Additions of Organoboron Reagents

the same authors investigated the enantioselective niekel-eata-lysed addition of aryltrifluoroborates to aromatie aldehydes in the presenee of the same ligand [(i ,i )-Et-DUPHOS]. Indeed, convenient potassium 

Cotton and G. Wilkinson, Advanced Inorganic Chemistry, 5th edn, Wiley, New York, 1988, p. 224. 

Dieguez, O. Pamies and S. Woodward, Inorg. Chim. Acta, 2008, 361,1381-1384. 

Burguete, M. Collado, J. Escorihuela, F. Galindo, E. Garcia-Verdugo, S. V. Luis and M. J. Vicent, Tetrahedron Lett, 2003,44,6891-6894. 

lizawa, M. Baba and M. Shiraishi, Chem. Pharm. Bull, 2004, 52, 818-829. 

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The first example of asymmetric rhodium-catalyzed 1,4-addition of organoboron reagents to enones was described in 1998 by Hayashi and Miyaura. Significant progress has been made in the past few years. This asymmetric addition reaction can be carried out in aqueous solvent for a broad range of substrates, such as a,/ -unsaturated ketones, esters, amides, phosphonates, nitroalkenes. The enantioselectivity is always very high (in most cases over 90% ee). This asymmetric transformation provides the best method for the enantioselective introduction of aryl and alkenyl groups to the / -position of these electron-deficient olefins. 

Senda, T. Ogasawara, M. Hayashi, T. Rhodium-Catalyzed Asymmetric 1,4-Addition of Organoboron Reagents to 5,6-Dihydro-2(lH)-pyridinones. Asymmetric Synthesis of 4-Aryl-2-piperidinones. ]. Org. Chem. 2001, 66, 6852-6856. 

Addition of Organoboron Reagents to Other Eiectron-Deficient Oiefins... 

Scheme 3.8 Asymmetric conjugate addition of organoboron reagents to a,jS-unsaturated esters [20].

Recently, Hayashi reported the details of a rhodium/diene-catalyzed 1,4-addition of organoboron reagents to quinone monoketals 108, which provides a rapid access to a-arylated tetralones in high yield and stereoselectivity [94]. 

Scheme 34.2 The addition of organoboron reagents onto fuUerenes with good efficiency and selectivity by using catalytic amounts of Rh or Pd (o-DCB, ort/to-dichlorobenzene).

Scheme 7.30 Palladium-catalyzed 1,2-addition of organoboron reagents to arylaldehydes using thioether-...

There has been only one example of a rhodium-catalyzed addition of organoboronic reagents to ketones so far. Miyaura and co-workers reported an intramolecular cy-clization of pinacol ester 77 using [RhCl(cod)]2 catalyst in the presence of potassium hydroxide, affording cyclic alcohol 78 in high yield (49) (Scheme 4.37). 

Very recently, Hoveyda et al. have demonstrated that the conjugate addition of organoboron reagents to p-substituted cyclic enones, catalysed by the readily accessible imidazolium ligand L36 and in the absence of any transition metal,... 

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