Use Of Borane Research Articles

Toward metal- and catalyst-free Reactions: Deciphering the substituent and external electric field effects on the Diels-Alder reaction between ethylene and nitrosoethylene

The substituents on the diene and/or dienophile can contribute to the decrease or increase of this energy. However, there are other approaches to catalyze chemical reactions, particularly Diels-Alder reactions, for example, the application of an electric field along the reaction axis. The existence of an external electric field (EEF), properly oriented, has the potential to further stabilize or destabilize these electron density contributors and thus influence the energy. The goal of this study was to compare the activation energies of the Diels-Alder reaction between ethylene and nitrosoethylene, using an electric field, Lewis acid (BH3) as catalysts, and the influence of substituents. All calculations were performed with Gaussian09 software. The compounds were fully optimized using the restricted Hartree-Fock method with the basis set 6-31G, and single-point energies were determined with the MP3 method and basis set 6-31G. The effects of EEFs were studied using the “Field = M ± N” keyword with F values (F=±0.125 au and ± 0.080 au) along the preferred axis. The lowest activation barrier is encountered when the electric field is applied, followed by the use of borane as the Lewis acid.

Anti-Markovnikov Hydrogermylation of Alkenes via Lewis Acid Catalysis

AbstractThe direct hydrogermylation of alkenes under Lewis acid catalysis is reported. The use of borane B(C6F5)3 as a catalyst allows for a mild, metal-free hydrogermylation of alkenes and concomitant reduction of ketones and aldehydes. Regardless of electronic biases, anti-Markovnikov hydrogermylation is observed in high yields. Moreover, the process is scalable and proceeds under mild conditions at room temperature.

Triarylborane Catalyzed Carbene Transfer Reactions Using Diazo Precursors.

Reactive carbenes generated from diazo compounds are key intermediates for a range of organic reactions to afford synthetically useful organic compounds. The majority of these reactions have been carried out using transition metal catalysts. However, the formation of carbene intermediates using main group elements has not been widely investigated for synthetic purposes. Recent studies have demonstrated that triarylboranes can be used for the in situ generation of reactive carbene intermediates in both stoichiometric and catalytic reactions. These new reactivities of triarylboranes have gained significant attention in synthetic chemistry particularly in catalytic studies. The range of organic compounds that have been synthesized through these reactions are important as pharmaceuticals or agrochemicals. In this perspective, we highlight the recent progress and ongoing challenges of carbene transfer reactions generated from their corresponding diazo precursors using triarylboranes as catalysts. We also highlight the stoichiometric use of triarylboranes in which the boranes not only activate the diazo functionality to afford a carbene intermediate but also actively participate in the reactions as a reagent. The different mechanisms for activation and carbene transfer are described along with the mechanistic and computational studies that have aided the elucidation of these reaction pathways. Potential opportunities for the use of boranes as a catalyst toward different carbene transfer reactions and their future prospects are discussed.

Incorporation of small BN domains in graphene during CVD using methane, boric acid and nitrogen gas

Chemical doping of graphene with small boron nitride (BN) domains has been shown to be an effective way of permanently modulating the electronic properties in graphene. Herein we show a facile method of growing large area graphene doped with small BN domains on copper foils using a single step CVD route with methane, boric acid powder and nitrogen gas as the carbon, boron and nitrogen sources respectively. This facile and safe process avoids the use of boranes and ammonia. Optical microscopy confirmed that continuous films were grown and Raman spectroscopy confirmed changes in the electronic structure of the grown BN doped graphene. Using XPS studies we find that both B and N can be substituted into the graphene structure in the form of small BN domains to give a B-N-C system. A novel structure for the BN doped graphene is proposed.

Synthesis and use of borane and platinum(II) complexes of 3-diphenylphosphino-1- phenylphospholane (LuPhos)

3-Diphenylphosphinoyl-1-phenylphospholane 1-oxide (2) obtained by the Michael addition of diphenylphosphine oxide to the double-bond of 1-phenyl-2-phospholene 1-oxide (1) was subjected to double deoxygenation to afford the corresponding bisphosphine (3, LuPhos) that was converted to bis(phosphine borane) 4 and to cis chelate platinum(II) complex 6. A mixed phosphine oxide–phosphine borane 5 was also prepared. Stereostructures of the bidentate P-ligand 3 and the ring platinum(II) complex (6) were evaluated by quantum chemical calculations. Complex 6 used as a catalyst showed modest activity, but unusual regioselectivity in the hydroformylation of styrene and its 4-substituted analogues. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 22:730–736, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/hc.20741

