BINOL catalysis catalyst

Enantioselective catalysis of S alkylation has been achieved.91 A BINOL-phosphoramidite catalyst (o-methoxyphenyl analog) similar to that in Entry 3 in Scheme 8.7 gave good results. 

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. 

An NMR kinetic study of a phosphine-catalysed aza-Baylis-Hillman reaction of but-3-enone with arylidene-tosylamides showed rate-limiting proton transfer in the absence of added protic species, but no autocatalysis.175 Brpnsted acids accelerate the elimination step. Study of the effects of BINOL-phosphinoyl catalysts sheds light not only on the potential for enantioselection with such bifunctional catalysis, but also on their scope for catalysing racemization. 

We reported the first examples of asymmetric catalysis of intramolecular carbonyl-ene reactions of types (3,4) and (2,4) using the BINOL-derived titanium complex (1) [80,83]. The catalytic 7-(2,4) carbonyl-ene cyclization gives the oxepane with high ee, and gem-dimethyl groups are not required (Sch. 27). In a similar catalytic 6-(3,4) ene cyclization, the fram-tetrahydropyran is preferentially produced, with high ee (Sch. 28). The sense of asymmetric induction is exactly the same as observed for the glyoxylate-ene reaction—the (f )-BINOL-Ti catalyst provides the (R)-cyclic alcohol. 

Yamamoto et al. have reported an asymmetric catalysis of carbonyl-ene reaction, which employs chloral as the enophile using an optically pure 3,3 -bissi-lylated binaphthol (BINOL) aluminum catalyst (Scheme 2) [12]. The 3,3 -diphe-nyl BINOL-derived aluminum catalyst provides the racemic product in low yield. 

In 1992, Shibasaki et al. reported for the time an application of chiral heterobimetallic lanthanoid complexes (LnLB) as chiral catalysts in asymmetric catalysis, namely the catalytic asymmetric nitroaldol reaction (Henry reaction), which is one of the most classical C-C bond forming processes [11]. Additionally, this work represents the first enantioselective synthesis of (3-nitroalcohol compounds by the way of enantioselective addition of nitroalkanes to aldehydes in the presence of a chiral catalyst. The chiral BINOL based catalyst was prepared starting from anhydrous LaCl3 and an equimolar amount of the dialkali metal salt of BINOL in the presence of a small amount of water [9]. 

For the catalytic asymmetric FC reaction, the application of chiral titanium complexes of BINOL derivatives was first realized by Mikami and coworkers in the reaction of electron-rich aryl and vinyl ethers with fluoral [245]. For the FC reaction of anisole, it was found that the catalytic activity and enantioselectivity of BINOL-Ti catalysts were critically influenced by the substituents of BINOL derivatives. The electron-withdrawing bromo atoms at 6,6 -positions of BINOL turned out to be beneficial to the catalysis, the trifluoroethanol derivatives were obtained in high yield (89%) and up to 90% ee with a p o isomer ratio of 4 1. The FC reaction of vinyl ether with fluoral catalyzed by BINOL-TiCb (10 mol%) gave a mixture of allylic alcohols in which the major isomer was usually the Z-alkene. The increase of bulkiness of silyl group is favorable for the formation of FC products with very high enantiomeric excess (Scheme 14.105). 

Ding and coworkers [58] have also reported the use of chiral self-supported BINOL-Zn catalysts for the heterogeneous asymmetric catalysis of epoxidation of... 

The 2-pyrones can behave as dienes or dienophiles depending on the nature of their reaction partners. 3-Carbomethoxy-2-pyrone (84) underwent inverse Diels-Alder reaction with several vinylethers under lanthanide shift reagent-catalysis [84] (Equation 3.28). The use of strong traditional Lewis acids was precluded because of the sensitivity of the cycloadducts toward decarboxylation. It is noteworthy that whereas Yb(OTf)j does not catalyze the cycloaddition of 84 with enolethers, the addition of (R)-BINOL generates a new active ytterbium catalyst which promotes the reactions with a moderate to good level of enantio selection [85]. 

The structure of the active catalyst and the mechanism of catalysis have not been completely defined. Several solid state complexes of BINOL and Ti(0-/-Pr)4 have been characterized by X-ray crystallography.158 Figure 2.4 shows the structures of complexes having the composition (BIN0Late)Ti2(0-/-Pr)6 and (BINOLate)Ti3(O-/-Pr)10. 

