Butylborane

Monosubstituted Boranes. Only a few monoaLkylboranes are directiy available by hydroboration. Tertiary hexylborane, 2,3-dimethyl-2-butylborane [3688-24-2] (thexylborane, Thx) BH2 (5), easily prepared from 2,3-dimethyl-2-butene, is the best studied (3,60—62). It should be... 

Air-Stable boron-containing polymers can be prepared by the reaction of dicyano compounds with the / fZ-butylborane—trimethyl amine complex (449). 

The composition of the products of reactions involving intermediates formed by metaHation depends on whether the measured composition results from kinetic control or from thermodynamic control. Thus the addition of diborane to 2-butene initially yields tri-j iAbutylboraneTri-j -butylborane. If heated and allowed to react further, this product isomerizes about 93% to the tributylborane, the product initially obtained from 1-butene (15). Similar effects are observed during hydroformylation reactions however, interpretation is more compHcated because the relative rates of isomerization and of carbonylation of the reaction intermediate depend on temperature and on hydrogen and carbon monoxide pressures (16). 

On the other hand, the observed syn preference of 59a is consistent with a study of hydroboration of 59a with diborane by Schueler and Rhodes [127], who obtained a mixture of the monoalcohols (symanti = 74 26) upon oxidative work-up. A similar magnitude of. yyn-preference was found (syn anti = 73 27) in the hydroboration with a bulkier borane, 2,3-dimethyl-2-butylborane (thexyl borane) [127]. This lack of effect of the bulk of the reagent in the hydroboration of 59a is consistent with the idea that the n face of 59a is free from steric bias [127], and that the syn preference of 59a found in dihydroxylation and epoxidation is non-sterically determined [128]. 

Alkylideneamino)-butylboranes, the first known dimeric iminoboranes obtained from hydroboration reactions of nitriles 10 were prepared according to Eq. (9). 

Although dimeric (t-butylmethyleneamino)dibutylborane can be prepared by the reaction of tri-t-butylborane with pivalonitrile at temperature above 150 °C by elimination of butene. preparation at lower temperatures involving triethylamine-borane according to Eq. (11), illustrates that the formation of this iminoborane proceeds via di-n-butylborane as an intermediate 6 ... 

B-halogenated iminoboranes were also obtained by treating (t-butylmethyl-eneamino)di-n-butylborane (c.f. (Ill) with trihaloboranes at elevated temperatures 4 6 >. 

Compound (XIII) exists as a mixture of monomeric and dimeric species at room temperature. The same situation is true for the reaction products from methyl- and isopropyl-thiocyanate, respectively, with triisopropylborane, whereas the iminoborane obtained from reacting methyl-thiocyanate with tri-n-butylborane is dimeric 3 . With the exception of (XIII) these compounds have not been characterized by analysis. 

Pivaloyloxydiethylborane, 3198 Tetraethyldiborane , 3098 Tetramethyldiborane, 1779 Tetrapropyldiborane , 3580 Tri-2-butylborane, 3570 m/xo-Tributylborane, 3569 Triethylborane, 2559 Triethyldiborane, 2588 Trimethylborane, 1295 Trimethyldiborane, 1334 Tripropylborane, 3217... 

It is clear from these representative results that regioselectivity in hydroboration is controlled by steric effects. As a result, nonsymmetric internal olefins usually yield a mixture of regioisomeric alkylboranes when they react with borane. Several hindered mono- and diakylboranes with sterically demanding alkyl groups, however, have been developed for use in selective hydroboration. Disiamylborane [bis(3-methyl-2-butyl)borane, 34], thexylborane (2,3-dimethyl-2-butylborane, 35), and 9-BBN (9-borabicyclo[3.3.1]nonane) are the most frequently used reagents. Improvements of regioselectivities in hydroboration of both... 

Special methods are required for the direct reduction of RC02H to RCHO. Aldehydes can be obtained directly by the slow reduction of carboxylic acids with 2,3-dimethyl-2-butylborane in oxacyclopentane solution. 

Direct reduction of aldehydes with 2,3-dimethyl-2-butylborane proceeds rapidly and gives the corresponding alcohol. Nonetheless, reduction of carboxylic acids with the same borane (Section 18-3C) proceeds slowly and gives high yields of aldehydes. Explain why the reaction of RC02H with the 2,3-dimethyl-2-butylborane produces RCHO instead of RCH2OH. 

Addition of borane to 2,3-dimethylbut-2-ene gives 2,3-dimethyl-2-butylborane (thexylborane) which is also a synthetically useful substituted borane. 

Methylthiomethylesters.1 Treatment of DMSO with n-butyllithium followed by tri-n-butylborane affords the ate complex CH3S(0)CH2BBu3Li+(l), which converts acid chlorides into methylthiomethyl esters. 

Tribromamine hexaammoniate, see Nitrogen tribromide hexaammoniate, 0289 Tribromomethane, see Bromoform, 0367 Tribromonitromethane, 0313 f Tribromosilane, 0286 Tributylbismuth, 3565 m/xo-Tributylborane, 3563 Tri-2-butylborane, 3564 Tributylgallium, 3566 Tributylindium, 3567 Tributyl phosphate, 3568 f Tributylphosphine, 3569... 

Pivaloyloxydiethylborane, 3192 Tetraethyldiborane , 3092 Tetramethyldiborane, 1773 Tetrapropyldiborane , 3574 Tri-2-butylborane, 3564 mixo-Tributylborane, 3563... 

The triplet ketones, R2C—6, are a special case of alkoxyl radicals. Thus UV irradiation of acetone and tri-n-butylborane in the cavity of an ESR spectrometer led to the observation of two radicals, CMejOBBu", Eq. (21), and Bu". On a preparative scale the coupled products as well as BunMe2COBBu2 were isolated. 

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