Amines Borane-Tetrahydrofuran

Diborane [19287-45-7] the first hydroborating agent studied, reacts sluggishly with olefins in the gas phase (14,15). In the presence of weak Lewis bases, eg, ethers and sulfides, it undergoes rapid reaction at room temperature or even below 0°C (16—18). The catalytic effect of these compounds on the hydroboration reaction is attributed to the formation of monomeric borane complexes from the borane dimer, eg, borane-tetrahydrofuran [14044-65-6] (1) or borane—dimethyl sulfide [13292-87-0] (2) (19—21). Stronger complexes formed by amines react with olefins at elevated temperatures (22—24). 

Borane complexes are the most widely used commercial boron compounds, after sodium borobydride. Examples used in organic synthesis are amine borane complexes and borane complexes of tetrahydrofuran and dimethyl sulfide. 

Benzyl bromide, Molecular sieve, 2735 Benzyl chloride, Catalytic impurities, 2738 1,2-Bis(chloromethyl)benzene, 2946 Bis(2-cyanoethyl)amine, 2397 Bis(trimethylsilyl) peroxomonosulfate, 2602 Borane -tetrahydrofuran, 0138 Butylmagnesium chloride, 1641 Calcium acetylide, Methanol, 0585 Calcium chloride, 3923 Cerium, Water, 3961... 

Reduction of the nitro compounds (193 R = R = H, or R = Me, R = OH) with lithium aluminum hydride affords the corresponding saturated amine.556 Similar reduction of carboxamides with the general formula (194) affords the corresponding amines143,8n 313, 568,569. jn t,]ie Case of 194 (R = H, R = 6-OMe), reduction with borane tetrahydrofuranate is more satisfactory.312... 

Reduction of amides. Sodium borohydride combined with methanesulfonic acid in DMSO reduces amides to the corresponding amines in 60-90% isolated yield. I he system also reduces acids and esters to primary alcohols. These reductions have been conducted with lithium aluminum hydride and with borane-tetrahydrofurane (5,48),2 hut with somewhat different selectivities. This new reagent, however, appears to be less hazardous than the latter reagent. 

Borane-Amine Complexes or Borane Tetrahydrofuran. Deactivate by slow addition of a mixture of the appropriate solvent and butanol. Place in a separate labeled container for disposal by burning. Spray into furnace equipped with afterburner and scrubber.12 13... 

It results in the formation of the corresponding borazinyl-N-alkyl-amine-boranes [BH3(CH3)2N(CH2)3NBH]3 when the reaction is carried out with only 6 molar equivalents of the diamine. Aromatic diamines have also been used in this synthesis 103>. Borazines with N-organosilicon substituents have been obtained by reacting silicon-containing nitriles, for example, 4-cyano-2,2,6,6-tetramethyl-2,6-disilatetrahydropyrane, with NaBH4 and BF3 in tetrahydrofuran. 

Various procedures for the purification of specific amine-boranes have been reported.12 Ethylenediamine-bisborane can be purified conveniently by aqueous extraction to remove water-soluble impurities. The crude product obtained from the tetrahydrofuran solution is ground to a fine powder in a mortar and added in small portions, with stirring, to about 75 ml. of water which has been cooled in an ice-water bath. Foaming may occur during this treatment. The white crystalline solid which does not dissolve is collected by filtration through a coarse-fritted-glass funnel and washed several times with small portions of cold water (about 5°C.). The final wash filtrate should be neutral toward pH paper. The product is dried by... 

REDUCTION, REAGENTS Bis(N-methylpi-perazinyl)aluminum hydride. Borane-Di-methyl sulfide. Borane-Tetrahydrofurane. Borane-Pyridine. n-Butyllithium-Diisobu-tylaluminum hydride. Calcium-Amines. Diisobutylaluminum hydride. 8-Hydroxy-quinolinedihydroboronite. Lithium aluminum hydride. Lithium 9-boratabicy-clo[3.3.1]nonane. Lithium n-butyldiisopro-pylaluminum hydride. Lithium tri-j c-butylborohydride. Lithium triethylborohy-dride. Monochloroalane. Nickel boride. 2-Phenylbenzothiazoline. Potassium 9-(2,3-dimethyl-2-butoxy)-9-boratabicy-clo[3.3.1]nonane. Raney nickel. Sodium bis(2-methoxyethoxy)aluminum hydride. Sodium borohydride. Sodium borohy-dride-Nickel chloride. Sodium borohy-dride-Praeseodymium chloride. So-dium(dimethylamino)borohydride. Sodium hydrogen telluride. Thexyl chloroborane-Dimethyl sulfide. Tri-n-butylphosphine-Diphenyl disulfide. Tri-n-butyltin hydride. Zinc-l,2-Dibromoethane. Zinc borohydride. 

Amine-boranes are important boron-nitrogen compounds. They are prepared by various methods such as direct combination of amine and diborane,1,2 reaction of tetrahydroborates with ammonium salts,3 transamination of amine-boranes,4 or displacement of tetrahydrofuran from tetrahydrofuran-borane which is first prepared from boron trifluoride etherate and sodium tetrahydroborate,5 or by less convenient methods like reduction of an appropriate... 

M of ring substituted styrene or propenylbenzene in 30 ml tetrahydrofuran in V2L flask. Flush with N2 and add 33 ml 1 M borane in tetrahydrofuran (see procedure below for preparation). Stir one hour, add 3 ml water and 50 ml 3N NaOH, and then 215 ml 0.31 M fresh chloramine solution (prepared by treating dilute aqueous NH4OH with Na hypochlorite at 0° see BER 40,4586 (1907)). Keep at room temperature one hour, acidify with HCI, extract with ether, basify with NaOH and extract with ether and dry, evaporate in vacuum (or just basify and extract with ether and dry, evaporate in vacuum) to get the amine. 

