Borane trialkyl, preparation, 70 reactions

BCl, BBr, and BI undergo exchange reactions to yield mixed boron hahdes. Exchange reactions also occur with trialkyl, triaryl, trialkoxy, or triaryloxy boranes and with diborane. Anhydrous metal bromides and iodides can be prepared by the exchange reaction of the metal chloride or oxide and BBr or BI (21)-... 

The carbanions take up 02 and these take up protons to give hydroperoxides in good yields. But because they are explosive in nature, they are not usually isolated and on reduction with sodium sulphite on trialkyl phosphite give alcohols. Alcohols can also be prepared via hydroperoxy molybdenum complexes and alkyl boranes. These reactions are summarized as follows ... 

The alkylation of activated halogen compounds is one of several reactions of trialkyl-boranes developed by H. C. Brown1560 (see also 5-12, 5-19, 8-24 to 8-28, etc ). These compounds are extremely versatile and can be used for the preparation of many types of compounds. In this reaction, for example, an alkene (through the BR3 prepared from it) can be coupled to a ketone, a nitrile, a carboxylic ester, or a sulfonyl derivative. Note that this is still another indirect way to alkylate a ketone (see 0-95) or a carboxylic acid (see 0-96), and provides an additional alternative to the malonic ester and acetoacetic ester syntheses (0-94). 

N-Trialkyl-B-trihaloborazines can be prepared without difficulty from alkylammonium halide or alkylamine and trihaloborane 4> when the resulting alkylammonium tetrahaloborate or alkylamine-trihalo-borane is refluxed in chlorobenzene. Yields are nearly quantitative in most cases. This same observation holds true for N-triaryl-B-trihalo-borazines. Extensive studies using thermogravimetric methods in addition to preparative methods did not provide for the isolation or identification of any intermediates between the amine-trihaloborane and the borazine stage of the reaction 45 4fl>. 

The reaction undergone by alcohols with trialkyl- and triaryl-boranes in the presence of pivalic acid, to give borinic esters, and the thermal cyclization of bis(dialkylborinates) to boronates, are discussed briefly in Section II. Many borinates have been prepared in quantitative yield from mono-, di-, oligo-, and poly-saccharides,338,108 and mixed... 

Oxidation of trialkyl borates and of trialkoxyboroxines. Trialkyl borates, B(0R)3, prepared by reaction of primary and secondary alcohols with borane-dimethyl sulfide, are oxidized by PCC to aldehydes and ketones in good yield. This indirect oxidation of alcohols does not involve formation of water, which could be detrimental in some cases. Of even greater interest, carboxylic acids can be converted into aldehydes by reaction with borane-dimethyl sulfide to form a tri-alkoxyboroxine followed by oxidation with PCC (equation I). 

Other uses of diborane include the preparation of boron nitride by the reaction of diborane with ammonia, as a catalyst for polymerization, and for the conversion of olefins to trialkyl bo-ranes. It is also used in the conversion of amines to amine boranes and as a selective reducing agent with carbonyl compounds such as aldehydes and ketones to form alcohols. 

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