5419-55-6Relevant articles and documents
Addition compounds of alkali-metal hydrides. 23. Preparation of potassium triisopropoxyborohydride in improved purity
Brown, Herbert C.,Nazer, Behrooz,Sikorski, James A.
, p. 634 - 637 (1983)
Commercial potassium triisopropoxyborohydride, K(i-PrO)3BH, or the usual material prepared at 25 °C from potassium hydride and triisopropoxyborane in tetrahydrofuran contains a significant impurity, detectable in the 11B NMR spectrum. This impurity, probably potassium tetraisopropoxyborohydride, significantly decreases the yield when the reagent is used to hydride thexylmonoalkylchloroboranes, ThxBR1Cl, for the synthesis of mixed thexyldialkylboranes. This impurity can be removed by refluxing a THF solution of the impure potassium triisopropoxyborohydride over potassium hydride. Alternatively, the reaction of triisopropoxyborane with excess KH in refluxing THF gives a product essentially free of the impurity. Storage of the solution KIPBH over a small excess of potassium hydride (～10%) maintains the product essentially free of the impurity. Use of this material permits the preparation of essentially quantitative yields of the desired mixed thexyldialkylboranes, ThxBR1R2, via the hydridation of the intermediate ThxBR1Cl in the presence of a second olefin.
Base-Catalyzed Aryl-B(OH)2 Protodeboronation Revisited: From Concerted Proton Transfer to Liberation of a Transient Aryl Anion
Cox, Paul A.,Reid, Marc,Leach, Andrew G.,Campbell, Andrew D.,King, Edward J.,Lloyd-Jones, Guy C.
supporting information, p. 13156 - 13165 (2017/09/26)
Pioneering studies by Kuivila, published more than 50 years ago, suggested ipso protonation of the boronate as the mechanism for base-catalyzed protodeboronation of arylboronic acids. However, the study was limited to UV spectrophotometric analysis under acidic conditions, and the aqueous association constants (Ka) were estimated. By means of NMR, stopped-flow IR, and quenched-flow techniques, the kinetics of base-catalyzed protodeboronation of 30 different arylboronic acids has now been determined at pH > 13 in aqueous dioxane at 70 °C. Included in the study are all 20 isomers of C6HnF(5-n)B(OH)2 with half-lives spanning 9 orders of magnitude: a and Sδ values, kinetic isotope effects (2H, 10B, 13C), linear free-energy relationships, and density functional theory calculations, we have identified a mechanistic regime involving unimolecular heterolysis of the boronate competing with concerted ipso protonation/C-B cleavage. The relative Lewis acidities of arylboronic acids do not correlate with their protodeboronation rates, especially when ortho substituents are present. Notably, 3,5-dinitrophenylboronic acid is orders of magnitude more stable than tetra-and pentafluorophenylboronic acids but has a similar pKa.
Synthesis of 3-(5-methylthiophen-2-yl)coumarins and their photochromic dihetarylethene derivatives
Bochkov, Andrei Y.,Krayushkin, Mikhail M.,Yarovenko, Vladimir N.,Barachevsky, Valery A.,Beletskaya, Irina P.,Traven, Valery F.
, p. 891 - 898 (2013/08/23)
Novel unsymmetrical di(thienyl)maleic acid anhydride, including coumarin moiety, has been designed and synthesized. Its photochromism study and fatigue resistance estimation are reported. Microwave-assisted procedure has been successfully used for synthesis of 3-(5-methylthiophen-2-yl)coumarins.
A new method for the chemoselective reduction of aldehydes and ketones using boron tri-isopropoxide, B(OiPr)3: Comparison with boron tri-ethoxide, B(OEt)3
Uysal, Burcu,Oksal, Birsen S.
body text, p. 681 - 685 (2012/06/18)
A chemoselective Meerwein-Ponndorf-Verley reduction process of various aliphatic and allylic α,β-unsaturated aldehydes and ketones is described. This chemoselective reduction is catalysed by boron triisopropoxide B(Oi Pr)3. Kinetics of reduction of aldehydes and ketones to corresponding alcohols were also examined and rate constant of each carbonyl compounds were measured. Rate constant and reduction yield of each carbonyl compounds in the presence of B(Oi Pr)3 were compared with those in the presence of B(OEt)3. The alcohols that are the reduction product were analysed by GC-MS. The rate constants and alcohol yields were found to be higher with B(OEt)3 than with B(Oi Pr) 3. The mechanism proposed involves a six-membered transition state in which both the alcohol and the carbonyl are coordinated to the same boron centre of a boron alkoxide catalyst. Indian Academy of Sciences.
