Triphenylphosphine, reduction

Other methods for a-hydroxy ketone synthesis are addition of O2 to an enolate followed by reduction of the a-hydroperoxy ketone using triethyl phosphite 9 the molybdenum peroxide-pyridine-HMPA oxidation of enolates 10 photooxygenation of enol ethers followed by triphenylphosphine reduction 11 the epoxidation of trimethyl silyl enol ethers by peracid 1 - the oxidation of trimethylsilyl enol ethers by osmium tetroxide in N-methylmorpholine N-... 

Under standard reaction conditions, the mechanism of the Heck reaction is more complicated than the textbook pathway shown in Scheme 5. The active catalyst responsible for oxidative addition of the ArX substrate is an anionic Pd species, either I PdCl or L2Pd(OAc), depending on the starting palladium compound, where L is triphenylphosphine. Reduction of the starting palladium salt to a Pd species is carried out by the phosphine. A mechanism that is consistent with spectroscopic and electrochemical data is given in Scheme 13. 

Reductive eliminarion from the acylorganopalladium(II) complex is generally a facile process. The rate is influenced by the solvent polarity and added triphenylphosphine. Reductive Aiiminarinn has been shown to be faster than the elimination of palladium hydride from intermediate (111) in both chloroform and HMPA (Scheme 46). This makes the process useful even for alkyl group acylation. 

Intramolecular cyclization of the unsaturated amide (153) is effected by treatment with palladium(ii) acetate and triphenylphosphine reduction of the resulting mixture of geometrically isomeric esters (154) gives the isoquinolone (155) (Scheme 63)/ ... 

Azido-5 -deoxy-nucleosides auid 5 -azido-2, 5 -dideoxy nucleosides have been prepared by a polymer support method, using polystyrenesulphonyl chloride reagent in conjunction with lithium azide,which on triphenylphosphine reduction yielded the corresponding amino-sugar nucleosides. ... 

Diazopenicillin (34) has been utilized as a starting point for the synthesis of a number of other 6-substituted penicillins. Triphenylphosphine reduction of (34) afforded a phosphine oxide complex of (37), which was converted into (38 z, R = PhOCHj) by acylation followed by borohydride... 

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