1 - triphenylphosphonium tetrafluoroborate

Cyclopropylidenetriphenylphosphorane (1) generated by treatment of cyclopropyltriphenyl-phosphonium tetrafluoroborate (4) with lithium diisopropylamide, reacts with dialkyl disulfides (diphenyl disulfide does not react) or 7V-(phenylsulfanyl)succinimide in tetrahydrofuran to afford [1 -alkylsulfanyl(cyclopropyl]triphenylphosphonium tetrafluoroborates (5). The latter are useful three-carbon synthons, suitable for pentannulation reactions, as demonstrated with enolates of 2-methoxycarbonyl-4-methylcyclohept-4-enone and -0x0 esters. ... 

The anions generated from substituted ethyl acetylacetates 15 and related compounds reacted with (1 -ethoxycarbonylcyclopropyl)triphenylphosphonium tetrafluoroborate (14) to give diethyl cyclopent-l-ene-l,3-dicarboxylates 16 and 17 via 1,5-addition, ring opening with ylide formation, and intramolecular Wittig reaction.The reaction products were obtained in high yields. The location of the endocyclic double bond depended on the experimental conditions. 

Depending on substituents the reaction of a-hydroxyketones with (2,2-diethoxyvinylidene)-triphenylphosphorane or (2,2-diethoxyvinyl)triphenylphosphonium tetrafluoroborate yields 2,2-diethoxy-2,5-dihydrofurans or 2-ethoxyfurans (Equation (28)) <94ZN(B)389>. 

The radical-mediated addition of triphenylphosphonium tetrafluoroborate to alkenes in the presence of initiators gave the corresponding phosphonium salts, Wittig reagents, in excellent yields and up to gram scale. " ... 

Meanwhile, it was found by Asai and colleagues [48] that tetraphenylphosphonium salts having such anions as Cl, Br , and Bp4 work as photoinitiators for radical polymerization. Based on the initiation effects of changing counteranions, they proposed that a one-electron transfer mechanism is reasonable in these initiation reactions. However, in the case of tetraphenylphosphonium tetrafluoroborate, it cannot be ruled out that direct homolysis of the p-phenyl bond gives the phenyl radical as the initiating species since BF4 is not an easily pho-tooxidizable anion [49]. Therefore, it was assumed that a similar photoexcitable moiety exists in both tetraphenyl phosphonium salts and triphenylphosphonium ylide, which can be written as the following resonance hybrid [17] (Scheme 21) ... 

During the photolysis of a-diazophosphonium salts, the skeletons of the reactants are preserved. Excluding a plausable Wolff rearrangement, only the O/H insertion product of the carbene with the solvents can be obtained. Diazophosphonium tetrafluoroborate (6), formed by UV irradiation in methanol under a nitrogen atmosphere and subsequent anion exchange with sodium tetraphenylborate, yields the stable (2-methoxy-2-oxopropyl)-triphenylphosphonium tetraphenylborate (7) (equation 4)31. 

Cyclopropylidenetriphenylphosphorane (1) reacts with alkyl chloroformates under mild conditions affording [l-(alkoxycarbonyl)cyclopropyl]triphenylphosphonium chlorides (2), the counterion being readily exchanged by treatment with sodium tetrafluoroborate. ... 

C33H3COb02 , 1,6-BisUricobalt nonacarbonyl)-2,3-(dicobalt hexacar-bonyl)hexa-4-yne - benzene, 35B, 505 C3 3H2 eBF4Fe02P, (1-Triphenylphosphonium-2-phenyl-vinyl)-(T -cyclo-pentadienyl)dicarbonyl iron tetrafluoroborate, 45B, 890 C3 3H2 7F6O4PRU, 7 -Cyclopentadienyl (1, 3,4-17- (1, 2-dimethoxycarbonyl-5,5,5-trifluoro-3-trifluoromethylpent-1,3-dienyl))triphenylphos-phineruthenium, 42B,. 637... 

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