In vitro antibacterial and antifungal activities of some sulfur-nitrogen-oxygen and oxygen-nitrogen-oxygen donor bifunctional tridentate schiff bases and their boron(III) complexes
Yadav, Sunita,Swami, Monika,Singh
experimental part, p. 394 - 401 (2010/07/03)
Antimicrobial properties of sulfur, nitrogen, and oxygen bonded organoboron (III) complexes with biologically potent ligands viz., 2-hydroxy-N-phenyl benzamide hydrazine carboxamide(HO∩N∩OH), 2-hydroxy-N-phenyl benzamide hydrazine carbothioamide (HO∩N∩∩SH), and 2-hydroxy-N-phenyl benzamide hydrazine carbodithioic acid (HO∩N∩SH), have been studied. The unimolar and bimolar reactions of triisopropoxy borane with dibasic tridentate ligands resulted in the formation of colored solids, which have been characterized by elemental analysis, molecular weight determinations, and conductance measurements. The UV, IR, and NMR (1H, 13C, and 11B) spectral studies indicate a tetra-coordinated geometry for the resulting complexes. The ligands and their complexes have been screened for their fungicidal and bactericidal activities, and the results indicate that they exhibit significant antimicrobial properties. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.
Effect of the secondary reduction on the enantioselectivity and function of additives in the chiral oxazaborolidine-catalyzed asymmetric borane reduction of ketones
Liu, Han,Du, Da-Ming,Xu, Jiaxi
, p. 1067 - 1074 (2007/10/03)
The secondary reduction in the direct and oxazaborolidine-catalyzed asymmetric borane reduction of ketones was investigated by the use of GC/MS tracing titration and control experiments. The results indicate that the secondary reduction affects the enantioselectivity only in noncoordinated solvents at low temperature and not under the usual catalytic reduction conditions because the intermediate alkoxyborane is unstable and quickly converts to borane and dialkoxyborane. The function of an alcohol additive in the asymmetric borane reduction of ketones is to consume excess borane in the reduction system thus inhibiting noncatalytic reduction, which leads to increased enantioselectivity in the catalytic reduction.
Application of Mechanochemical Catalysis to the Synthesis of Boric Acid Esters
Molchanov,Goidin,Golovin,Zolotovskaya,Bogdanov,Volodin
, p. 536 - 541 (2008/10/08)
The syntheses of triisopropyl borate and other boric acid esters under conditions of mechanochemical activation (MCA) with the use of zeolite catalysts were presented. The proposed method showed short synthesis times, low energy consumption, higher yields of target products, and the absence of byproducts. The mechanism of the catalytic esterification of boric acid under conditions of MCA was described. The conversion was no > 30%. The introduction of zeolites into the reaction zone increased the degree of conversion because of water removal from the reaction medium. Lower conversions of 2-butanol were related to its high viscosity, as a result of which the intensity of MCA was considerably decreased.
Convergent synthesis of alpha -aryl- beta -ketonitriles
-
, (2008/06/13)
The present invention relates to processes for the production of alpha -aryl- beta -ketonitriles, which serve as synthetic intermediates in the preparation of a series of biologically important molecules such as corticotropin releasing factor (CRF) receptor antagonists.
Practical and efficient procedure for the in situ preparation of B-alkoxyoxazaborolidines. Enantioselective reduction of prochiral ketones
Ponzo, Viviana L.,Kaufman, Teodoro S.
, p. 495 - 496 (2007/10/03)
A new method for the in situ elaboration of B-alkoxyoxazaborolidines is presented. Their use in the enantioselective reduction of prochiral aromatic ketones provides excellent chemical and optical yields of chiral alcohols.
Beitraege zur Chemie des bors, 226: Funktionalisierung von Alkinylboranen-Umsetzung mit Nucleophilen
Feulner, Herta,Metzler, Nils,Noeth, Heinrich
, p. 51 - 62 (2007/10/02)
The synthesis of alkynylboranes RR'B-CC-R" 1-3 and their reactions with various nucleophiles are described (R, R' = Me2N, Cl, alkyl; R" = Me, Ph).Although these compounds can be looked upon as inorganic Michael systems, nucleophiles such as alcohols, amines, amides and various carbon nucleophiles attack exclusively at the boron atom (analogous to a 1,2- attack).Thus, a nonvenient means of functionalization of alkynylboranes at the boron atom with preservation of the B-CC moiety is described, and alkynylboranes with R,R' = Me2N, N(H)iPr, pyr, OiPr, Me, Mes, CC-SiMe3 were obtained in good yield and characterized by spectroscopic methods.The pathway for the reaction of (Me2N)2B-CC-Ph with carbon nucleophiles to tris(alkyl)boranes has been elucidated.The implications both for the electronic properties and the chemical reactivity of alkynylboranes are discussed.Keywords: Alkynylboranes, Nucleophilic attack, Organoboron compounds, Inorganic Michael systems; Boron; Alkyne
