Bismuthonium salts

Scheme 23 Competitive oxidations between primary and secondary benzyl alcohols by using the bulky bismuthonium salts [90]...

The reaction of alkenyltriphenylbismuthonium salt with ethyl acrylate in the presence of Pd(OAc)2 (2 mol%) afforded both alkenylated and phenylated products in low yields (Scheme 4) [13]. In addition, ligand coupling products of the bismuthonium salt were also formed. 

Quaternary bismuth compounds are generally unstable. When the anionic ligand is chloride or bromide, the compounds decompose spontaneously on standing azides and selenocyanates decompose more rapidly. The perchlorates, tetrafluoroborates, and hexafluorophophates, however, are considerably more stable but eventually decompose. The vibrational spectra of the latter compounds show the presence of the free ion and are consistent with a tetrahedral BiC4 skeleton for the cation. The acetonyltriphenyl compounds, [(C(5H5)3BiCH2COCH3]Y, where Y is C10- 4 or BF- 4, also appear to be true bismuthonium salts. 

Bismuthonium salts in C-C bond formation, 9, 446 in C-heteroatom bond formation, 9, 449 Bismuth ylides... 

Carbon functional groups, attachment to polysilanes, 3, 585 Carbon-heteroatom bond formation via antimony(III) compounds, 9, 428 via antimony(V) compounds, 9, 432 via bismuth(III) compounds characteristics, 9, 440 with copper catalysts, 9, 442 non-catalyzed reactions, 9, 443 with bismuth(V) compounds, 9, 450 with bismuthonium salts, 9, 449 with bismuth ylides, 9, 450 Carbon-heteroatom ligands in tetraosmium clusters, 6, 967 in tetraruthenium clusters, 6, 960... 

Carbon-carbon bond-forming reactions using bismuthonium salts 446... 

Bismuthonium salts, ylides, and imides (a) Y. Matano, H. Suzuki, Bull. Chem. Soc. Jpn. 1996, 69, 2673. (b) Y. Matano, Yuki Gosei Kagaku Kyokaishi 2001, 59,... 

The stability of these bismuthonium salts (82) - (85) depends on the nature of the anionic counterpart and of the fourth ligand. The allyl derivatives (84) are too unstable to be isolated. On the other hand, the tetrafluoroborate salts of the derivatives of the three other types of onium compounds are thermally stable. Ligand coupling- type products are formed with more nucleophilic anions, for example during the attempted exchange of anion with bromide or iodide, or during the slow decomposition of a solution of bismuthonium tosylates in chloroform. ... 

Moreover, the synthesis and good stability of the covalent carbon-bismuth compound in the case of acetone, 2-oxopropyltriphenylbismuthonium perchlorate, excluded this type of intermediate as a common pathway, although this view was questioned by Suzuki et The reaction of the sodium salt of acetylacetone with triphenylbismuth dichloride led to a bismuthonium salt (37) decomposing slowly at room temperature to give eventually 3-phenylpentane-2,4-dione (35). ... 

Recently, unsymmetrical bismuthonium salts bearing four different aryl ligands have been prepared, and the chirality at bismuth has been investigated by H-NMR [990M5668]. The activation energy of isomerization at the bismuth center is strongly dependent on the nucleophilicity of the counter anions as well as the polarity of the solvents employed. This is rationalized by a pseudorotation mechanism via pentacoordinate species at the transition state. 

Quite recently, the bismuthonium salts and ylides bearing an a-ester group have been reported to exhibit similar reactivities to their ketone analogs [99JOC6924]. 

Allyltriphenylbismuthonium salts can be generated in situ, but they decompose rapidly to form allylbenzenes. In the presence of electron-rich arenes, they readily transfer the allyl moiety to arenes to produce the corresponding allylation products [95TL7475]. These bismuthonium salts may be regarded as the allyl cation equivalent for a variety of nucleophiles (Scheme 5.36). 

Generation of Bismuthonium Ylides. The use of NaHMDS as base to deprotonate bismuthonium salts has been reported. Higher yields for the subsequent condensation were usually obtained when using NaHMDS compared to potassium t-butoxide (eq 45). ... 

Allyl- and vinyl-bismuthonium salts are similarly useful and can be elaborated further with a variety of nucleophiles as shown below for the allyl case ... 

---