Oxidants triphenylphosphine oxide

The four-membered ring quickly collapses to give the alkene and triphenylphosphine oxide. Triphenylphosphine oxide is exceptionally stable, and the conversion of triphenylphosphine to triphenylphosphine oxide provides the driving force for the Wittig reaction. 

Treatment of anhydrous oxybis(triphenylbismuth) perchlorate with oxygen-donor bases results in the formation of pentacoordinate cationic complexes [73IC944]. Dimethyl sulfoxide, pyridine iV-oxide, triphenylphosphine oxide and triphenylarsine oxide are commonly employed ligands. 

A potential disadvantage of TPP is that it can oxidize at high temperature into TPP=0 (triphenyl phosphine oxide). Triphenylphosphine oxide is an unreactive material whose presence does not degrade the properties of the resin. If such deactivation of the TPP occurs through oxidation, the kinetics would be made substantially more complicated. 

Direct Borohydride Reduction of Alcohols to Alkanes with Phosphonium Anhydride Activation N-Proovlbenzene. To a solution of 5.56 g (20 mmol) of triphenylphosphine oxide in 30mL of dry methylene chloride at CfC was added dropwise a solution of 1.57 mL (10 mmol) of triflic anhydride in 30mL of dry methylene chloride. After 15 min when the precipitate appeared, a solution of 1.36g (10 mmol) of 3-phenyl-1-propanol in 10 mL of dry methylene chloride was added and the precipitate vanished in 5 min. An amount of 1.5g (40 mmol) of sodium borohydride was added as a solid all at once and the slurry was stirred at room temperature for... 

Triphenylphosphine oxide [791-28-6], C gH OP, and triphenyl phosphate [115-86-6], C gH O P, as model phosphoms flame retardants were shown by mass spectroscopy to break down in a flame to give small molecular species such as PO, HPO2, and P2 (33—35). The rate-controlling hydrogen atom concentration in the flame was shown spectroscopically to be reduced when these phosphoms species were present, indicating the existence of a vapor-phase mechanism. 

Phosphine Oxides. Development of cyanoethylphosphine oxide flame retardants has been discontinued. Triphenylphosphine oxide [791 -28-6] C gH OP, is disclosed in many patents as a flame retardant, and may find some limited usage as such, in the role of a vapor-phase flame inhibitor. 

The peroxo species can oxidize other reactants, Hquids, catalyst, or final product in the subsequent coupling reaction. One example of such oxidation is observed in the preparation of triphenylphosphine (13—15). If this reaction is hydrolyzed in air instead of an inert N2 atmosphere, then the amount of triphenylphosphine oxide increases from less than 1 wt % to greater than 15 wt %. 

Some compounds are named as derivatives of the simple phosphoms hydrides (phosphines). For example, dimethylphosphine [676-59-5], (CH2)3PH triphenylphosphine oxide [791-28-6], (CgH3)3P=0 1,2-dimethyldiphosphine [53684-00-7], CH PHPHCH diethyliodophosphine [20472-47-3], (C2H3)2PI phosphonium iodide [12125-09-6], PH" P tetramethylphosphonium chloride [1941 -19-1], (CH3) P" C1 and phenylphosphonium bromide [55671-96-0], CgH PHjBr-. 

Work at Rhc ne-Poulenc has involved a different approach to retinal and is based on the paHadium-cataly2ed rearrangement of the mixed carbonate (41) to the aHenyl enal (42). Isomerization of the aHene (42) to the polyene (43) completes the constmction of the carbon framework. Acid-catalyzed isomerization yields retinal (5). A decided advantage of this route is that no by-products such as triphenylphosphine oxide or sodium phenylsulfinate are formed. However, significant yield improvements would be necessary for this process to compete with the current commercial syntheses (25—27) (Fig. 9). 

Ring contraction of 2-thiocephems has also been examined as a route to penems. Desulfurization of (82, n = 0) using triphenylphosphine gave mixtures of 5(R)- and 5(5)-penems (121). The stereochemical problem was neatiy overcome by regioselective oxidation to the thiosulfonate (82, n = 2) which underwent stereospecific thermal extmsion of sulfur dioxide (122) to give the S(R)-penem (83). 

The avermectins also possess a number of aUyflc positions that are susceptible to oxidative modification. In particular the 8a-methylene group, which is both aUyflc and alpha to an ether oxygen, is susceptible to radical oxidation. The primary product is the 8a-hydroperoxide, which has been isolated occasionally as an impurity of an avermectin B reaction (such as the catalytic hydrogenation of avermectin B with Wilkinson s rhodium chloride-triphenylphosphine catalyst to obtain ivermectin). An 8a-hydroxy derivative can also be detected occasionally as a metaboUte (42) or as an impurity arising presumably by air oxidation. An 8a-oxo-derivative can be obtained by oxidizing 5-0-protected avermectins with pyridinium dichromate (43). This also can arise by treating the 8a-hydroperoxide with base. 

