Carbon-boron bond formation

Carbon-based 7]7-ligands, in molybdenum carbonyls, 5, 483 Carbon-boron bond formation... 

The Pd-catalyzed cross-coupling reaction of the pinacol ester of diboronic acid with aryl halides and triflates gives a direct procedure for various functionalized arylboronic esters (Table 6), which are useful for highly efficient and selective carbon-carbon bond formation by Pd catalysts (Sect. III.2.2). The combination of PdCl2(dppf) with KOAc (and dppf) is effective in the carbon-boron bond formation. KOAc is essential not only to accelerate the reaction but also to prevent the formation of biaryl by-products. 

The PdCl2(CH3CN)2-catalyzed phosphination and borylation of aryl halides have also emerged as powerful methods for carbon-phosphorus and carbon-boron bond formation, respectively. 

Partyka, D.V., Zeller, M., Hunter, A.D. and Gray, TG. (2006) Relativistic functional groups Aryl carbon-gold bond formation by selective transmetalation of boronic acids. Angewandte Chemie International Edition, 45, 8188-8191. 

Recently, interest in copper-catalyzed carbon-heteroatom bond-forming reactions has shifted to the use of boronic acids as reactive coupling partners [133], One example of carbon-sulfur bond formation is displayed in Scheme 6.65. Lengar and Kappe have reported that, in contrast to the palladium(0)/copper(l)-mediated process described in Scheme 6.55, which leads to carbon-carbon bond formation, reaction of the same starting materials in the presence of 1 equivalent of copper(II) acetate and 2 equivalents of phenanthroline ligand furnishes the corresponding carbon-sulfur cross-coupled product [113]. Whereas the reaction at room temperature needed 4 days to reach completion, microwave irradiation at 85 °C for 45 min in 1,2-dichloroethane provided a 72% isolated yield of the product. 

C-M bond addition, for C-C bond formation, 10, 403-491 iridium additions, 10, 456 nickel additions, 10, 463 niobium additions, 10, 427 osmium additions, 10, 445 palladium additions, 10, 468 rhodium additions, 10, 455 ruthenium additions, 10, 444 Sc and Y additions, 10, 405 tantalum additions, 10, 429 titanium additions, 10, 421 vanadium additions, 10, 426 zirconium additions, 10, 424 Carbon-oxygen bond formation via alkyne hydration, 10, 678 for aryl and alkenyl ethers, 10, 650 via cobalt-mediated propargylic etherification, 10, 665 Cu-mediated, with borons, 9, 219 cycloetherification, 10, 673 etherification, 10, 669, 10, 685 via hydro- and alkylative alkoxylation, 10, 683 via inter- andd intramolecular hydroalkoxylation, 10, 672 via metal vinylidenes, 10, 676 via SnI and S Z processes, 10, 684 via transition metal rc-arene complexes, 10, 685 via transition metal-mediated etherification, overview,... 

Schuster and co-workers discovered that 1,4-dicyanonaphthalene solutions containing an alkyltriphenylborate salt, when irradiated, yield one-eleetron oxidation of the alkyltriphenylborate leading to carbon-boron bond cleavage and formation of free alkyl radicals [23]. In Gottschalk s hands [24, 25], it was shown that ionic salt pairs formed from cyanine dyes and alkyltriphenylborates (Figure 1) could be used as photoinitiators [26] that were active in the visible region of the spectrum. 

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