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Borane–tetrahydrofuran
Borane–tetrahydrofuran is a dipolar bond charge-transfer complex composed of borane and tetrahydrofuran (THF). These solutions are used for reductions and hydroboration, reactions that are useful in synthesis of organic compounds.Marek Zaidlewicz, Herbert C. Brown, Santhosh F. Neelamkavil, "Borane–Tetrahydrofuran" Encyclopedia of Reagents for Organic Synthesis, 2008 John Wiley & Sons. Preparation and uses The complex is commercially available but can also be generated by the dissolution of diborane in THF. A practical route to this is the oxidation of sodium borohydride with iodine in THF. The complex can reduce carboxylic acids to alcohols and is a common route for the reduction of amino acids to amino alcohols (e.g. valinol). It adds across alkenes to give organoboron compounds that are useful intermediates. The following organoboron reagents are prepared from borane-THF: 9-borabicyclo .3.1onane, Alpine borane, diisopinocampheylborane. It is also used as a source of bo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dipolar Bond
In coordination chemistry, a coordinate covalent bond, also known as a dative bond, dipolar bond, or coordinate bond is a kind of two-center, two-electron covalent bond in which the two electrons derive from the same atom. The bonding of metal ions to ligands involves this kind of interaction. This type of interaction is central to Lewis acid–base theory. Coordinate bonds are commonly found in coordination compounds. Examples Coordinate covalent bonding is ubiquitous. In all metal aquo-complexes (H2O)''n'''m''+, the bonding between water and the metal cation is described as a coordinate covalent bond. Metal-ligand interactions in most organometallic compounds and most coordination compounds are described similarly. The term ''dipolar bond'' is used in organic chemistry for compounds such as amine oxides for which the electronic structure can be described in terms of the basic amine donating two electrons to an oxygen atom. : → O The arrow → indicates that both ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Organoboron Compound
Organoborane or organoboron compounds are chemical compounds of boron and carbon that are Organic compound, organic derivatives of BH3, for example trialkyl boranes. Organoboron chemistry or organoborane chemistry is the chemistry of these compounds. Organoboron compounds are important reagents in organic chemistry enabling many chemical transformations, the most important one called hydroboration. Reactions of organoborates and boranes involve the transfer of a nucleophilic group attached to boron to an electrophilic center either inter- or intramolecularly. α,β-Unsaturated borates, as well as borates with a leaving group at the α position, are highly susceptible to intramolecular 1,2-migration of a group from boron to the electrophilic α position. Oxidation or protonolysis of the resulting organoboranes may generate a variety of organic products, including alcohols, carbonyl compounds, alkenes, and halides. Properties of the B-C bond The C-B bond has low polarity (the diffe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Borane Tert-butylamine
Borane ''tert''-butylamine is an amine borane complex derived from ''tert''-butylamine and borane. It is a colorless solid. The compound is prepared by the reaction of tert-butylammonium chloride and sodium borohydride:Girolami, G. S.; Rauchfuss, T. B. and Angelici, R. J., Synthesis and Technique in Inorganic Chemistry, University Science Books: Mill Valley, CA, 1999. :''t''-BuNH3Cl + NaBH4 → ''t''-BuNH2BH3 + H2 + NaCl In organic synthesis, borane ''tert-''butylamine can be used for selective reduction of certain functional groups including aldehydes, ketones, oximes, and imines. In photographic processing Photographic processing or photographic development is the chemical means by which photographic film or paper is treated after photographic exposure to produce a negative or positive image. Photographic processing transforms the latent image in ..., it is used in the E-4 process, as "chemical enlighting" step in the processing of the film. See also * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Borane Dimethylsulfide
Borane dimethylsulfide (BMS) is a complexed borane reagent that is used for hydroborations and reductions. The advantages of BMS over other borane reagents, such as borane-tetrahydrofuran, are its increased stability and higher solubility. BMS is commercially available at much higher concentrations than its tetrahydrofuran counterpart (10 M) and does not require sodium borohydride as a stabilizer, which could result in undesired side reactions. In contrast, borane·THF requires sodium borohydride to inhibit reduction of THF to tributyl borate. BMS is soluble in most aprotic solvents. Preparation and structure Although usually purchased, BMS can be prepared by absorbing diborane into dimethyl sulfide: :B2H6 + 2 SMe2 → 2 Me2SBH3 It can be purified by bulb to bulb vacuum transfer. Although a structure of BMS has not been determined crystallographically, (pentafluorophenyl)-borane dimethylsulfide (C6F5BH2SMe2), has been examined by X-ray crystallography. The boron center ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ammonia Borane
Ammonia borane (also systematically named amminetrihydridoboron), also called borazane, is the chemical compound with the formula H3NBH3. The colourless or white solid is the simplest molecular boron-nitrogen-hydride compound. It has attracted attention as a source of hydrogen fuel, but is otherwise primarily of academic interest. Synthesis Reaction of diborane with ammonia mainly gives the diammoniate salt 2B(NH3)2sup>+ (BH4)−. Ammonia borane is the main product when an adduct of borane is employed in place of diborane: :BH3(THF) + NH3 → BH3NH3 + THF Properties and structure The molecule adopts a structure similar to that of ethane, with which it is isoelectronic. The B−N distance is 1.58(2) Å. The B−H and N−H distances are 1.15 and 0.96 Å, respectively. Its similarity to ethane is tenuous since ammonia borane is a solid and ethane is a gas: their melting points differing by 284 °C. This difference is consistent with the highly polar natur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Air-free Technique
