Binaphtol

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... 

In paper II the stability of the stock solutions of PS, 9a-OH-PS, 11a OH-PS and binaphtol were investigated also the short-term temperature stability,... 

Figure 16. Chromatograms resulting from injections of worked-up fermentation liquid using two types of internal standards the structurally similar AD and the structurally different binaphtol.

Another method has been described by Noyori. Optically active binaphtol reacts with LAH to afford BINAL-H (1) [3]. This reagent has proven to be an extremely efficient hydride donor achieving very high enantiomeric excesses at a low temperature. 

Deussen, H.-L. Hendrickx, E., Boutton, C., Krog. D.. Clays, K., Bechgaard, K., Persoons, A., and Bjprnhohn, T., Novel chiral iw-dipolar 6,6 -disubstituted binaphtol derivatives for second-order nonlinear optics. Synthesis and linear and nonlinear optical properties, 7. Azn. Chem. Soc., 118, 6841,1996. 

To explore the viability of chiral auxiliaries in the vinyl phosphate-p-ketophosphonate rearrangement, a series of vinyl phosphates derived from ephedrine, pseudoephedrine, (lR,2S,5R)-(-)-menthol, (15,25,35,57 )-(-i-)-isopinocampheol, (5)-(-)-2-methylbutanol, binaphtol, and (2R,4R)- or (25,45)-pentane-2,4-diol have been examined. (5)-(-)-2-methylbutanol and 2,4-pentane-2,4-diol derivatives appear as the most attractive chiral auxiliaries. 

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],... 

When (R)-binaphtol 3.7 (R = H) is used as a titanium ligand, the catalytic asymmetric oxidation of arylmethylsulfides by fe/7-BuOOH in the presence of water in CCI4 leads to (i )-sulfbxides [815, 947, 1514], In tins reaction, the initial oxidation of the sulfide into the chiral sulfoxide takes place with a moderate ee (= 50%). This step is fbllowed by further oxidation of the sulfoxides with kinetic resolution ( 1.6) [815, 1514]. To observe a high enantiomeric excess (> 90%), it is necessary to oxidize the minor (S)-enantiomer into the corresponding sulfone, and the chemical yield of the sulfoxide is in the 45 - 65% range. 

The bulkiness and stereochemistry of large steroid substituents allows stereoselective hydrolyses of unnatural enantiomers. Cholesterol together with cholesterol esterase have been used to resolve binaphtols and other diols into their enantiomers the diasteromeric dicholesteryl-diesters are hydrolyzed selectively by the crude enzyme in two steps and the final diol is a pure enantiomer. 

Despite the high level of interest in the asymmetric synthesis of a-aminophosphonic acids, not much is known about the cyclic a-aminophosphonates. The pharmaceutically interesting cyclic a-aminophosphonates are synthesized by the hydrophosphonylation of cyclic imines (thiazoUnes) in the presence of chiral lanthanoid-potassium-binaphtoxide complexes (LnPB) (Ln = lantanoid metal, P = potassium, B = binaphtol) [77],... 

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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