Pyridine complex with borane

Amine-borane complexes are not very reactive toward hydroboration, but the pyridine complex of borane can be activated by reaction with iodine.160 The active reagent is thought to be the pyridine complex of iodoborane. 

The desired pyridylamine was obtained in 69 % overall yield by monomethylation of 2-(aminomethyl)pyridine following a literature procedure (Scheme 4.14). First amine 4.48 was converted into formamide 4.49, through reaction with the in situ prepared mixed anhydride of acetic acid and formic acid. Reduction of 4.49 with borane dimethyl sulfide complex produced diamine 4.50. This compound could be used successfully in the Mannich reaction with 4.39, affording crude 4.51 in 92 % yield (Scheme 4.15). Analogous to 4.44, 4.51 also coordinates to copper(II) in water, as indicated by a shift of the UV-absorption maximum from 296 nm to 308 nm. 

O-linked polymer-bound Af-substituted hydroxylamines are prepared by reduction of resin-bound oximes with borane-pyridine complex in the presence of dichloroacetic acid (Scheme 94). Other reducing systems commonly used for imine or oxime reduction are ineffective, including borane-pyridine in the presence of acetic acid. Subsequently, the A-substituted products are acylated and cleaved from the resin to afford Af-substituted hydroxamic acids 220. ... 

The cyanato- and, especially, the thiocyanato-boranes form equally stable complexes with amines, nitriles and ethyl acetate (Table 6). The Lewis acidity of these pseudohalogenoboranes and halogenoboranes, with respect to pyridine and ethyl acetate, follows the order Cl >NCS > NCO > F.79... 

A similar chiral environment is given by inclusion to cyclodextrins (CDs), cyclic oligosaccharides (3). The outside of the host molecule is hydrophilic and the inside hydrophobic. The diameters of the cavities are approximately 6 (a), 7-8 (j3), and 9-10 A (7), respectively. Reduction of some prochiral ketone-j3-CD complexes with sodium boro-hydride in water gives the alcoholic products in modest ee (Scheme 2) (4). On the other hand, uncomplexed ketones are reduced with a crystalline CD complex of borane-pyridine complex dispersed in water to form the secondary alcohols in up to 90% ee, but in moderate chemical yields. Fair to excellent enantioselection has been achieved in gaseous hydrohalogenation or halogenation of a- or /3-CD complexes of crotonic or methacrylic acid. These reactions may seem attractive but currently require the use of stoichiometric amounts of the host CD molecules. 

Reductions. iyn-Selective reduction of observed with borane-pyridine in the present predominate in the reduction with LiBHEt-.-C (Ph,P)4Pd catalyzes removal of the R SC the transformation of y,8-epoxy-o(,p-un.saiurj lers by the borane-dimethylamine complex Allyl group scavengers. In the solid-nitrogen by an (V-allyloxycarbonyl group can the presence of a borane-amine complex. 

Reductive amination with piperidines. Treatment of a piperidine and an aldehyde with the borane-pyridine complex gives the tertiary amine. 

Reductive amination Treatment of aldehydes or ketones with amines and the borane-pyridine complex in methanol in the presence of 4 A molecular sieves leads to secondary amines. 

Stirring a mixture of 2-formylamino-3-nitropyridine, benzaldehyde and borane pyridine complex in methylene chloride and acetic acid at room temperature afforded 1-benzyl-IbP. Similar derivatives of IbP were prepared from other aldehydes. The reaction of 3-benzylidenamino-2-formylaminopyridine with borane pyridine complex also led to the formation of benzyl-IbP (95JOC960). 

A general method of obtaining tertiary amine or pyridine complexes of organo-substituted boranes has been developed 172) which avoids the previous necessity of preparing intermediate alkylated diboranes in a separate step 61,66). This relatively new route involves reduction of an appropriately substituted boronate or borinate (or boroxine) with lithium aluminum hydride in the presence of the desired amine 66, 74, 129,173, 174). 

Borane (BH3) adducts of some nitrogen heterocyclic bases e.g. quinoline, aminopyridines) have been prepared. Halogenoboranes form boronium salts with such heterocycles, and some containing two different bases attached to a single boron atom, of the type (R -pyridine)(R -pyridine)aBH + 2I, have been identified. The syntheses and molecular structure determinations of complexes of phosphoranes with borane have been reported. The molecular structure of MejP.BCls has been determined by gas electron diffraction. ... 

The compounds 93 (R = Me, Et) are extremely sensitive toward oxidation and moisture and were not isolated in a pure state. Their structures were supported by NMR spectroscopy. Treatment of 93 with pyridine also gives rise to pyridine-l-boraadamantane complex 111 and starting acetylene derivative, via 1,1-deorganoboration. Accordingly, the 1-boraadamantane-TMEDA adduct (TMEDA - bis(dimethylamino)ethane) (along with Me3SnC CSnMc() is formed when the tricyclic borane 93a (R=Me) reacts with TMEDA <2003JOM(687)108>. 

Innovatory boronated carbons (manufactured in the Institute of Chemistry and Technology of Petroleum and Coal, Wroclaw University of Technology, Poland) were obtained by co-pyrolysis of coal-tar pitch with a pyridine-borane complex. In the first stage of pyrolysis (520°C) the so-called semi-coke is obtained. Further carbonization at 2500°C leads to obtaining boron-doped carbonaceous material (sample labeled 25B2). 

Boron-containing carbons synthesized by co-pyrolysis of coal-tar pitch with pyridine-borane complex (series 25Bn) have already been considered as hosts for lithium insertion [4], Unlike the commercial graphites described above, the boron-doped carbon 25B2 (WUT) as received was not suitable for direct use in the cylindrical cell due to very large and hard particles. This feature makes the coating process very difficult. 

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