Boron organoboron compounds

Palladium-catalyzed carbon-carbon bond forming reactions like the Suzuki reac-tion as well as the Heck reaction and the Stille reaction, have in recent years gained increased importance in synthetic organic chemistry. In case of the Suzuki reaction, an organoboron compound—usually a boronic acid—is reacted with an aryl (or alkenyl, or alkynyl) halide in the presence of a palladium catalyst. 

The sources of the required organoboron compounds are manifold. The most popular organoboron compounds for this method, boronic acids and their esters (boronates), can be obtained through ... 

The application of in situ-generated (alkoxy)palladium(II) species (Scheme 14.23) can be extended to reactions of a-carbonates with organoboron compounds. Crosscouplings of allenes 108 with aryl (or alkenyl) boron acids or their esters catalyzed by a palladium(O) complex afforded the 2-aryl(alkenyl)-l,3-butadienes 109 in excellent yields (Scheme 14.24) [53], The coupling reactions of 9-BBN-derived intermediates such as ester 111 can be accelerated by applying K3P04 as additive (Eq. 14.15). 

The overall mechanism is closely related to that of the other cross-coupling methods. The aryl halide or triflate reacts with the Pd(0) catalyst by oxidative addition. The organoboron compound serves as the source of the second organic group by transmetala-tion. The disubstituted Pd(II) intermediate then undergoes reductive elimination. It appears that either the oxidative addition or the transmetalation can be rate-determining, depending on reaction conditions.134 With boronic acids as reactants, base catalysis is normally required and is believed to involve the formation of the more reactive boronate anion.135... 

Atmospheric boron is in the form of particulates or aerosols of borides, boron oxide, borates, boranes, organoboron compounds, trihalide boron compounds, or borazines. The half-time persistence of airborne boron particles is short, usually on the order of days (USPHS 1991). 

Borazarophenanthrene was the first representative of a new class of heteroaromatic compounds containing boron atoms in six-membered aromatic rings.4 These compounds are of a different order of stability from previously known types of organoboron compounds, being chemically similar to normal aromatics, and their discovery has opened up a new field of aromatic chemistry. The procedure indicated here has been used to prepare a large number of related aromatic systems. 

Steinberg, H., Brotherton, R. J. Organoboron Chemistry, Vol. 2. Boron-Nitrogen and Boron-Phosphorus Compounds. New York Interscience 1966. 

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