Binaphthol, asymmetric catalyst

Chiral binaphthol(BINAP)-titanates (59 X = OR) have been used as asymmetric catalysts of additions to aldehydes, and show evidence of oligomeric Ti—O—Ti... 

Asymmetric Michael reactions are known to be well-catalyzed by the AlLi-bis(binaphthoxide) complex (ALB) [51]. In order to immobilize such a highly organized multicomponent asymmetric catalyst, Sasai developed a new strategy based on the use of a catalyst analogue [52]. Si-tethered binaphthol 86 as a stable catalyst analogue was copolymerized with methyl methacrylate and ethylene glycol... 

A binaphthol titanocene catalyst has been proposed by Buchwald and Broene for use in asymmetric hydrogenation of nonfimctionalized trisubstituted olefins [829], These reactions take place undo- H2 pressure at 65°C. Acydic or cyclic olefins lead to saturated, branched alkanes with high chemical yield and enantiose-lectivity (ee 83 - 99%). Unfortunately, in most of the cases, the absolute configuration of the product has not yet been determined. 

Chiral alkyldihaloboranes are among the most powerful of chiral Lewis acids. However, since these compounds are often prone to facile decomposition to alkanes or alkenes by protonolysis or P-hydride elimination, it is difficult to recover them as alkylboronic acids. Aryldichloroboranes are more stable and can be reused as the corre onding boronic acids. We have developed chiral aryldichloroboranes 11, bearing binaphthyl skeletons with axial chirality, as asymmetric catalysts (27). (/ )-2-Dihydroxyboryl-l,r-binaphthyl (22) can be synthesized in several steps from ( )-binaphthol (27). Conversion of(/ )-22 to ( )-ll has been achieved by two different methods one via exchange of the methanol boronate with trichloroborane (MethodA), and the other via exchange of the anhydrides of boronic acids with trichloroborane (Method B) (Scheme 3). 

Chiral alkyldihaloboranes are one of the most powerful chiral Lewis acids. However, in general, since alkyldihaloboranes readily decompose into alkanes or alkenes by protonolysis or (3-hydride elimination, it is difficult to recover them as alkylboronic acids quantitatively. Aryldichloroboranes are relatively more stable and can be reused as the corresponding boronic acids. Ishihara and Yamamoto et al. have developed chiral aryldichloroboranes 21 bearing binaphthyl skeletons with axial chirality as asymmetric catalysts for the Diels-Alder reaction of dienes and a,(3-unsaturated esters (Equation 31) [29]. (J )-2-Dihydroxyboryl-l,T-binaphthyl (20) can be synthesized from (R)-binaphthol in several steps [25]. The synthesis of racemic 20a has also been reported by Kaufmann et al. [30]. Compound 20 has been converted into 21 by two dif-... 

In the catalytic enantioselective Strecker reaction, chiral aluminium complexes, especially aluminium-salen-based catalysts and aluminium-binaphthol-based catalysts have been widely used, and great achievements have been obtained. In 2010, the Li group reported a highly enantioselective Strecker reaction of achiral IV-phosphonyl imines by using primary free L-phenglycine 42 as the catalyst and diethylaluminium cyanide as the nucleophile. This work also presented the novel use of nonvolatile and inexpensive diethylaluminium cyanide in asymmetric catalysis (Scheme 19.51). ... 

Over the last few years several examples have been reported in the field of asymmetric catalysis that are based on the interaction of two centers.6,119 Recently, Shibasaki and coworkers have developed an asymmetric two-center catalyst. Scheme 3.14 shows preparation of optically active La binaphthol (BINOL). This catalyst is effective in inducing the asymmetric nitro-aldol reaction, as shown in Scheme 3.15. 

A chiral diphosphite based on binaphthol, coordinated with rhodium (I) forming a nine-member ed ring, led to an efficient hydroformylation of vinylarenes, although moderate ees were obtained (up to 46%) at mild pressure and temperature reaction conditions.364 Chiral diphosphites and phosphinite-phosphites derived from spiro[4.4]nonane-l,6-diol were synthesized. Using these catalysts in the asymmetric hydroformylation of styrene, high regioselectivity (97%) and... 

