Triphenylbismuth carbonate

Stmcture (1) is an unstable blue soHd which caimot be obtained in a pure state (167) stmcture (2) [105071-90-7] however, is stable (168). Stmcture (2) was obtained from triphenylbismuth carbonate and dimedone. More recendy a number of bismuthonium yUdes, eg, (3) [119016-81 -8] (169), have been prepared and their reactions studied. 

Barton and coworkers have explored the arylation of various nucleophiles including nitroalkanes using bismuth reagents.105 Reaction of 2-nitropropane with triphenylbismuth carbonate gives 2-nitro-2-phenylpropane in 80% yield.106 Recently, this arylation has been used for the synthesis of unusual amino acids. Arylation of a-nitro esters with triphenylbismuth dichloride followed by reduction gives unique a-amino acids (Eq. 5.68).107... 

Arylation. Although some oxidations with triphenylbismuth carbonate occur with quantitative conversion to (Cf,H,)jBi, some proceed with Bi-C cleavage. Although attempts to trap aryl radicals have failed, this cleavage can be used in a synthesis for transfer of an aryl group from Bi to N.1 Examples ... 

Triphenylbismuth carbonate. ISOXAZOLES Samarium(II) iodide. LACTONES Sodium benzeneselenolate. METHOXYTHIOANISOLES Sodium-Hexamethylphosphoramide. OXAZIRIDINES Iron(II) sulfate. OXETANES Cyanotrimethylsilane. 

The allylic alcohol (273) has also been used in a preparation of 15-oxo-15,20S-dihydrocatharanthine (275a), required for partial synthesis of anhydro-vinblastine (q.v.).125 Oxidation of (273) could be achieved by a variety of oxidizing agents, of which triphenylbismuth carbonate appeared to be the best (Scheme 39). Oxidation of the allylic alcohol group was followed by Michael addition of Nb to the... 

Triphenylbismuth diacetate, (CsHOjBiiOCOCH,), (1). Mol. wt. 558.37, m.p. 162°. The reagent is prepared by reaction of triphenylbismuth carbonate with acetic acid. 

The a-arylation of ketones, such as cyclohexanone, can be achieved using different methods. A convenient route by Pinhey et al.89), reacts cyclohexanone-2-carboxylic esters with aryllead triacetates in pyridine. The protection of the P-carboxylic ester prevents a,a-di- or even higher arylations in a -positions. The ester group can be removed by basic hydrolysis and mild thermal decarboxylation or by heating in wet dimethylsulfoxide with sodium chloride (120-180 °C)90). Barton et al. 91) have found a similar a-arylation route using the less electrophilic triphenylbismuth carbonate. In both cases probably the lead- or bismuth-enolates, respectively, are the first inter-... 

Triphenylbismuth carbonate (2) displays remarkable chemoselecdvity, aUowing alcohol oxidation in the presence of benzenethiol, pyrrolidine, indole, aniline, dimethyl aniline and 3-pyrolidinocholesta-3,S-diene. The diol moiety in (3) is cleaved selectively without oxidizing the dithioacetal function (equation 3). The rate of the stoichiometric oxidative cleavage of ciJ-cyclohexane-l,2-diol to adipic aldehyde with Ph3BiC03 is faster than that of the trans isomer, suggesting the formation of a cyclic organobismuth intermediate (4 Scheme 1). ... 

Clearly there are easily oxidizable groups other than alcohols which might be found within a particular structure, and which can interfere with the oxidative introduction of a carbonyl group. Not surprisingly reagents have been developed which will show chemoselectivity for the oxidation of the alcohol function in such systems. Triphenylbismuth carbonate and p.-oxo-bis(chlorotriphenylbismuth) have been reported as such a chemoselective reagent, and will oxidize alcohols in the presence of other easily oxidized species such as benzenethiol, indole and pyrrole (Section 2.9.3). This reagent also cleaves 1,2-diols. 

Oxidation. Triphenylbismuth carbonate suspended in CH2CI2 is a heterogeneous oxidant for a variety of functional groups. Allylic alcohols are efficiently oxidized to the corresponding unsaturated aldehydes or ketones, even in the presence of a thiol, which is itself oxidized by this reagent to a disulfide, cis- and Irani-1,2-Glycols are cleaved to dialdehydes hydrazones are oxidized to diazocompounds oximes are cleaved to ketones and 1,2-dialkylhydrazines are oxidized to azo compounds. Phenylhydrazones, semicarbazones, tosylhydrazones, aromatic and aliphatic amines, enamines, and enol ethers are inert to 1. 

Triphenylbismuthonium 4,4-dimethyl-2,6-dioxocyclohexylide has also been made by heating dimedone with triphenylbismuth carbonate in refluxing dichloromethane . ... 

The first studies on the application of pentavalent organobismuth derivatives in organic synthesis focused on oxidation reactions. In the course of these studies, when Barton et al treated quinine with triphenylbismuth carbonate (5), the reaction led to a rather modest yield of the expected quininone (34%). Using an excess of the reagent (5) afforded a good yield of a mixture of diastereo-isomeric a-phenylated ketones (75%). 3... 

