involve simple ligand exchange processes. The preparative routes are suitable for use with triphenyl- or p-substituted triphenyl phosphites reactions involving o- or m-substituted triphenyl phosphites give much reduced yields of products which are difficult to crystallize and are very air-sensitive. These features probably reflect the unfavorable stereochemistry of the o- and m-substituted ligands. 

Phosphites, such as triisopropyl and triphenyl phosphite, are weaker electron donors than the corresponding phosphines, but they are used in some reactions because of their greater rr-accepting ability. The cyclic phosphite trimethylol-propane phosphite (TMPP) or 4-ethyl-2,6,7-trioxa-l-phosphabicyclo[2.2.2]oc-tane (8), which has a small cone angle and small steric hindrance, shows high catalytic activity in some reactions It is not commercially available, but can be prepared easily[27]. 

Phosphites. Tertiary phosphites are also commonly used and are particularly effective ia most mixed metal stabilizers at a use level of 0.25—1.0 phr. They can take part ia a number of different reactions duting PVC processing they can react with HCl, displace activated chlorine atoms on the polymer, provide antioxidant functionaHty, and coordinate with the metals to alter the Lewis acidity of the chloride salts. Typical examples of phosphites are triphenyl phosphite [101 -02-0], diphenyl decyl phosphite [3287-06-7], tridecyl phosphite [2929-86-4], and polyphosphites made by reaction of PCl with polyols and capping alcohols. The phosphites are often included in commercial stabilizer packages. 

The aHphatic iodine derivatives are usually prepared by reaction of an alcohol with hydroiodic acid or phosphoms trHodide by reaction of iodine, an alcohol, and red phosphoms addition of iodine monochloride, monobromide, or iodine to an olefin replacement reaction by heating the chlorine or bromine compound with an alkaH iodide ia a suitable solvent and the reaction of triphenyl phosphite with methyl iodide and an alcohol. The aromatic iodine derivatives are prepared by reacting iodine and the aromatic system with oxidising agents such as nitric acid, filming sulfuric acid, or mercuric oxide. 

Dicyclopentadiene has produced some interesting results. With rhodium catalyst at 115°C in tetrahydrofuran (THF), the dialdehyde was produced in good yield at 180°C that reaction proceeds further to form the diol in 67% yield (67). With a rhodium catalyst modified by excess triphenyl phosphite, the unsaturated monoaldehyde was obtained in a rapid reaction under very mild conditions (68, 69). The nonstrained 5-membered ring olefin required more strenuous conditions for hydroformylation. Either compound could be obtained in good yield by proper choice of conditions. 

The effect of ligands has been studied (49). Phosphites, instead of phosphine, affect the ratio of isomers 47 and 48. Using triphenyl phosphite in the reaction of acetic acid at 50°C in 0.5 hour, 75% conversion of butadiene was attained. The selectivity to the acetoxyoctadienes was 93%, and the ratio of 47 to 48 was 92 8. Trimethylolpropanephosphite... 

The stoichiometry of this reaction is usually close to unity [6-9]. Thus, cumyl hydroperoxide oxidizes triphenyl phosphite in the stoichiometry A[ROOH]/A[Ph3P] from 1.02 1 to 1.07 1, depending on the proportion between the reactants [6], The reaction proceeds as bimolecular. The oxidation of phosphite by hydroperoxide proceeds mainly as a heterolytic reaction (as follows from conservation of the optical activity of reaction products [5,11]). Oxidation is faster in more polar solvents, as evident from the comparison of k values for benzene and chlorobenzene. Heterolysis can occur via two alternative mechanisms... 

Since this reaction is not affected by hydroquinone and galvinoxyl and does not initiate polymerization of styrene, it obviously occurs without the formation of free radicals. The kinetic parameters of the reactions of three hydroperoxides with triphenyl phosphite in different solvents are given in Table 17.2 [21]. 

In addition to the decay of hydroperoxides, metal complexes accelerate the reaction of phosphite with peroxyl radicals [90,91]. Phosphite forms a complex with the metal ion, and the formed complex terminates the chains more rapidly than phosphite does alone. For example, triphenyl phosphite terminates the chains in oxidized styrene with fkq = 2 x 103L mol-1 s-1 at T 393 K and the complex of this phosphite with CuCI does it with fkq = 2 x 105L mol-1 s 1, i.e., two orders of magnitude more rapidly. The values of / and kq for three phosphites and six complexes (phosphite with CuCI) are given in Table 17.10. 

Preparation of 0,0-diphenyl 2-methylthio-l-(JV-phenylthioureido)ethylphosphonate — Reaction of triphenyl phosphite with an imide generated in situ... 

