C-B Bond Formations

C-C, C-O, and C-B Bond Formation by Pincer Complexes Including Asymmetric Catalysis... 

The combination of NiBr2 diglyme and 7 (R = r Pr) catalyses the crosscoupling of unactivated primary, secondary and tertiary alkyl halides with diboron reagent, pinB-Bpin, affording alkylboronates in good yields (Scheme 14.12). Compared with related nickel-catalysed carbon-carbon bond-forming reactions, this reaction exhibits an inverse reactivity order of all l halides. Thus, tertiary all l halides are more reaetive than seeondaty or primary all l halides in this C-B bond formation. ... 

The use of other transition metals Ni and Cu has been demonstrated for C—B bond formation. Percec and coworkers first reported NiCl2(dppp)-dppp for boiylation of aryl bromide with neopen-tylglycolborane [266]. Mixed ligand system NiClj(dppp)-dppf efficiently catalyzed the coupling of... 

CARBON-HETEROATOM (C-X) BOND FORMATIONS 23.3.1 C-B Bond Formations... 

Type of reaction C-B bond formation Reaction conditions Toluene, room temperature... 

Hydroboration of Activated Alkenes, Alkynes, Pyridines, and Carbonyls (C-B Bond Formation)... 

Lee K, Zhugralin AR, Hoveyda AH. Efficient C—B bond formation promoted by N-heterocychc carbenes synthesis of tertiary and quaternary B-substituted carbons through metal-free catalytic boron conjugate additions to cyclic and acyclic a,p-unsaturated carbonyls. J Am Chem Soc. 2009 131 7253-7255. 

Wu H, Radomkit S, O Brien JM, Hoveyda AH. Metal-free catalytic enantioselective C—B bond formation (pinacolato)boron conjugate additions to a,p-unsaturated ketones, esters, Weinreb amides, and aldehydes promoted by chiral N-heterocychc carbenes. J Am Chem Soc. 2012 134 8277-8285. 

In 2009, Hoveyda reported the first metal-free C-B bond formation using an NHC catalyst (Scheme 14.23). The postulated coordination of the carbene to boron in [B(pin)]2 to activate the B-B bond towards electrophiles was validated by Marder, with the isolation of such an intermediate. The initial work on enones was then expanded to the enantioselective reactions with a,p-unsaturated esters, Weinreb amides, aldehydes, and ketones, including p-substituted ones, leading to products with boron-substituted quaternary... 

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