Ligands biaryl

Chiral aluminum catalyst 2, prepared from Et2AlCl and a Vaulted biaryl ligand, is reported to be an effective Lewis acid catalyst of the Diels-AIder reaction between methacrolein and cyclopentadiene, affording the adduct in 97.7% ee [4] (Scheme 1.2). Although the Diels-AIder reaction with other a,/ -unsaturated aldehydes has not been described, that only 0.5 mol% loading is sufficient to promote the reaction is a great advantage of this catalyst. 

Recently, Wulff and coworkers demonstrated that a copper-mediated der-acemization of the vaulted biaryl ligands VANOL and VAPOL can be readily achieved in the presence of (-)-sparteine 1 (Scheme 27) [27]. 

The hydrogenation of allylic alcohols and a,/>-unsaluraled acids leads to products with a very high synthetic potential, and both transformations were used quite early for industrial applications. In both cases Ru complexes with axially chiral biaryl ligands (binap analogues) are the catalysts of choice. Here, we will dis-... 

Scheme 9 Metal-arene interactions in biaryl ligands...

XyL-TETRAPHEMP a highly EFHQENT biaryl ligand in the [DIPHOSPHINE... 

XYL-TetraPHEMP A HIGHLY EFFICIENT BIARYL LIGAND IN THE [DIPHOSPHINE RuCb DIAMINE]-CATALYZED HYDROGENATION OF SIMPLE AROMATIC KETONES... 

Brenna, E., Scaramelli, L., Serra, S. An efficient atropisomeric chiral biaryl ligand for catalytic stereoselective allylation of aldehydes a novel approach to 2,2 -binol analogs. Synlett 2000, 357-358. 

Fig. 41. Systematic variation of biaryl ligands to provide the optimum solution for diverse problems in asymmetric hydrogenation...

The catalytic activities of chiral biaryl ligands 70 and 71 have been evaluated in aziridine formation. The former is treated with borane-THF before introduction of the addends (Af-benzhydrylaldimines and ethyl diazoacetate),while the latter is used in conjunction with (MeCN)4CuBF4 to promote the transfer of the TsN group from PhI=NTs to alkenes. " The best are those with 2,6-disubstituted Ar group because they clearly define the steric and electronic profile of the active site and discourage formation of inactive L2M2 species. 

Dinuclear complexes bridged with dianionic biaryl ligands that exhibit a rare bonding mode and can be... 

In 2007, Buchwald reported that biaryl ligand 3 was effective for the sUylation of both electron-neutral and electron-rich aryl chlorides with hexameth-yldisUane (Equation 2.49). Interestingly, the use of electron-deficient aryl chlorides requires slightly modified conditions and a different biaryl hgand (Equation 2.50) [89]. 

The synthesis of isotactic copolymers from carbon monoxide and propene has been more difficult to achieve. The stereoselective copolymerization of carbon monoxide and propene has been most selective with catalysts containing alkyl-substituted bisphosphines. The catalyst containing the dialkylphosphino biaryl ligand in Figure 17.16 has been shown... 

Scheme 5.38 De-racemisation of ori/io-dihydroxylated biaryl ligands, vanol and vapol.

Very recently, Wulff s group has published a chiral catalyst for the three-component Ugi reaction based on BOROX catalysts 30 (Scheme 7.12) [29]. This BOROX catalyst was formed in situ by combination of dibenzylamine, BH SMCj, an alcohol (or phenol), and the biaryl ligand. After a large... 

Palladium-catalyzed Functionalization at N-/. Palladium-mediated cross-coupling of variedly substituted indazoles using dialkylphosphino biaryl ligands delivers excellent yields for N- arylation products. The reaction conditions are tolerant toward the presence of electron-withdrawing nitro and cyano substituents at the 6-position of benzopyrazole. Importantly, the use of aryl chlorides and bromides in these coupling reactions expands the available scope of aryl halides available for coupling at the A -1 position (eqs 6-8). 

The Ullmann reaction has been employed in the syntheses of numerous symmetrical natural compounds and biaryl ligands. With Meyers synthesis of mastigophorene A (not shown), a representative example is outlined in Equation 12.18-3, Scheme 12.18 [74]. 

Wulff and co workers reported vaulted biaryl ligand (147b) 3,3 -diphenyl-[2,2 -binaphthalene]-1,1 -diol (VANOL) and bis-phenanthrol ligand (147c) 2,2 -diphenyl-[3,3 -biphenanthrene]-4,4 -diol (VAPOL) [171]. Compared to aluminum Lewis acids... 

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