In the case of 2,6-disubstituted phenols, the nature of the bismuth reagent, the nature of the alkyl substituents and the reaction conditions determined the outcome of the reactions. 2 Thus, in the reactions of 2,6-dimethylphenol (19) with pentaphenylbismuth (4) or with tetraphenylbismuthonium derivatives under basic conditions, ortho C-phenylation resulted in the formation of 6-phenylcyclo-hexadienone (20) in good yield. On the other hand, oxidative dimerisation took place in the reaction of 2,6-dimethylphenol with triphenylbismuth carbonate to afford the diphenoquinone (21) quantitatively 25... 

The behaviour of the most sterically hindered 2,6-di-rerr-butylphenol (25) and its derivatives was very dependent upon the reaction conditions. In the presence of a base favouring electron-transfer (such as BTMG), oxidation reactions took place with triphenylbismuth dichloride or triphenylbismuth carbonate leading to the diphenoquinone (26). Para-phenylation with formation of (27) was observed for the first time in the reaction of the potassium phenolate of 2,6-di-re rr-butylphenol with triphenylbismuth dichloride and in the reaction of the phenol (25) with tetraphenylbismuthonium tosylate in the presence of BTMG. Even ortho- and para-phenylation with concomitant de-rerr-butylation occurred in the reaction of the potassium salt of 2,4,6-tri-re r/-butylphenol with triphenylbismuth dichloride. 2... 

In the case of polyhydroxylic phenols, perphenylation occurred. Thus, phloroglucinol (28) reacted with triphenylbismuth carbonate to give a mixture of 2,4,6-triphenylphloroglucinol (29) and 2,2,4,5-tetraphenylcyclopent-4-en-l,3-dione (30).24 The dione (30) is formed from (29) by phenylation, decarboxylation and oxidation. When a large excess of triphenylbismuth carbonate (5 mol equiv.) was used, the dione (30) was the only isolated product in 60% yield. In contrast, the reaction of phloroglucinol with pentaphenylbismuth led to a complex mixture.25... 

The reaction of dimedone (39) with tetraphenylbismuthonium derivatives and BTMG gave the a,a-diphenyl derivative (40). But when dimedone (39) was treated with triphenylbismuth carbonate, an ylide (41) was obtainedP This ylide was later isolated as a stable crystalline compound. This ylide (41) can also be prepared by reaction of the sodium salt of dimedone either with triphenylbismuth dichloride or with triphenylbismuth oxide. Similarly, Meldrum s acid gave the corresponding bismuthonium ylide with triphenylbismuth carbonate and with triphenylbismuth dichloride.3 36 uch ylides can also be made by decomposition of the appropriate dicarbonyl diazonium derivative in the presence of triphenylbismuthane catalysed by bis(hexafluoroacetylacetonato)copper (II) 37 These ylides react with aldehydes to give cyclopropanes, dihydrofurans and a,p-unsaturated carbonyl... 

Other enolised compounds were also easily arylated. Such was the case of P-ketosulfones, which reacted easily with triphenylbismuth carbonate (5) to afford the corresponding a-phenyl-P-ketosul-fones. This reaction was put to good use in an efficient synthesis of isoflavanone and isoflavone... 

Arylthiols were converted to mixed arylphenylsulfides by reaction with pentaphenylbismuth (4) or with tetraphenylbismuthonium trifluoroacetate (6). Oxidation products were also formed in minor amounts (<15%). On the other hand, thiols were readily converted to the corresponding disulfides by treatment either with triphenylbismuth dichloride (3) or with triphenylbismuth carbonate (5) in the presence of sodium hydride.2533... 

Triphenylbismuth carbonate generally does not react with amines, although phenyl transfer to the amino functionality was first observed during an attempt of oxidation of the hydroxyl function of an aminoalcohol by triphenylbismuth carbonate in chloroform. It also reacted with iV-phenylhydro-xylamine under neutral or basic conditions to give diphenylnitroxyl and iV,iV-diphenylacetamide after reductive acetylation (29-33%). No reaction was noted between triphenylbismuth carbonate and nitrosobenzene. High-yielding -arylation was found in the reaction of amino-alcohols with triarylbismuth diacetate in methylene dichloride under reflux. 5... 

Treatment of triphenylbismuth carbonate with sulfonic acids aifords triphenylbismuth disulfonates, which are converted to triphenylbismuth dichloride by metathesis [86ZAAC(539)110]. 

The reaction of triphenylbismuth carbonate with cyclic 1,3-dicarbonyl compounds, such as dimedone and Meldrum s acid, gives highly stabilized triphenylbismuthonium ylides (Section 3.5.1). Moderately stabilized acyclic bismuthonium ylides can be prepared from triphenylbismuth dichloride and a 1,3-diketone or a 1,3-disulfone in the presence of a suitable base. A similar base-promoted reaction of triphenylbismuth dihalides with Al-sulfonylamines or amides has been used for the preparation of stabilized bismuthine imides bearing the Af-sulfonyl or Af-acyl moiety (Section 3.6.1). 

A solution of acetylacetone (0.15 g, 1.5 mmol) in anhydrous benzene or dichloromethane (7.5 ml) was stirred under argon in the presence of triphenylbismuth carbonate (1.9 g, 3.8 mmol) until the reaction is complete. The reaction mixture was filtered though Celite, the filtrate was evaporated, and the residue was purified by preparative thick layer chromatography or column chromatography to give 3-phenylpentane-2,4-dione (0.10 g, 38% yield) and 3,3-diphenylpen-tane-2,4-dione (0.15 g, 40% yield) [85JCS(P1)2667]. 

---