Bismuth ylides—

The ylides have been classified on the basis of the heteroalom covalently bonded to the carbanion. Accordingly, they can be differentiated into nitrogen ylide (Scheme 2), sulfur ylide Scheme 3, phosphorus ylide Scheme 4, arsenic ylide Scheme 5, antimony ylide (Scheme 6), bismuth ylide (Scheme 7) and thallium ylide (Scheme 8). 

Scheme 3 shows the conceivable reaction sites of alkenylbismuthonium salts, alkynylbismuthonium salts, bismuth ylides, and bismuth imides in carbon-carbon and carbon-heteroatom bond forming reactions. In the initial step, nucleophiles (Nu) attack the positively charged bismuth(V) center, a-proton or (3-carbon (Scheme 3a, b) whereas electrophiles (El) attack the negatively charged a-carbon or a-nitrogen (Scheme 3c, d). Usually, the resulting bismuth(V) intermediates... 

Scheme 3 Reaction sites of organobismuth(V) reagents in C-C and C-X bond forming reactions (a) alkenylbismuthonium salt (b) alkynylbismuthonium salt (c) bismuth ylide (d) bismuth imide. Nu nucleophile, B base, El electrophile...

C-C Bond Forming Reactions with Bismuth Ylides... 

Bismuth ylides of the type Ph3Bi=CHCOR are generated in solution from... 

In a marked contrast to the lighter pnictogen (P, As, Sb) elements, this class of bismuth ylides readily undergoes Corey-Chaycovsky-type epoxidations with aromatic, aliphatic, and ot,(3-unsaturated aldehydes to afford the corresponding... 

Scheme 9 Reaction of bismuth ylides with aldehydes [45, 46]...

Scheme 11 Reactions of bismuth ylides with a-dicarbonyl compounds [46, 67-70]...

The bismuth ylides, Ph3Bi=CHCOR, do not react with simple ketones and electron-rich olefins probably because of their relatively low electrophilic character. However, Ph3Bi=CHCOR reacts with a-keto esters [46, 67, 68], benzils [46, 67-69], orf/to-quinones [46, 67, 68], and acenaphthenequinone [70] to give epoxides, (9-arovl enolates, 3-hydroxytropones, and 3-hydroxyphenalenones, respectively, accompanied by the formation of Ph3Bi (Scheme 11). In particular, transposition and ring expansion reactions are of interest from a mechanistic point of view, since these reaction modes are unprecedented in ylide chemistry. 

Scheme 15 Reaction of bismuth ylide with organic acids [45]...

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 bismuth ylides 447... 

In a few cases this reaction gives ylides of PhaP and PhsAs, albeit in relatively low yield. In combination with isothiocyanates, some bismuth ylides yield complicated addition products, although the fate of the bismuth atom in these reactions is not determined. Likewise, bismuthonium compounds are finding a growing utility in organic synthesis d. 

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