Air-free techniques refer to a range of manipulations in the chemistry laboratory for the handling of compounds that are air-sensitive. These techniques prevent the compounds from reacting with components of air, usually water and oxygen; less commonly carbon dioxide and nitrogen. A common theme among these techniques is the use of a fine (100–10−3 Torr) or high (10−3–10−6 Torr) vacuum to remove air, and the use of an inert gas: preferably argon, but often nitrogen. The two most common types of air-free technique involve the use of a glovebox and a Schlenk line, although some rigorous applications use a high-vacuum line. In both methods, glassware (often Schlenk tubes) are pre-dried in ovens prior to use. They may be flame-dried to remove adsorbed water. Prior to coming into an inert atmosphere, vessels are further dried by ''purge-and-refill'' — the vessel is subjected to a vacuum to remove gases and water, and then refilled with inert gas. This cycle is usually r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diisopinocampheylborane
Diisopinocampheylborane is an organoborane that is useful for asymmetric synthesis. This colourless solid is the precursor to a range of related reagents. The compound was reported in 1961 by Zweifel and Brown in a pioneering demonstration of asymmetric synthesis using boranes. The reagent is mainly used for the synthesis of chiral secondary alcohols. Preparation Diisopinocampheylborane was originally prepared by hydroboration of excess α-pinene with borane, but it is now more commonly generated from borane-methyl sulfide (BMS). The compound can be isolated as a solid. However, because it is quite sensitive to water and air, this reagent is often generated in situ and used as a solution. Diisopinocampheylborane is monomeric, in contrast to diborane and many of its less bulky analogues. Reactions Oxidation of diisopinocampheylborane with basic hydrogen peroxide gives isopincampheol. Methanolysis gives methoxydiisopinocampheylborane Hydroboration Because of the large size ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Alpine Borane
Alpine borane is the commercial name for an organoboron compound that is used in organic synthesis. It is a colorless liquid, although it is usually encountered as a solution. Preparation and reactions This reagent is generated by treating 9-BBN with α-pinene. This sterically crowded chiral trialkylborane can stereoselectively reduce aldehydes in what is known as the Midland Alpine borane reduction, or simply the Midland reduction. :C8H12B-pinanyl + RCDO → C8H12BOCHDR + (+)-''d''-pinene Hydrolysis of the resulting borinic ester affords the alcohol: :C8H12BOCHDR + H2O → C8H12BOH + HOCHDR It is also effective for the stereoselective reduction of certain acetylenic ketones. The reaction is proposed to involve formation of an adduct by coordination of the carbonyl oxygen to boron. Intramolecular hydride transfer from the pinane substituent to the carbonyl carbon ensues. Related reagents A range of alkyl-substituted borane are specialty reagents in organic synthesis. Two s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Valinol
Valinol is an organic compound named after, and commonly produced from, the amino acid valine. The compound is chiral and is produced almost exclusively as the S‑isomer (also designated as the L‑isomer), due to the abundant supply of S-valine. It is part of a broader class of amino alcohols. Synthesis Valinol can be generated by converting the carboxylic group of valine to an alcohol with a strong reducing agent such as lithium aluminium hydride, or with NaBH4 and I2 (forming the borane–tetrahydrofuran complex). In both cases the valinol produced can be subsequently purified by short path distillation. Reactions Valinol is mainly used to prepare chiral oxazolines, a process which can be achieved via a variety of methods. These oxazolines are principally used as ligands in asymmetric catalysis Enantioselective synthesis, also called asymmetric synthesis, is a form of chemical synthesis. It is defined by IUPAC as "a chemical reaction (or reaction sequence) in which ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Charge-transfer Complex
In chemistry, a charge-transfer (CT) complex or electron-donor-acceptor complex describes a type of supramolecular assembly of two or more molecules or ions. The assembly consists of two molecules that self-attract through electrostatic forces, i.e., one has at least partial negative charge and the partner has partial positive charge, referred to respectively as the electron acceptor and electron donor. In some cases, the degree of charge transfer is "complete", such that the CT complex can be classified as a salt. In other cases, the charge-transfer association is weak, and the interaction can be disrupted easily by polar solvents. Examples Electron donor-acceptor complexes A number of organic compounds form charge-transfer complex, which are often described as electron-donor-acceptor complexes (EDA complexes). Typical acceptors are nitrobenzenes or tetracyanoethylene. The strength of their interaction with electron donors correlates with the ionization potentials of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amino Alcohols
In organic chemistry, alkanolamines are organic compounds that contain both hydroxyl () and amino (, , and ) functional groups on an alkane backbone. The term alkanolamine is a broad class term that is sometimes used as a subclassification. Methanolamine.svg, methanolamine, an intermediate in the reaction of ammonia with formaldehyde Ethanolamine.png, Ethanolamine 2-amino-2-methyl-1-propanol.svg, 2-amino-2-methyl-1-propanol is a precursor to oxazolines valinol.svg, valinol is derived from the amino acid valine Sphingosine structure.svg, Sphingosine is a component of some cell membrane. 1-Aminoalcohols 1-Aminoalcohols are better known as hemiaminals. Methanolamine is the simplest member. 2-Aminoalcohols Key members: ethanolamine, dimethylethanolamine, ''N''-methylethanolamine, Aminomethyl propanol Two popular drugs, often called alkanolamine beta blockers, are members of this structural class: propranolol, pindolol. Isoetarine is yet another medicinally useful derivativ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
