Reactions with Organoboron Compounds

Organoboron compounds react with carbon monoxide, which is the simplest carbonyl compound, under conditions of high temperature and pressure. Many reactions with transition metal compounds such as Fe, Ni and Co compounds are known. However, few carbonylations with main group metal compounds proceed. These reactions can be applied to, for example, the carbonylation shown in eq. (6.18) [9,34,35]. 

Reaction with Carbenoids and Isocyanides. Silylboronic ester 1 undergoes nucleophilic attack of carbenes and carbenoids, which is followed by subsequent 1,2-migration of the silyl group to give a-silylated organoboron compounds.Reaction... 

RTIX2 compounds, eg, dichlorophenyltaHium(III) [19628-33-2], can be obtained from the reaction of thaHic haHde or carboxylate with an organoboron compound (22) ... 

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. 

Cross-coupling with organoboron compounds (the Suzuki-Miyaura reaction) is by far the most popular and versatile method of cross-coupling, and has been extensively reviewed.3-5... 

Organoboron compounds cannot react without proper activation. The use of oxygen bases is inherent in the standard Suzuki-Miyaura cross-coupling method. Fluorides (usually CsF) can be used as alternative activating agents, which is particularly useful in cases when the reagents are incompatible with oxygen bases for the reactions run under anhydrous conditions,24 (66) 241 Fluoride activation can be effective, however, even under aqueous phase-transfer conditions (67) 242... 

Double asymmetric aldol reaction has been widely used for the efficient construction of the, sr -unit.10b 42 With above-described organoboron compounds (Section 3.3.1), antz -selectivity can be obtained. 

In addition, Wipf and co-workers104 have used silver(i)-catalyzed addition of zirconocenes to 3,4,6-tri-O-benzyl-D-glucal epoxide 93 for the stereoselective synthesis of a-C-glucosyl compounds 95 and 96 following a similar mechanism as in the reaction with organoaluminium and organoboron reagents (Scheme 32). 

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). 

Secondary amines have been prepared from organoboron compounds R1315, R12 BC1 or R1BCI2 (R1 = Et, Bu, /-Bu,, v-Bu, 3-hexyl, cyclopentyl etc.) by treatment with azides R2N3 (R2 = Bu, /-Bu, i-Bu, cyclohexyl, Ph etc.) and aqueous work-up. It is suggested that the reactions proceed by way of anionotropic rearrangements (equation 61)176. 

Petasis N (2005) Multicomponent reactions with organoboron compounds. In Zhu J, Bienayme H (eds) Multicomponent reactions. Wiley-VCH, Weinheim, pp 199-223... 

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