The self-assembly of a chiral Ti catalyst can be achieved by using the achiral precursor Ti(OPr )4 and two different chiral diol components, (R)-BINOL and (R,R)-TADDOL, in a molar ratio of 1 1 1. The components of less basic (R)-BINOL and the relatively more basic (R,R)-TADDOL assemble with Ti(OPr )4 in a molar ratio of 1 1 1, yielding chiral titanium catalyst 118 in the reaction system. In the asymmetric catalysis of the carbonyl-ene reaction, 118 is not only the most enantioselective catalyst but also the most stable and the exclusively formed species in the reaction system. 

This chapter focuses on several recent topics of novel catalyst design with metal complexes on oxide surfaces for selective catalysis, such as stQbene epoxidation, asymmetric BINOL synthesis, shape-selective aUcene hydrogenation and selective benzene-to-phenol synthesis, which have been achieved by novel strategies for the creation of active structures at oxide surfaces such as surface isolation and creation of unsaturated Ru complexes, chiral self-dimerization of supported V complexes, molecular imprinting of supported Rh complexes, and in situ synthesis of Re clusters in zeolite pores (Figure 10.1). 

The role of multicomponent ligand assembly into a highly enantioselective catalyst is shown in the enantioselective catalysis for the carbonyl-ene reaction (Table 8.9). The catalyst is prepared from an achiral precatalyst, Ti(0 Pr)4 and a combination of BINOL with various chiral diols such as TADDOL and 5-Cl-BIPOL in a molar ratio of 1 1 1 (10mol% with respect to the olefin and glyoxylate) in... 

List and coworkers reasoned that BINOL phosphates (specific Brpnsted acid catalysis) could be suitable catalysts for an asymmetric direct Pictet-Spengler reaction [26], Preliminary experiments revealed that unsubstituted tryptamines do not undergo the desired cyclization. Introduction of two geminal ester groups rendered the substrates more reactive which might be explained by electronic reasons and a Thorpe-Ingold effect. Tryptamines 39 reacted with aldehydes 40 in the presence of phosphoric acid (5)-3o (20 moI%, R = bearing 2,4,6-triisopropyI-... 

Two years later, Terada and coworkers described an asymmetric organocatalytic aza-ene-type reaction (Scheme 28) [50], BINOL phosphate (7 )-3m (0.1 mol%, R = 9-anthryl) bearing 9-anthryl substituents mediated the reaction of A-benzoylated aldimines 32 with enecarbamate 76 derived from acetophenone. Subsequent hydrolysis led to the formation of P-amino ketones 77 in good yields (53-97%) and excellent enantioselectivities (92-98% ee). A substrate/catalyst ratio of 1,000 1 has rarely been achieved in asymmetric Brpnsted acid catalysis before. 

Until 2006, a severe limitation in the field of chiral Brpnsted acid catalysis was the restriction to reactive substrates. The acidity of BINOL-derived chiral phosphoric acids is appropriate to activate various imine compounds through protonation and a broad range of efficient and highly enantioselective, phosphoric acid-catalyzed transformations involving imines have been developed. However, the activation of simple carbonyl compounds by means of Brpnsted acid catalysis proved to be rather challenging since the acid ity of the known BINOL-derived phosphoric acids is mostly insufficient. Carbonyl compounds and other less reactive substrates often require a stronger Brpnsted acid catalyst. 

The last few years have witnessed major advances in the use of small organic molecules as organic acid catalysts in asymmetric catalysis [1], Selected examples of such organic acid catalysts include urea and thiourea [2], TADDOL [3], BINOL [4], and phosphoric acid derived from BINOL [5] (Figure 2.1). 

The Rawal group next applied diol catalysis to the enantioselective vinylogous Mukaiyama aldol (VMA) reaction of electron-deficient aldehydes [105]. Screening of various known chiral diol derivatives, including VANOL, VAPOL, BINOL, BAMOL, and TADDOL, revealed that 38a was the only catalyst capable of providing products in acceptable levels ofenantioselection (Scheme 5.55). Subsequent to this work, Scettri reported a similar study of TADDOL-promoted VMA reactions with Chan s diene [106]. 

Shibasaki and colleagues achieved further efficient catalysis using a zinc complex as a catalyst [5,14], which was prepared from Et2Zn and linked-BINOL... 

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