Allylphosphonium salts

Allylphosphonium salts are synthesized by substitution of allyl halides with PPh3. The use of allyl alcohol, allyl acetate, or nitropropene with a palladium catalyst has also been reported.19 It is shown in this study that the organophosphorous compounds can be obtained by a palladium-catalyzed addition to an allene. A notable aspect of this method is that it can control the stereochemistry of the phosphonium salt, and that (Z)-allylphosphonium salts have been obtained in pure form for the first time. 

The intramolecular cyclization of propenyl or allylphosphonium salts [e.g. (109)] to phosphinolinium or isophosphinolinium salts [e.g. (110)] by polyphosphoric acid (PPA) has been shown109 to proceed via a cation-alkylation mechanism, as suggested in the original report.110... 

The cathodic reduction of allylphosphonium salts gives mainly carbon-phosphor bond cleavage products. However, the electroreduction of a C15 polyenylphosphonium bromide 100 in a HMPA—(Al) system at 85 V provides the C—P bond cleavage product 101 (25 %) along with coupling products 102 (11%) and 103 (6 %) (Scheme 3-39)86). 

The addition of butanol or diethylamine to the allenylphosphonium salt (148) is reported to form the substituted allylphosphonium salts (149), which undergo acid hydrolysis to form (150). ... 

C-C coupling reaction between an arylalkynylstannane with p-bromophenyl-triphenylphosphonium bromide." A stereoselective synthesis of ( )- and (Z)-allylphosphonium salts is afforded by the palladium-catalysed addition of triphenylphosphine to allenes, in the presence of an acid, the stereochemical... 

Reactions. - The equilibrium acidities (pKha) of six p-substituted benzyltriphenylphosphonium salts, and also those of related allylphosphonium salts, have been determined, together with the homolytic bond dissociation enthalpies of the acidic C-H bonds. A study of the data available in the Cambridge Structural Database reveals that tetraphenylphosphonium cations in crystals associate through phenyl-phenyl non-bonded interactions which are attractive, concerted, and widespread in nature. An attractive force of 60-85 kJmoP has been calculated. ... 

A mixture of the allylphosphonate 156 and alkenylphosphonates 157 and 158 was obtained by the Pd-catalyzed hydrophosphorylation of 1,2-heptadiene with 4,4,5,5-tetramethyl-l,3,2-dioxaphospholane-2-oxide (155) using Pd(PPh3)4 as a catalyst. When PdMe2(dppf) was used, the allylphosphonate 156 was obtained regioselectively in 87% yield [51]. The allylphosphonium salts such as 159 were... 

Compounds of this type include allyl sulfonium salts, allyl pyridonium salts, allyloxy pyridonium salts, allylphosphonium salts, etc. The attractive features of this technique include the flexibility of the polymerization conditions that can be tuned to the desired wavelengths. 

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