Triphenylphosphine, reaction with alkyl

Triphenylphosphine. reaction with alkyl halides, 721 Triple bond, electronic structure... 

Triphenylphosphine reacts with alkyl halides to form alkyltriphenylphosphonium salts. Upon reaction with strong bases, the salts release a proton to form an ylide (alkylidenetriphenylphosphorane), which is capable of reacting with aldehydes or ketones providing an unambiguous route to olefins. Since there are virtually no... 

Competitive lithiation cannot occur with monocyclic compounds, and clean a-lithiation was observed with the rhenium bis-(triphenylphosphine) dihydro complex at -78°C (Scheme 13) [89JOM(362)C31 90H(31)383]. So far, only reaction with alkyl halides has been reported, but presumably other electrophiles would react similarly. 

Phenoxaphosphines with P(III), e.g. the 10-phenyl compound (323), are much slower in their reaction with alkylating agents than triphenylphosphine <79PS(7)309). On the other hand, arylation can be achieved (PhBr/AICI3,210 °C, 2 h), giving the 10,10-diphenyl phosphonium salt (327) (isolated as the iodide) <403CS1192, 533CS3746). 

Triphenylphosphine reacts with alkyl halides to form phospho-nium salts. Organolithium bases react with alkyltriphenylphos-phonium salts to give phosphorus ylids, which react with aldehydes and ketones to give alkenes in what is known as the Wittig reaction. 

A useful apphcation of phosphines for replacing a carbonyl function with a carbon—carbon double bond is the Wittig reaction (91). A tertiary phosphine, usually triphenylphosphine, treated with the appropriate alkyl halide which must include at least one a-hydrogen, yields the quaternary salt [1779A9-3] which is then dehydrohalogenated to form the Wittig reagent, methylenetriphenylphosphorane [19943-09-5] an yhde. 

Phosphorus ylides like 1 can be prepared by various routes. The most common route is the reaction of triphenylphosphine 5 with an alkyl halide 6 to give a triphenylphosphonium salt 7, and treatment of that salt with a base to give the corresponding ylide 1 ... 

It is possible to replace one isocyanide by triphenylphosphine, or to replace two isocyanides with diphos, giving phosphine analogues of these complexes. These species are not available from analogous reactions of phosphine-palladium(O) and (II) complexes. Reactions with active alkyl halides proceeds with oxidation nitric oxide also oxidizes these complexes. [Eqs. (31, 32)]. 

Since hydrogen peroxide, like alkyl hydroperoxides, can be alkylated by alkyl bromide plus silver trifluoroacetate (Eq. 19, R = H),35) an attractive variation of the silver-salt-induced dioxabicyclization uses cis- 1,3-dibromocycloalkane 43 as starting material. Thus Porter and Gilmore obtained 2,3-dioxabicyclo[2.2.1]heptane 9 in 30-40% yield from c s-l,3-dibromocyclopentane, which was itself obtained from the corresponding c/s-diol by reaction with triphenylphosphine dibromide (Eq. 31 R = R = H)36). 

Considerable interest has developed in the method of conversion of alcohols, by their reaction with carbon tetrachloride and tertiary phosphines (usually triphenylphosphine), into the corresponding alkyl chlorides.65 The reaction is considered to proceed by an ionic mechanism involving nucleophilic displacement on halogen, as shown. 

The oxidative addition is quite general with alkyl, allyl, benzyl, vinyl, and aryl halides as well as with acyl halides to afford the palladium (II) complex VII. The frans-bis( triphenylphosphine )alkylpalladium halides can also be carbonylated in an insertion reaction to give the corresponding acyl complexes, the stereochemistry of which (17, 18) proceeds with retention of configuration at the carbon bonded to palladium. The acyl complex also can be formed from the addition of the corresponding acid halide to tetrakis (triphenylphosphine) palladium (0). 

Various alkyl and acyl halides have been reported (39, 40, 41, 42, 43, 44) to undergo addition to terakis(triphenylphosphine)palladium(0). In addition, the analogous reaction with the halides listed in Table III has been carried out. 

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