To a solution of triphenyl phosphite (6.2 g, 0.02 mol) and thiomethoxy-acetaldehyde (2.25 g, 0.025 mol) in glacial acetic acid (18 ml), powdered N-phenylthiourea was added in a single portion. The reaction mixture was stirred at room temperature for 30 min and then for 30 min at 80°C. After the mixture was cooled to room temperature, water (5 ml) was added and the solution was maintained at room temperature for 10 h. The precipitate was removed by suction filtration, washed with 1 1 acetic acidtwater (2 x 10 ml), dried over potassium hydroxide in an evacuated dessicator, and recrystallized from chloroform/ methanol. In this manner there was isolated pure 0,0-diphe-nyl 2-methylthio-l-(iV-phenylthioureido)ethylphosphonate (8.61 g, 94%) of mp 136 to 138°C, which exhibited spectra and analytical data in accord with the proposed structure. 

Some examples of the dioxolenium ion alkenylation reaction are shown in Scheme 8.29 [58], The use of AgC104 on Celite (easier to handle than pure AgC104) and triphenyl phosphite was stated to improve the reproducibility in these reactions. At present, the method is not applicable to alkylzirconocene chlorides. 

Dias, M. L. and Silva, A. P. F Transesterification reactions in triphenyl phosphite additivated-poly(ethylene terephthalate)/poly(ethylene naphtha-late) blends, Polym. Eng. Sci., 40, 1777 (2000). 

The stereochemistry of the seven-membered cyclic phosphites (94), (95), and (96), prepared from the base-catalysed reaction of triphenyl phosphite and the corresponding diol, has been investigated by 1H, 13C, and 31P n.m.r.73 The results suggest that each of the three heterocycles adopts a different conformation in solution. 

Aryl phosphites were among the first ligands that were extensively studied. The results obtained with triphenylphosphine and triphenyl phosphite are strikingly similar at low ligand concentrations. At higher ligand metal ratios phosphites may retard the reaction. The electronic and steric properties of the phosphite have a large effect on the rate and selectivity of the reaction. 

Catalytic one-pot procedure. Since in the described teUuronium ylide olefmation tellurox-ide is formed as a by-product, and the telluroxide is susceptible to reduction by triphenyl phosphite, a catalytic procedure can be employed, providing a practical one-pot synthesis of a, -unsaturated esters and ketones (method E). By this procedure, a catalytic amount of n-dibutyl telluride reacts with the a-bromoester or a-bromoketone, and the formed tel-luronium salt is converted in situ under phase transfer conditions (solid KjCOj/trace HjO) into the ylide, which reacts in turn with the aldehyde, giving the olefin. Since the reaction is performed in the presence of triphenyl phosphite, the formed dibutyl telluroxide is reduced back to the dibutyl telluride, which is then recycled. 

Method E - catalytic procedure (typical procedure). Benzaldehyde (106 mg, 1.0 mmol), methyl bromoacetate (165 mg, 1.1 mmol), triphenyl phosphite (356 mg, 1.2 mmol), dibutyl telluride (48 mg, 0,2 mmol), KjCOj (179 mg, 1.3 mmol) and THF (4 mL) are mixed and stirred at 50°C for 13 h (monitored by TLC). The reaction mixture is filtered rapidly through a small amount of SiOj with EtOAc as the eluent to remove inorganic salts and dibutyltellurium oxide. Preparative TLC with EtOAc/petroleum ether at 60-90°C (1 9) as the eluent yields 3-phenylpropenoate (160 mg (98%)). 

The reaction of singlet oxygen with conjugated double bonds usually is a 1,4-cycloaddition leading to formation of derivatives of the 1,2-diox -ene ring system. This can be achieved either by photooxidation or by reaction in the presence of triphenyl phosphite-ozone adduct (Section Vin.D.2), shown in equations 85 and 86 . ... 

The relative amounts of the products depend on irradiation time, and the formation of the bis (triphenyl phosphite) chromium complex may be almost completely avoided by following the reaction with thin layer chromatography. The diastereoisomers are air stable and reasonably soluble in most organic solvents. Their infrared spectra exhibit a metal carbonyl band at 1925 cm 1 (i>co ester at 1729 cm"1) and a metal thiocarbonyl band at 1925 cm"1 (CH2C12 solution). The NMR spectra. I 5ch3 at 1.87 ppm 5co3CH3 at 3.77 ppm II 6ch3 at 1.77... 

When the ratio of template to acid is close to 0.5, the viscosity of the product is more than 3 times higher than the viscosity of the polymer obtained without the template. PEO participates in the change of local concentration by interaction with carbonyl groups, but not in the activation. Solution of LiCl in N-methylpyrrolidone with PlOCeHsls was found very effective system for synthesis of amides by the direct reaction of acids with amines in the presence of polymeric matrix. High molecular weight poly(aminoacids) obtained by direct polycondensation reaction, promoted by triphenyl phosphite and LiCl in the presence of poly(vinylpyrrolidone), were synthesized by Higashi et al The results for polymerization of L-leucine in the presence of poly(vinyl pyrrolidone) are presented in the Table 6.3. 

---