[603-33-8] · C18H15Bi · Triphenylbismuthine · (MW 440.31)
Alternate Name: triphenylbismuth.
Physical Data: mp 77.6 °C.2
Solubility: CH2Cl2, CHCl3, CCl4, benzene, toluene, ether, THF, ethyl acetate; insol H2O, alcohols; decomposed in acidic solvents.
Preparative Method: conveniently prepared by reaction of Phenylmagnesium Bromide with BiCl3 in ether.3
Handling, Storage, and Precautions: must be stored in dark bottles in the absence of moisture or acidic vapors. Use in a fume hood.
Triphenylbismuthine acts as a catalyst in the oxidative cleavage of a-glycols by N-Bromosuccinimide or N-Bromoacetamide in the presence of Potassium Carbonate to give the corresponding aldehydes and/or ketones. The oxidation is best performed by dropwise addition of an acetonitrile solution of NBS (4 equiv) to the mixture of the glycol, Ph3Bi (0.01-0.1 equiv), and K2CO3 (4 equiv) in acetonitrile-water (99:1) in the dark at room temperature (eq 1). Yields are similar or better than those obtained with Lead(IV) Acetate, periodic acid and its salts, or the stoichiometric Triphenylbismuth Carbonate reagent. In contrast with these reagents, which cleave only cis-decalin-9,10-diol, the catalytic system cleaves both the cis- and the trans-decalin-9,10-diol isomers at nearly the same rate.
Although there is no reaction between Ph3Bi and Copper(II) Acetate, triphenylbismuthine can transfer a phenyl group to alcohols, phenols, or amines when a stoichiometric amount of copper diacylate is used.
When primary or secondary alcohols are treated with Ph3Bi in the presence of copper diacetate (Ph3Bi:Cu(OAc)2 = 1:2) without solvent in sealed ampules, the O-phenyl ethers are formed in 43-91% yields (based on the bismuth reagent) at a very slow rate (several days at rt) (eq 2). No reaction with phenol has been described under these conditions. However, when a CH2Cl2 solution of 3,5-di-t-butylphenol is treated with a mixture of Ph3Bi (1.2 equiv), Cu(OAc)2 (2 equiv), and Et3N (4 equiv), the corresponding O-phenyl ether is obtained in 44% yield after 10 h at rt. These O-phenylation reactions, particularly of phenols, are better performed with the more general copper-catalyzed Triphenylbismuth Diacetate system.
Amines react smoothly at rt with Ph3Bi (1.2 equiv) and Cu(OAc)2 (0.5 equiv) to give high yields of N-mono- or N,N-diphenylated amines. Generally, monophenylated compounds are obtained with primary amines (eq 3) in variable yields, depending upon the basicity and steric hindrance of the substrate (6% for p-nitroaniline, 25% for mesitylamine, but 82% for p-methoxyaniline). With n-butylamine, the monophenyl (60%) and diphenyl (38%) derivatives are obtained. This reaction is less efficient than the related copper-catalyzed triphenylbismuth diacetate system. However, since Ph3Bi is commercially available, this reaction is of interest for the monophenylation of anilines and a variety of aliphatic and heterocyclic amines.
Triarylbismuthines Ar3Bi (Ar = Ph, p-MeC6H4, p-MeOC6H4) react with Pd(OAc)2 (1 equiv) and Triethylamine (2 equiv) in HMPA to afford quantitatively the corresponding biaryl after heating for 10 min at 65 °C. When the reaction is performed in presence of acyl chlorides at 65 °C for 5 h in HMPA, phenyl ketones are obtained in 89-96% yields (eq 4). In the absence of the catalyst, phenyl ketones are also formed but in low yields.9
Triphenylbismuthine can also function as a catalyst or cocatalyst in the polymerization of hydrocarbons,1c and as a source of phenyl radicals under photolytic conditions.4
Université de Provence, Marseille, France