Triphenylphosphine-borane

The procedure described for the preparation of ethylenediamine-bisborane is general for the synthesis of amine-boranes and of borane adducts of other electron donors in which elements such as phosphorus and sulfur serve as the donor atom. In addition to the procedure used here for triphenylphosphine-borane, borane adducts of phosphines have been prepared by Analytical reagent grade (Mallinckrodt). 

A suspension prepared from 4.25 g. of 95% sodium borohydride (0.11 mole) and 150 ml. of tetrahydrofuran is cooled in an ice-water bath and stirred while a solution containing 17 ml. (0.13 mole) of boron trifluoride-diethylether in 60 ml. of tetrahydrofuran is added dropwise over a period of 45 minutes. Thirty grams (0.11 mole) of triphenylphosphine is dissolved in 130 ml. of tetrahydrofuran, and this solution is added through a dropping funnel to the cooled suspension (1 hour). The mixture is allowed to warm to room temperature. Solids are collected by filtration, and the crude product is recovered by evaporation of the solvent from the filtrate in vacuo. Yield is 32 g. (100% theory). 

sample of crude product is washed with 150 ml. of cool distilled water. The white crystalline product is collected by filtration, washed with water, and dried in vacuo. Yield is 27.6 g. (94.2% theory). Anal. Calcd. for CigHigPB (276.13) C, 78.29 H, 6.57. Found C, 78.27 H, 6.56 m.p. 184.5-187°C. 

A characteristic feature of this compound is the high resistance to hydrolysis of boron-bonded hydrogens shown, in part, by the fact that the compound can be recovered unchanged from 

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Cognate preparation. 3,4-Dimethoxybenzaldehyde 2.4-dudtrophenylhydror zone (use of bis(triphenylphosphine)copper(i) tetrahydroborate)50 3,4-Dimethoxybenzoyl chloride (1.14g, 5.7 mmol) in acetone (100 ml) is treated with triphenylphosphine (3.04 g, 11.6 mmol). To this solution at room temperature, bis(triphenylphosphine)copper(i) tetrahydroborate (3.47 g, 5.8 mmol) (Section 4.2.49, p. 449) is added and the reaction mixture stirred for 45 minutes. The white precipitate of triphenylphosphine copper chloride (4.9 g, 5.5 mmol) is removed by filtration and the filtrate evaporated to dryness. The residue is extracted with ether (the ether-insoluble residue is shown to be triphenylphosphine borane). The ether is removed, the residue... 

C. 4-(3-Cyclohexenyl)-2-phenylthio-1-butene. To the above solution of the borane derivative, 0.809 g (0.700 mmol) of tetrakis(triphenylphosphine)palladium(0) (Note 9), 1.47 g (5.60 mmol) of triphenylphosphine (Note 10), 35 mL of 3 M potassium phosphate in water (Note 11), and finally 15.1 g (70.0 mmol) of 1-bromo-1-phenylthioethene are added and the resulting mixture is heated at reflux for 3 hr with stirring. The light brown solution is cooled to room temperature and treated with 6.4 g... 

Common reducing agents are hydrogen in the presence of metallic or complex catalysts (e.g. Ni, Pd, Pt, Ru, Rh), hydrides (e.g. alanes, boranes, LiAlH4, NaBHJ, reducing metals (e.g. Li, Na, Mg, Ca, Zn), and low-valent compounds of nitrogen (e.g. NjH NjHJ, phosphorus (e.g. triethyl phosphite, triphenylphosphine), and sulfur (e.g. H0-CH2-S02Na = SFS, sodium dithionite = Na SjO. ... 

Hydroboration.1 The usual hydroboration reagents, BH3THF and BH3-S(CH3)2, are sensitive to oxygen and moisture and require special handling. 1 he complexes of BH3 and phosphorus compounds are generally stable, but much less reactive. The complex of BH3 and triphenylphosphine, m.p. 189°, can be used for hydroboration if activated by addition of methyl iodide (to form a phosphonium iodide) or sulfur (to form a triphenylphosphine sulfoxide). The complex of borane and triphenyl phosphite does not require activation and hydroborates alkenes in a reasonable time in refluxing DME or THF. Trialkyl phosphite complexes are not useful. 

Diethyl(3-pyridyl)borane (3.38 g, 23 mmol) from Aldrich Chemical Co. Ltd. was added to a stirred solution of 3p-acetoxyandrosta-5,16-dien-17-yl trifluoromethanesulphonate (6.94 g, 15 mmol) in THF (75 ml) containing bis(triphenylphosphine)palladium(II) chloride (0.105 g, 0.15 mmol). An aqueous solution of sodium carbonate (2 M, 30 ml) was then added and the mixture heated, with stirring, by an oil bath at 80°C for 1 h, and allowed to cool. The mixture was partitioned between diethyl ether and water, the ether phase was dried (Na2C03), filtered through a short plug of silica, and concentrated. Chromatography, on elution with light petroleum-diethyl ether (2 1), afforded the 3 5-acetoxy-17-(3-pyridyl)androsta-5,16-diene (4.95 g, 84%) which crystallised from hexane, m.p. 144-145°C. 

The extremely broad functional group tolerance of the Pd-catalysed N-de protection of Aloe groups was a crucial design feature in a synthesis of the epoxy-quinol core of the Manumycin family of antitumour antibiotics [Scheme 8,80].195 Note the convenient generation of the Pd(0) catalyst in situ from reaction of dichlorobis(triphenylphosphine)palladium(II) with tributylstannane. The use of sodium borohydride and borane dime thy lamine complex is illustrated in Schemes 8.81193 and 8.82194 respectively. 

Vinylic ethers (44) can be synthesized in high yields by the cross-coupling of aryl or benzyl halides with tris(2-ethoxyvinyl)borane (4S) in the presence of 1 molej% of a palladium compound such as tetrakis(triphenylphosphine)palladium and a base (Eq. 108) Since vinylic ethers (44) thus obtained can readily be hydrolyzed to aldehydes, this reaction provides a convenient procedure for converting aryl or benzylic halides into the corresponding aldehydes with two more carbon atoms. 

BCjHg, Borane, trimethyl-, 27 339 BClF4lrN2N2P2C H , Iridium(III), chloro-(dinitrogen)hydrido[tetrafluoroborato-(1 - )]bis(triphenylphosphine)-, 26 119 BClF4lrOP2C37H3i, Iridium(III), carbonyl-chlorohydrido[tetrafluoroborato( I — ))-bis(triphenylphosphine)-, 26 117... 

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