Triphenylphosphine opening

Nucleophilic attack by the triphenylphosphine opens the epoxide, producing a betaine, 1. Proton abstraction from bisphenol A yields the phenoxide anion, 2. The phenoxide reacts with the electrophilic carbon attached to the positive phosphorus, 3, regenerating the catalyst. When the phenol is exhausted, the betaine can decompose into a terminal olefin and triphenylphosphine oxide (the final step in the Wittig... 

Few mechanistic studies have been published on the selectivity of phosphonium compoimds, but one publication describes the role of triphenylphosphine in advancement catalysis (36). Nucleophilic attack by triphenylphosphine opens the... 

Triphenylmethylphosphonium bromide A pressure bottle is charged with a solution of 55 g (0.21 mole) of triphenylphosphine in 45 ml of dry benzene and cooled in an ice-salt bath. A commercially available ampoule of methyl bromide is cooled below 0° (ice-salt bath), opened, and 28 g (0.29 mole, approx. 16.2 ml) is added to the bottle in one portion. The pressure bottle is tightly stoppered, brought to room temperature, and allowed to stand for 2 days. After this time, the bottle is opened and the product is collected by suction filtration, the transfer being effected with hot benzene as needed. The yield of triphenylphosphonium bromide is about 74 g (99%), mp 232-233°. This material should be thoroughly dried (vacuum oven at 100°) before use in preparing the ylide. 

Biernath et al. concluded that phenolic novolac and epoxidized cresol novolac cure reactions using triphenylphosphine as the catalyst had a short initiation period wherein the concentration of phenolate ion increased, followed by a (steady-state) propagation regime where the number of reactive phenolate species was constant.85 The epoxy ring opening was reportedly first order in the steady-state regime. 

It may be concluded that the conversion of functionalized oxiranes into the corresponding aziridines by an azide ring opening followed by a Staudinger ring closure with triphenylphosphine constitutes a general method for the preparation of aziridines with high enantiopurity. 

Ring opening of the oxo derivative of the tetrazolo[l,5- ]pyrimidine ring system has also been reported <1996JHC229>. Treatment of the 6-hydroxyethyl-7-methyl substituted compound 59 with triphenylphosphine gave the phosphinimine derivative 60 in nearly quantitative yield (Scheme 10). 

Oxiranes undergo ring opening with trialkylsilyl chlorides to yield trialkylsilyl chloroethyl ethers [51]. The reaction has been shown to be catalysed by tetra-n-butylammonium chloride, although most studies have used triphenylphosphine as the catalyst. Substituted oxiranes are cleaved by haloalkanes to yield the corresponding l-ch oro-2-aIkoxy-2-substituted alkanes [52] (see Section 9.3). 

Hydrosilylation of o-allylstyrene (82) with trichlorosilane in the presence of 0.3mol% of a palladium catalyst bearing triphenylphosphine has been found to produce a mixture of indane (83) and the open-chain products (84) and (85) (Scheme 11). The reaction of styrene with trichlorosilane gave a quantitative yield of 1-phenyl-l-(trichlorosilyl)ethane whereas allylbenzene did not give silylation products under the same reaction conditions. These results show that the hydropalladation process is operative in the hydrosilylation of styrene derivatives with trichlorosilane catalysed by palladium-phosphine complexes." ... 

The analogous open chain carboxylic acid, Z-non-2-en-4-ynoic acid, when treated with 4-iodoanisole in the presence of a palladium-triphenylphosphine catalyst and potassium carbonate gave a mixture of three products, two of which were isolated (4.41.) z) the pyrone derivative arising from the attack of the anisylpalladium complex at the 4-position, followed by ring closure //) the furane derivative (major product) arising from the... 

The reaction of Grignard reagents with thiophene and benzo[6]thiophene in presence of bis(triphenylphosphine)nickel dichloride catalyst results in ring opening with replacement of C—S bonds by C—C bonds (Scheme 38) (79CC637). Thus phenylmagnesium bromide gives 1,4-diphenylbutadiene and phenylstilbene respectively as a 1 1 mixture of stereoisomers. 

A mixture of epoxides 483 obtained on oxidation of 482 with dimethyldioxirane, when exposed to ferric chloride provided, as the kinetically controlled product, the a-aldehyde 484, which without purification was reduced to the a-alcohol 485. The exclusive formation of 484 is believed to occur via the benzyl cation 486, generated by Lewis-acid opening of the oxirane ring, suffering a stereospecific kinetic 1,2-hydride shift The amino alcohol 487 obtained after sequential removal of O-benzyl and N-tosyl groups from 485, on treatment with triphenylphosphine and iodine in the presence of imidazole furnished the tetracyclic base 488, which was oxidised to the ketone 489. Trapping of the kinetically generated enolate of 489 as the silylether, followed by palladium diacetate oxidation yielded the enone 490. The derived... 

Ring opening of cz s-2,3-dimethyloxirane by triphenylphosphine has been modeled using the B3LYP functional with the 6—3lG(d) basis set.43 The calculations suggest that the first step of the reaction is an SN2 process with simultaneous C-C bond rotation giving an oxaphosphetane intermediate that decomposes to the frans-alkene no betaine intermediate is formed. 

Small Quantities. Wear eye protection, laboratory coat, and nitrile rubber gloves. Work in the fume hood. Triphenylphosphine (1.3 g, 0.005 mol) is dissolved in tetrahydrofuran (30 mL). The solution is slowly added while stirring to household bleach (70 mL) or a calcium hypochlorite solution (5.5 g in 20 mL of water). After stirring for 1 hour, the solution is placed in an open container in the fume hood to allow the tetrahydrofuran to evaporate. The aqueous solution is washed into the drain.6... 

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