Triphenylbismuth Dichloride1


[594-30-9]  · C18H15BiCl2  · Triphenylbismuth Dichloride  · (MW 511.21) (Ph5Bi)

[3049-07-8]  · C30H25Bi  · Pentaphenylbismuth  · (MW 594.53) (Ph4BiOCOCF3)

[83566-43-2]  · C26H20BiF3O2  · Tetraphenylbismuth Trifluoroacetate  · (MW 630.44) (Ph4BiOTs)

[83566-44-3]  · C31H27BiO3S  · Tetraphenylbismuth Tosylate  · (MW 688.63)

(phenylation of phenols,6 ketones and enols,5 and nitro compounds8)

Physical Data: mp 159-160 °C.2

Solubility: sol CH2Cl2, CHCl3, benzene, toluene; insol ether, THF, MeOH.

Preparative Methods: easily prepared2 by oxidation of Triphenylbismuthine either by bubbling Chlorine gas into an ethereal solution of Ph3Bi at 0 °C, or by addition of 1 equiv of Sulfuryl Chloride to a solution of Ph3Bi in CH2Cl2 at -78 °C. The action of Phenyllithium on Ph3BiCl2 leads to pentaphenylbismuth (mp 77-78 °C).2 Addition of 1 equiv of a carboxylic or sulfonic acid to Ph5Bi affords compounds of the type Ph4BiX.3 (Ph4BiOCOCF3: mp 120-132 °C; Ph4BiOTs: mp 155-162 °C).

Handling, Storage, and Precautions: stable white solid; can be stored in the refrigerator in the absence of moisture. Pentaphenylbismuth is a poorly stable violet powder which can be stored under inert gas in the refrigerator for some days. Ph4BiOCOCF3 and Ph4BiOTs are white powders which can be stored in the refrigerator under inert gas for some weeks. These reagents should be used in a fume hood.

Oxidation of Alcohols.4

Treatment of primary or secondary alcohols with (a) Ph3BiCl2 or Ph4BiX in the presence of a strong base (e.g. 1,1,3,3-Tetramethylguanidine, BTMG (t-butyltetramethylguanidine), or 1,8-Diazabicyclo[5.4.0]undec-7-ene) or with (b) Ph5Bi under neutral conditions leads to oxidation to the corresponding carbonyl compounds under mild conditions in moderate to high yields (eq 1). Because of the similar reactivity patterns of these reagents, the system Ph3BiCl2 + base is the reagent of choice, due to its facile preparation and stability. An excess of reagent must be avoided, as possible side reactions such as a-C-phenylation can occur (see below).5 The reaction of salts of tertiary alcohols, e.g. t-BuOLi, with Ph3BiCl2 results in the formation of the O-phenyl ethers e.g. t-BuOPh.4c In the presence of a base such as BTMG, Ph3BiCl2 cleaves glycols efficiently in the same way as Ph3BiCO3.

Phenylation of Phenols.6

The reaction of phenols with organobismuth(V) reagents leads to a variety of products (eq 2). Phenols bearing electron-donating substituents react with Ph3BiX2 or Ph4BiX in the presence of a strong base (BTMG, TMG, NaH, or KH) or with Ph5Bi under neutral conditions to give mostly or only the o-mono- or o,o-di-C-phenylated derivatives. With 2,6-disubstituted phenols, either 6-phenyl-6-methylcyclohexa-2,4-dienone or 4-phenyl-2,6-di-t-butylphenol are obtained, in contrast to the reaction with Ph3BiCO3 which gives diphenoquinones. Unactivated phenols or phenols bearing meta electron-withdrawing substituents afford mixtures of O- and ortho-C-phenylphenols. Phenols bearing para electron-withdrawing substituents give exclusively O-phenyl ethers after thermal decomposition of the aryloxybismuth intermediate. As these O-phenyl ethers can be obtained under milder conditions (neutral, rt) with Triphenylbismuth Diacetate under Cu(OAc)2 catalysis, the present system does not compete efficiently.

Phenylation of Ketones and Enolic Compounds.5

In the presence of a strong base, ketones react with Ph3BiCl2 or Ph4BiX to afford mostly or only the perphenylated derivatives. For example, cyclohexanone affords 2,2,6,6-tetraphenylcyclohexanone in 80% yield with Ph4BiOTs + KH.7 Ph5Bi does not react with nonenolizable ketones, but with enolizable ketones the reaction does take place. Thus 2-phenylethanol is oxidized by Ph5Bi and the aldehyde further reacts to afford, eventually, triphenylacetaldehyde in 69% yield.5 Enolizable compounds such as b-dicarbonyl derivatives react with Ph5Bi under neutral conditions, or with Ph3BiCl2 and Ph4BiX (both in the presence of a strong base), to afford generally the a-perphenylated derivatives. For example, this reaction occurs with acetylacetone, ethyl acetoacetate, ethyl cyclohexanone-2-carboxylate (eq 3), ethyl cyclopentanone-2-carboxylate, diethyl malonate, and dimedone.5,8