Production of hydrogen from reactions of methane with boranes

The reactions of methane with different hydrides have been investigated using quantum chemical calculations (MP2 and CCSD(T) methods with the aug-cc-pVnZ one-electron functions extrapolated to the basis set limits). The hydrides of the elements of the second and third row, and also GaH(3), with an electronegativity smaller than the value of hydrogen (LiH, Li(2)H(2), BeH(2), NaH, MgH(2), BH(3), AlH(3), B(2)H(6), Al(2)H(6), SiH(4), PH(4) and GaH(3)) have been considered. Reactions of CH(4) with either BH(3) or LiH are characterized by the lowest energy barriers. Reactions using the known methylated derivatives of boranes with methane follow a similar mechanism. Calculated results strongly suggest the possible use of boranes as reagents in the reactions with methane to produce molecular hydrogen.

Influence of chemical vapor generation conditions on spectroscopic and analytical characteristics of a hyphenated CVG-ICP system

Excitation conditions of inductively coupled plasma hyphenated with chemical vapor generation with the use of borane reducing agents (NaBH4, C(CH3)3NH2–BH3 and (CH3)2NH–BH3) and acids (HCl and CH3COOH) were investigated. The electron number density, the Mg II/Mg I intensity ratio as well as the Ar, B, Bi, Sb and H excitation temperatures were measured at various concentrations of the reductants and acids. Some analytical figures of merit were also determined. The plasma parameters were affected if NaBH4 was applied. Influence of other borane reductants was not so significant. Hydrogen produced due to chemical vapor generation was responsible for changes in the ICP characteristics, while a role of other products transported simultaneously to plasma was negligible. The Ar, B, Bi and Sb excitation temperatures were independent or slightly dependent on chemical vapor generation conditions. The electron number density increased with NaBH4 concentration, from 0.7 × 1015 cm−3 for “dry” argon plasma to 1.5 × 1015 cm−3 while the Mg II/Mg I intensity ratio varied from 5 to 11. At low concentrations of the reductants and acids, the plasma was not in robust conditions. If the NaBH4 was the reductant, the H temperature varied more significantly, from 3100 to 2100 K.

ChemInform Abstract: The Use of Borane—Amine Adducts as Versatile Palladium‐Catalyzed Hydrogen‐Transfer Reagents in Methanol.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

The use of borane–amine adducts as versatile palladium-catalyzed hydrogen-transfer reagents in methanol

The scope of borane–amine adducts as reducing agents is broadened through palladium-catalyzed methanolysis capable of reducing a wide variety of functional groups. Hence, borane mediated reduction of a benzamide followed by a tandem methanolysis/hydrogenolysis of the resulting borane–benzylamine adduct allows chemoselective removal of an N-benzoyl in the presence of an O-benzoyl.

Selective reductions in the sphere of organophosphorus compounds

AbstractRecent results on the selective reduction of cyclic vinylphosphine oxides and vinylphosphinates, as well as their refunctionalization by the use of borane, are summarized. The selective reduction of the phosphorus moiety of unsaturated phosphonates, phosphinates, and phosphine oxides is also discussed. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:161–167, 2001

Reduction of Carboxylic Acids with Sodium Borohydride and an Electrophile

Our goal was to develop the new reduction conditions into a procedure applicable to the first-year organic chemistry laboratory, where reduction of the carboxylic acid group has remained an obstacle, notwithstanding the use of borane or LiAlH4 (2) on the microscale. The NaBH4 method with either electrophile can be modified to any scale; in our hands, the use of I2 as the electrophile performed better at the semimicro scale than the H2SO4 method.

Use of borane as reducing agent in sequence analysis of peptides by gas chromatography-mass spectrometry

The properties of borane as a reducing agent for N-acylated peptides, as compared to the known lithium aluminium deuteride procedure have been investigated The resulting polyamino-alcoholds are converted into the corresponding trimethylsilyl ethers and submitted to capillary gas chromatography. With borane the esterification of carboxy groups is not required, reduction proceeds very fast and work-up of the reaction mixture is simple. Correspondingly complete derivatization is caried out in a significantly shorter time than with lithium aluminum deuteride. In addition, fewer side-products are formed, even if a very large excess of borane is used. No problems arise with labile peptides, and the yields are high enough to allow derivatization, separation and identification of peptides in amounts as low as 200 pmoles.The separation of the polyamino-alcohols by capillary gas chromatography was demonstrated, and proved to be superior to the packed columns used hitherto.