- Boric acid as a precatalyst for BH3-catalyzed hydroboration
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We report that boric acid, BO3H3, is a good precatalyst for the BH3-catalyzed hydroboration of esters using pinacolborane as a borylation agent. Using microwave irradiation as an energy source, we demonstrated that a dozen esters were converted into the c
- Fontaine, Frédéric-Georges,Légaré Lavergne, Julien,To, Hoang-Minh
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p. 31941 - 31949
(2021/12/01)
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- Sodium Aminodiboranate, a New Reagent for Chemoselective Reduction of Aldehydes and Ketones to Alcohols
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Sodium aminodiboranate (NaNH 2(BH 3) 2, NaADBH) is a new member of the old borane family, which exhibits superior performance in chemoselective reduction. Experimental results show that NaADBH can rapidly reduce aldehydes and ketones to the corresponding alcohols in high efficiency and selectivity under mild conditions. There are little steric and electronic effects on this reduction.
- Wang, Jin,Guo, Yu,Li, Shouhu,Chen, Xuenian
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supporting information
p. 1104 - 1108
(2021/05/25)
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- Ammonia borane as a metal free reductant for ketones and aldehydes: A mechanistic study
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Without a catalyst ketones and aldehydes were reacted in THF with ammonia borane (AB) to proceed hydroboration forming alkyl borates. Mechanistic studies revealed that dissociation of ammonia from AB occurred before the hydroboration step. When methanol was used as the solvent, metal free methanolysis of AB would take place with the ketone/aldehyde being directly hydrogenated by the MeOH·BH3 complex.
- Yang, Xianghua,Fox, Thomas,Berke, Heinz
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experimental part
p. 7121 - 7127
(2011/10/05)
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- Copper-catalyzed trifluoromethylation of aryl iodides with potassium (trifluoromethyl)trimethoxyborate
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Potassium (trifluoromethyl)trimethoxyborate is introduced as a new source of CF3 nucleophiles in copper-catalyzed trifluoromethylation reactions. The crystalline salt is stable on storage, easy to handle, and can be obtained in near-quantitative yields simply by mixing B(OMe)3, CF3SiMe3, and KF. The trifluoromethylation reagent allows the conversion of various aryl iodides into the corresponding benzotrifluorides in high yields under mild, base-free conditions in the presence of catalytic quantities of a CuI/1,10-phenanthroline complex.
- Knauber, Thomas,Arikan, Fatih,Roeschenthaler, Gerd-Volker,Goossen, Lukas J.
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scheme or table
p. 2689 - 2697
(2011/04/15)
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- Molecular addition compounds. 15. Synthesis, hydroboration, and reduction studies of new, highly reactive tert-butyldialkylamine-borane adducts
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Two series of tert-butyldialkylamines have been prepared and examined for borane complexation. The complexing ability of each amine in the two series examined decreases in the order shown. First series: t- BuN(CH2CH2)2O 1a > t-BuNEt2 1b > t-BuNPr(n)21c > t-BuN(CH2CH2OMe)2 1d >> t-BuNBu(i)2 1e. Second series: t-BuNBu(i)Me 2a > t-BuNPr(i)Me 2b > t- BuNBu(i)Et 2c > t-BuNBu(i)Pr(n) 2d >>t-BuNPr(i)Et 2e. The reactivity of the corresponding borane adducts toward 1-octene increases in the reverse order. The following amines form highly reactive liquid borane adducts hydroborating 1-octene in tetrahydrofuran at room temperature in less than 1 h: t- BuN(CH2CH2OMe)2, t-BuNBu(i)Et, and t-BuNPr(i)Me. The limit of borane complexation among the amines examined is reached for t-BuNBu(i)2 exchanging borane neither with BMS nor with BH3-THF. Among the various borane adducts prepared, the more promising borane adducts, t-Bu(CH3OCH2CH2)2N-BH3 (7), t-BuMePr(i)N-BH3 (8), and t-BuEtBu(i)N-BH3 (9), were selected for complete hydroboration and reduction studies. Hydroboration studies with the new, highly reactive trialkylamine-borane adducts 7-9 and representative olefins, such as 1-hexene, styrene, β-pinene, cyclopentene, norbornene, cyclohexene, 2-methyl-2-butene, α-pinene, and 2,3-dimethyl-2-butene, in tetrahydrofuran, dioxane, tert-butyl methyl ether, n-pentane, and dichloromethane, at room temperature (22 ± 3°C) were carried out. The reactions are faster in dioxane, requiring 1-2 h for the hydroboration of simple, unhindered olefins to the trialkylborane stage. Moderately hindered olefins, such as cyclohexene and 2-methyl-2-butene, give the corresponding dialkylboranes rapidly, with further slow hydroboration. However, the more hindered olefins, α-pinene and 2,3-dimethyl-2-butene, give stable monoalkylboranes very rapidly, with further hydroboration proceeding relatively slowly. The hydroborations can also be carried out conveniently in other solvents, such as THF, tert-butyl methyl ether, and n-pentane. A significant rate retardation is observed in dichloromethane. Regioselectivity studies of 1-hexene and styrene using these amine-borane adducts show selectivities similar to that of BH3-THF. The rates and stoichiometry of the reaction of t-BuMePr(i)N-BH3 in tetrahydrofuran with selected organic compounds containing representative functional groups were also examined at room temperature. The reductions of esters, amides, and nitriles, which exhibit a sluggish reaction at room temperature, proceed readily under reflux conditions in tetrahydrofuran and dioxane and without solvent (at 85-90°C). The carrier amines can be recovered by simple acid-base manipulations in good yield and readily recycled to make the borane adducts.
- Brown, Herbert C.,Kanth, Josyula V. B.,Dalvi, Pramod V.,Zaidlewicz, Marek
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p. 6263 - 6274
(2007/10/03)
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- P-H bond activation of primary phosphine-boranes: Access to α-hydroxy and α,α′-dihydroxyphosphine-borane adducts by uncatalyzed hydrophosphination of carbonyl derivatives
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Primary P-phenyl and P-methyl phosphine-boranes 1 and 2 are prepared by complexation of the free phosphines with BH3 · SMe2. They are stable and can be purified by distillation. Under basic conditions, they lead selectively to secondary alkylphosphine-boranes and under neutral conditions to the corresponding mono- and bis-hydroxyphosphine-boranes 5 and 6. All these new compounds are purified by chromatography on silica gel. A competitive hydroboration induced by the decomplexation of BH3 is observed as a minor process. Conditions for the decomplexation of phosphine-borane adducts are presented.
- Bourumeau, Karine,Gaumont, Annie-Claude,Denis, Jean-Marc
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p. 205 - 213
(2007/10/03)
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