In the chlorination of 2,4-dichlorophenol it has been found that traces of amine (23), onium salts (24), or triphenylphosphine oxide (25) are excellent catalysts to further chlorination by chlorine ia the ortho position with respect to the hydroxyl function. During chlorination (80°C, without solvent) these catalysts cause traces of 2,4,5-trichlorophenol ( 500 1000 ppm) to be transformed iato tetrachlorophenol. Thus these techniques leave no 2,4,5-trichlorophenol ia the final product, yielding a 2,4,6-trichlorophenol of outstanding quaUty. The possibiUty of chlorination usiag SO2CI2 ia the presence of Lewis catalysts has been discussed (26), but no mention is made of 2,4,5-trichlorophenol formation or content. 

The use of a catalyst such as cadmium oxide increases the yield of dibasic acids to about 51% of theoretical. The composition of the mixed acids is about 75% C-11 and 25% C-12 dibasic acids (73). Reaction of undecylenic acid with carbon monoxide using a triphenylphosphine—rhodium complex as catalyst gives 11-formylundecanoic acid, which, upon reaction with oxygen in the presence of Co(II) salts, gives 1,12-dodecanedioic acid in 70% yield (74). 

Pyridazines form complexes with iodine, iodine monochloride, bromine, nickel(II) ethyl xanthate, iron carbonyls, iron carbonyl and triphenylphosphine, boron trihalides, silver salts, mercury(I) salts, iridium and ruthenium salts, chromium carbonyl and transition metals, and pentammine complexes of osmium(II) and osmium(III) (79ACS(A)125). Pyridazine N- oxide and its methyl and phenyl substituted derivatives form copper complexes (78TL1979). 

The isoxazoles (585) were formed regioselectively from the (dioxoalkyl)phosphonium salts (584) with hydroxylamine hydrochloride, the direction of cyclization being different from that of the nonphosphorus-containing 1,3-dioxo compound (see Chapter 4.16). Aqueous sodium hydroxide converted (585) into the isoxazole (586) and triphenylphosphine oxide. Treatment of (585) with n-butyllithium and an aldehyde gave the alkene (587). With hydrazine or phenylhydrazine analogous pyrazoles were formed (80CB2852). 

A variety of 1-azirines are available (40-90%) from the thermally induced extrusion (>100 °C) of triphenylphosphine oxide from oxazaphospholines (388) (or their acyclic betaine equivalents), which are accessible through 1,3-dipolar cycloaddition of nitrile oxides (389) to alkylidenephosphoranes (390) (66AG(E)1039). Frequently, the isomeric ketenimines (391) are isolated as by-products. The presence of electron withdrawing functionality in either or both of the addition components can influence the course of the reaction. For example, addition of benzonitrile oxide to the phosphorane ester (390 = C02Et) at... 

Hexaazadecalin PE, 3, 543 <75CB1557> Hexakis(benzotriazolyl)hexakis(allylamine)-trisnickel(ll) triphenylphosphine oxide X-ray, 5, 675 <76AX(B)714>... 

This group, which is more stable than the 2-hitrobenzenesulfenamide, has been developed to protect amino acids. It is readily introduced with the sulfenyl chloride (52-74% yield) and is cleaved with triphenylphosphine or 2-thiopyridine N-oxide. It is stable to CF3COOH but can be cleaved with 0.1 M HCl. ... 

Triphenylphosphine oxide [791-28-6] from absolute EtOH. Dried in vacuo. 

Triphenylphosphine oxide is soluble in 60% aqueous ethanol therefore it remains in the filtrate and affords no difficulty. 

The solvated phosphorane adds to the polarized carbonyl with the incipient C-21 methyl group pointing away from the bulk of the steroid nucleus. The newly formed carbon-carbon bond must then rotate in order for the tri-phenylphosphine group and oxygen atom to have the proper orientation for the elimination of triphenylphosphine oxide. This places the C-21 methyl in the CIS configuration. 

Step 2 The oxaphosphetane dissociates to an alkene and triphenylphosphine oxide. 

Triphenylphosphine, pentachlorophenol, or 2-thiopyridine A-oxide. The group is stable to CF3COOH, but can be cleaved with 0.1 M HCl. ... 

Wipf and Miller have reported side-chain oxidation of 3-hydroxy amides with the Dess-Martin periodinane, followed by immediate cyclodehydration with triphenylphosphine-iodine, which provides a versatile extension of the Robinson-Gabriel method to substituted oxazoles. Application of this method was used to prepare the oxazole fragment 10 in 55% overall yield from 3-hydroxy amide 8. 

Ti -Cyclopentadienyl(triphenylphosphine)cobalt reacts with phosphites and forms complexes of 1-alkoxyphosphole oxides 251 (R = Me, Et, Ph) through a step involving (ri -cyclopentadienyl)(phosphite)cobalt (80JA4363). (ri -Cp)Co(PF3)2 reacts with hexafluorobut-2-yne and 252 is formed, which hydrolyzes into 253 (X = OH) [73JCS(CC)583 75JCS(D)197]. The five-member ring has the envelope conformation, in which the carbon atoms are coplanar, and the phosphorus atom deviates from this plane in the direction opposite to the cobalt atom. The heterocycle is a four-electron donor relative to the metal center. 

---