In the presence of a catalytic amount of chiral lanthanide triflate 63, the reaction of 3-acyl-l,3-oxazolidin-2-ones with cyclopentadiene produces Diels-Alder adducts in high yields and high ee. The chiral lanthanide triflate 63 can be prepared from ytterbium triflate, (R)-( I )-binaphthol, and a tertiary amine. Both enantiomers of the cycloaddition product can be prepared via this chiral lanthanide (III) complex-catalyzed reaction using the same chiral source [(R)-(+)-binaphthol] and an appropriately selected achiral ligand. This achiral ligand serves as an additive to stabilize the catalyst in the sense of preventing the catalyst from aging. Asymmetric catalytic aza Diels-Alder reactions can also be carried out successfully under these conditions (Scheme 5-21).19... 

Recently novel methods were reported to make (lR)-trans-chrysanthemic acid including optical resolutions with the (+)-3-caranediol or l,l -binaphthol monoethylether, enzymatic resolution with Arthrobacter globiformis and the asymmetric synthesis with a new Cu catalyst. These methods are reviewed in this section. 

Chiral C2-symmetric ansa-metallocenes, also referred to as bridged metallocenes, find extensive use as catalysts that effect asymmetric C—C bond-forming transformations [4]. In general, bridged ethylene(bis(tetrahydroindenyl))zirconocene dichloride ((ebthi)ZrCl2) 1 or its derived binaphtholate ((ebthi)Zrbinol) 2 [5] and related derivatives thereof have been extensively utilized in the development of a variety of catalytic asymmetric alkene alkylations. 

A fluorous version of the chiral bis-phosphine BINAP has been developed for asymmetric Heck reactions [5], Several fluorous-derivatized binaphthols and BINAP derivatives have been reported, (Scheme 10.4) [6], The silane spacer group present in one of the ligands was used to maximize the percentage fluorine on the molecule. Even so, the partition coefficient1 between FC-72 (see Chapter 3) and benzene was only 2.85, and not surprisingly, the reuse of the catalyst was poor. 

A very high asymmetric induction was observed when the reaction between cyclopentadiene and methacrolein was performed using 0.5 mol% of binaphthol catalyst 326209. Diels-Alder adduct (2R)-322 was formed with up to 97.8% ee within 4 h at — 80 °C. 

Yamamoto and colleagues prepared chiral titanium catalyst 420 from titanium tetraisopropoxide and chiral binaphthol 419 (equation 126). This catalyst gave high asymmetric inductions in various Diels-Alder reactions of a,/J-unsaturated aldehydes with cyclopen-tadiene and 1,3-cyclohexadiene260. 

The optically active catalyst 93, formed from triphenyl borate and (R)-binaphthol, catalyzes the asymmetric reaction of the dienes 94 (R1 = H or Me) with the imines 95 (R2 = Ph, 3-pyridyl or cyclohexyl). The products 96 are formed in greater than 80% ee (equation 56). Treatment of the diene 94 (R1 = H) (Danishefsky s diene) with the chiral imine 97 leads to the diastereomers 98 and 99 in the ratio 99 1 (equation 57)50. 

The Brintzinger-type C2-chiral titanocene catalysts efficiently promote asymmetric hydrogenation of imines (Figure 1.30). A variety of cyclic and acyclic imines are reduced with excellent enantioselectivity by using these catalysts. The active hydrogenation species 30B is produced by treatment of the titanocene binaphtholate derivative 30A with n-butyllithium followed by phenylsilane. 

The chiral dialuminum Lewis acid 14, which is effective as an asymmetric Diels-Alder catalyst, has been prepared from DIBAH and BINOL derivatives (Scheme 12.12). " The catalytic activity of 14 is significantly greater than that of monoaluminum reagents. The catalyst achieves high reactivity and selectivity by an intramolecular interaction of two aluminum Lewis acids. Similarly, the chiral trialuminum Lewis acid 15 is quantitatively formed from optically pure 3-(2,4,6-triisopropylphenyl)binaphthol (2 equiv) and MeaAl (3 equiv) in CH2CI2 at room temperature (Scheme 12.12). " The novel structure of 15 has been ascertained by NMR spectroscopic analysis and measurement of the methane gas evolved. Trinuclear aluminum catalyst 15 is effective for the Diels-Alder reaction of methacrolein with cyclopentadiene. Diels-Alder adducts have been obtained in 99% yield with 92% exo selectivity. Under optimum reaction conditions, the... 

Terada and co-workers reported a novel guanidine catalyst with a chiral binaphthol backbone for the asymmetric addition of dicarbonyl compounds to nitro-olefins [126]. Substitution on the binaphthol backbone dramatically increased enantioselectivity. 

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