Binaphtol catalyst

H. Sasai, S. Watanabe, M. Shibasaki, A New Practical Preparation Method for Lanthanum-Lithium-Binaphtol Catalysts (LLBs) for Use in Asymmetric Nitroaldol Reactions, Enantiomer, 1997,2,267-271. 

The second approach starts from achiral allylic substrates and uses a chiral metal catalyst. Among all ligands which have been tested binaphtol-derived phosphoramidites like 174 have led to excellent regio- and enantioselectivities (equation 103) °. Highly stereoselective substitutions are also obtained using ligand 175 (Taniaphos, equation 104... 

Lewis add complexes formed by the reactions of various aminoalcohols with Et2AlG [778, 824] or by the reaction of Et2Zn with a chiral sulfamide [806] have displayed a low efficiency in the asymmetric condensations of ketene and thioketene silyiacetals derived from acetic acid with aldehydes. Disappointing se-lectivities have also been observed with some binaphtol-titanium complexes [778]. However, Mikami and Matsukawa [1296] recently performed the enantioselective condensation of various aldehydes with acetic acid derivatives in the presence of a chiral binaphtol-titanium complex. Good selectivities were observed when the reaction was performed at 0°C in toluene (Figure 6.95). Quaternary ammonium fluorides derived from cinchona alkaloids have been proposed as catalysts to perform additions of enoxysilanes derived from ketones to PhCHO, but the observed selectivities are modest [1303],... 

Another approach starts from achiral allylic substrates and uses a chiral metal catalyst. Binaphtol-derived phosphoramidites like 132 have led to best regioselectivities and enantioselectivities among a vast number of tested ligands (Scheme 2-48, eq. (a)). Highly stereoselective substitutions have been described using the ligand 133... 

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