2467-18-7Relevant articles and documents
Boric acid as a precatalyst for BH3-catalyzed hydroboration
Fontaine, Frédéric-Georges,Légaré Lavergne, Julien,To, Hoang-Minh
, p. 31941 - 31949 (2021/12/01)
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
Copper-catalyzed trifluoromethylation of aryl iodides with potassium (trifluoromethyl)trimethoxyborate
Knauber, Thomas,Arikan, Fatih,Roeschenthaler, Gerd-Volker,Goossen, Lukas J.
scheme or table, p. 2689 - 2697 (2011/04/15)
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.
Molecular addition compounds. 15. Synthesis, hydroboration, and reduction studies of new, highly reactive tert-butyldialkylamine-borane adducts
Brown, Herbert C.,Kanth, Josyula V. B.,Dalvi, Pramod V.,Zaidlewicz, Marek
, p. 6263 - 6274 (2007/10/03)
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.
