Acetylene organoboron compounds

Intermolecular dimerization has also been effected by a comparable protocol.24-26 Treatment of triethylborane with silver nitrate and sodium hydroxide in water at 25°C led to the rapid evolution of M-butane (72%), ethylene (9%), and ethane (9%). Reaction of two different alkylboranes led to statistical mixtures of dimerized and cross-coupled products. Furthermore, this strategy has been used successfully in the synthesis of olefins from dihydroborated internal acetylenes,27 and in polymerizations of bifunctional organoboron compounds.28... 

Later it was shown that a wide range of organoboron compounds, including boronic acids, boronates, and acetylene hydroboration products, readily react with such hyperva-lent iodine componnds as iodonium salts and Koser s or Zefirov s iodinanes in aqueous solvents in the absence of base, giving near quantitative yields of the coupling products (Scheme Phosphine-free and phosphine-assisted catalysis were equally effective. 

Bombykol is an estrogenic hormone ((I0E,12Z)-hexadecadiene-l-ol) which induces sexual excitement in a male silkworm. Bombykol is prepared by the hydroboration of acetylene compounds with a catecol boron compound and a cross coupling reaction with palladium catalyst, etc., as shown in Scheme 6.4 [41—47], The organoboron compounds are used for leucotriene intermediates [48], L-ribose and amino acids [47], etc., as the others. 

Although clearly of use in the synthesis of certain alkylboron compounds, particularly tri-n-alkylboranes and alkylboron hydrides, the hydroboration reaction (developed mainly by H. C. Brown) is of considerable significance in synthetic organic chemistry, as the resulting organoboron compound can be used (without being isolated) as an intermediate in the conversion of olefins or acetylenes into other hydrocarbons (parafi or olefins), alcohols, aldehydes, ketones, carboxylic acids or amines. 

In recent years, catalytic carboalumination of acetylenes has found use in the synthesis of cycloalkenes [98-101], trisubstituted olefins, homoallyl alcohols, a,p-unsaturated esters, 1,3-enyne-l,4-disilanes [102-105], a,p-unsaturated organoboron or zirconium compounds, and also natural and biologically active compounds. For example, key synthons for the preparation of prostaglandins [86,... 

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