With acetylacetone, Ph3BiCl2 and base leads to 3,3-diphenylacetylacetone (74%), whereas Ph4BiOCOCF3 in benzene under reflux in the absence of base gives a moderate yield of the 3-monophenyl derivative (34%). In the case of dimedone and Meldrum's acid, the reaction of their sodium salts with Ph3BiCl2 leads only to the stable crystalline bismuthonium ylides.9 In an application in natural products chemistry, high yields of 3-phenyl-4-hydroxycoumarins have been obtained from the reaction of 4-hydroxycoumarins with Ph5Bi at -23 °C.10 With caprolactam-type malonic derivatives, completely different results are observed, depending on the reagent used. Thus 3-cyano-ε-caprolactam reacts only with Ph5Bi to give 74% of 3-cyano-3-phenyl-ε-caprolactam; 3-ethoxycarbonyl-ε-caprolactam does not react with Ph5Bi and gives only the N-phenylcaprolactam derivative through reaction with Ph3BiCl2 and base.11

Phenylation of Nitro Compounds.

In the presence of BTMG, 2-nitropropane reacts with Ph3BiCl2 or Ph4BiOTs to produce a-nitrocumene (86 or 77% respectively).8 The reaction using Ph3BiCl2 and TMG has been applied to the synthesis of a-methyl-a-phenylglycine via arylation of a-nitropropionic acid esters.12

1. (a) Barton, D. H. R.; Finet, J. P. PAC 1987, 59, 937. (b) Abramovitch, R. A.; Barton, D. H. R.; Finet, J. P. T 1988, 44, 3039. (c) Finet, J. P. CRV 1989, 89, 1487. (d) Freedman, L. D.; Doak, G. O. In The Chemistry of the Metal-Carbon Bond; Hartley, F. R., Ed.; Wiley: New York, 1989; Vol. 5, Chapter 9.
2. (a) Wieber, M. Gmelin Handbuch der Anorganische Chemie; Springer: Berlin, 1977; Band 47, Bismut-Organische Verbindungen, p 15. (b) Wittig, G.; Clauss, K. LA 1952, 578, 136.
3. Barton, D. H. R.; Charpiot, B.; Dau, E. T. H.; Motherwell, W. B.; Pascard, C.; Pichon, C. HCA 1984, 67, 586.
4. (a) Barton, D. H. R.; Kitchin, J. P.; Motherwell, W. B. CC 1978, 1099. (b) Barton, D. H. R.; Kitchin, J. P.; Lester, D. J.; Motherwell, W. B.; Papoula, M. T. B. T 1981, 37, W73. (c) Dodonov, V. A.; Gushchin, A. V.; Grishin, D. F.; Brilkina, T. G. ZOB 1984, 54, 100.
5. Barton, D. H. R.; Blazejewski, J. C.; Charpiot, B.; Finet, J. P.; Motherwell, W. B.; Papoula, M. T. B.; Stanforth, S. P. JCS(P1) 1985, 2667.
6. (a) Barton, D. H. R.; Bhatnagar, N. Y.; Blazejewski, J. C.; Charpiot, B.; Finet, J. P.; Lester, D. J.; Motherwell, W. B.; Papoula, M. T. B.; Stanforth, S. P. JCS(P1) 1985, 2657. (b) Barton, D. H. R.; Yadav-Bhatnagar, N.; Finet, J. P.; Khamsi, J.; Motherwell, W. B.; Stanforth, S. P. T 1987, 43, 323.
7. Barton, D. H. R.; Charpiot, B.; Ingold, K. U.; Johnston, L. J.; Motherwell, W. B.; Scaiano, J. C.; Stanforth, S. P. JACS 1985, 107, 3607.
8. Barton, D. H. R.; Finet, J. P.; Giannotti, C.; Halley, F. JCS(P1) 1987, 241.
9. Suzuki, H.; Murafuji, T.; Ogawa, T. CL 1988, 847.
10. Barton, D. H. R.; Donnelly, D. M. X.; Finet, J. P.; Stenson, P. H. T 1988, 44, 6387.
11. Akhtar, M. S.; Brouillette, W. J.; Waterhous, D. V. JOC 1990, 55, 5222.
12. Lalonde, J. J.; Bergbreiter, D. E.; Wong, C.-H. JOC 1988, 53, 2323.

Jean-Pierre Finet

Université de Provence, Marseille, France

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