A boron analog - sodium borohydride - was prepared by reaction of sodium hydride with trimethyl borate [84 or with sodium fluoroborate and hydrogen [55], and gives, on treatment with boron trifluoride or aluminum chloride, borane (diborane) [86. Borane is a strong Lewis acid and forms complexes with many Lewis bases. Some of them, such as complexes with dimethyl sulfide, trimethyl amine and others, are sufficiently stable to have been made commercially available. Some others should be handled with precautions. A spontaneous explosion of a molar solution of borane in tetrahydrofuran stored at less than 15° out of direct sunlight has been reported [87]. 

Opening of a bottle where some particles of lithium aluminum hydride were squeezed between the neck and the stopper caused a fire [68]. Lithium aluminum hydride must not be crushed in a porcelain mortar with a pestle. Fire and even explosion may result from contact of lithium aluminum hydride with small amounts of water or moisture. Sodium bis(2-methoxy-ethoxy)aluminum hydride (Vitride, Red-Al ) delivered in benzene or toluene solutions also may ignite in contact with water. Borane (diborane) ignites in contact with air and is therefore kept in solutions in tetrahydrofuran or in complexes with amines and sulfides. Powdered lithium borohydride may ignite in moist air. Sodium borohydride and sodium cyanoborohydride, on the other hand, are considered safe. ... 

High yields of amines have also been obtained by reduction of amides with an excess of magnesium aluminum hydride (yield 100%) [577], with lithium trimethoxyaluminohydride at 25° (yield 83%) [94] with sodium bis(2-methoxy-ethoxy)aluminum hydride at 80° (yield 84.5%) [544], with alane in tetra-hydrofuran at 0-25° (isolated yields 46-93%) [994, 1117], with sodium boro-hydride and triethoxyoxonium fluoroborates at room temperature (yields 81-94%) [1121], with sodium borohydride in the presence of acetic or trifluoroacetic acid on refluxing (yields 20-92.5%) [1118], with borane in tetrahydrofuran on refluxing (isolated yields 79-84%) [1119], with borane-dimethyl sulflde complex (5 mol) in tetrahydrofuran on refluxing (isolated yields 37-89%) [1064], and by electrolysis in dilute sulfuric acid at 5° using a lead cathode (yields 63-76%) [1120]. 

The hydroboration amination sequence in diglyme is a general procedure for the conversion of olefins to primary amines without rearrangement and with predictable stereochemistry.5 An alternative procedure, using tetrahydrofuran as solvent and either hydroxylamine-O-sulfonic acid or chloramine, is applicable with terminal olefins and relatively unhindered internal and alicyclic olefins.6 O-Mesitylenesulfonylhydroxylamine also gave desired amines in comparable yield.7 Alternative procedures for the hydroboration of olefins use commercially available solutions of di-borane in tetrahydrofuran8 or dimethylsulfide.9... 

Polymeric precursors have been developed which are stable at room temperature and when polymerized convert to ceramics in high yield. Such precursors may be synthesized by reaction of a vinylsilane, vinylmethylsilane, acetylene silane, or acetylene alkyl silane with a borane or a borane amine derivative The reactants are mixed in an inert atmosphere, either neat or in an aprotic solvent like acetonitrile, tetrahydrofuran, or a hydrocarbon, or in a mixture of such solvents. The reaction mixture is heated for 0.1 to 120 h at 90-170°C. The solvent, if any, is then removed. The polymer is pyrolyzed in argon or N2 at SOO-ISOO C for 1 h. BN and other ceramics such as B4C, or SipB QNs compounds can be made, where p, q, r, and s have various numerical values. To date, no measurements of the crystallographic form of the resultant BN compound have been made. Other precursors convertible to BN include poly (2-vinylpentaborane) oligomers. ... 

As for dihydro-1,3-oxazines, perhydro-1,3-oxazine methiodides (125) are ring-opened by reaction with sodium borohydride. The products obtained depend upon the conditions used thus, in anhydrous tetrahydrofuran tertiary amines and their borane derivatives are formed, but in ethanol or methanol transesterification occurs to give the corresponding ethyl or methyl ethers (Scheme 32) <90H(31)2079>. 

Conanine (la) readily yielded the diastereoisomeric borane complexes (2a) on reaction with borane in tetrahydrofuran. The starting material was re-formed when a solution of (2a) in ethanol was refluxed. The utility of borane as a protecting group for a tertiary amine function was demonstrated by the preparation of dihydroconessimine (4) from dihydroconessine (lb). The intermediate mono-borane complex (3) could be prepared by selective boronation of dihydroconessine, but was obtained in higher yield by selective deprotection of the bis-borane complex (2b), as depicted in Scheme 1. Dihydroconessine iV-oxide also was prepared from the borane complex (3) by oxidation with a peracid followed by deprotection as before. ... 

Pyridine-substituted nicotines, nornicotines, and anabasines are available from a-cyano-amines by a new synthesis. The syntheses of ( )-[l - N]nornicotine and ( )-[l - N]nicotine have been described, from cyclopropyl 3-pyridyl ketone and [ N]formamide. 4-Methylnicotine has been prepared it shows no nicotine-like pharmacological activity. " An investigation into the stereochemical factors involved in the behaviour of nicotine and related compounds in the Menschutkin reaction has been conducted.A bridged nicotine , 1,2,3,5,6,10b-hexahydropyrido[2,3-g]indolizine (44), has been synthesized by carboxylation of the dilithium derivative of 2-methylnornicotine followed by cyclisation and reduction with borane in tetrahydrofuran. Several 5-halogeno-nicotines have been prepared and their pK values and biological activities measured. ... 

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