BINOL polymeric

This investigation was complemented by a series of experiments where the car-binol precursors of the four monomers were used as monomers in the presence of trifluoroaeetic acid or its anhydride. The results were similar to those obtained in an earlier study with aromatic carbinols109 and indicated that one of the active species present in the polymerizations of the 2-alkenylfurans must be the ester derived by the initial reaction of the vinyl bond with the acid ... 

Polymerization. Complexes of BINOL-derived crown ethers with KO-t-Bu or BuLi have been used as initiators in the asymmetric polymerization of methacrylates. Thus optically active polymers are obtained with 80-90% isotacticity. Complexes of BINOL with Diethylzinc or CdMe2 also initiate the asymmetric... 

The results from four other reactions with catalyst 407 are summarized in Sch. 56. Induction ranged from 5 to 49 % ee, below the value obtained (74 % ee) from the reaction of enone 404 and malonate 405. The reaction of malonate 405 with the unsaturated carbonyl compounds 413, 392 and 414 all failed to produce product. The reaction of 405 with acrolein led to polymerization. The stoichiometry of catalyst formation is crucial for optimization of the Michael adduct. The reaction between enone 404 and nitroester 411 with catalyst 394 generated with 2.0 equiv. BINOL gave the double Michael adduct 416 as the major product. When the amount of BINOL is increased to 2.45 equiv. the Michael adduct 415 constitutes a minimum of 80 % of the product mixture. Larger amounts of BINOL resulted in an insoluble catalyst. 

The BINOL-Ti complex-catalyzed addition of allylsilane to aliphatic and aromatic aldehydes has been reported by Carreira [43], The catalyst is prepared from BINOL and polymeric Tip4 (Sch. 9). The presence of a small amount of CH3CN is crucial to achieving not only high catalytic activity but also high enantioselectivity. 

Chiral an a-metallocene complexes have become useful catalysts in asymmetric polymerization reactions [73]. While enantio-resolution of a <3-metaIlocene race-mates cannot yield more than 50% of a particular enantiomer, the readily accessible racemate of a biphenyl-bridged metallocene complex (we abbreviate to bi-phecp -M M = Ti, Zr) has been quite recently reported to give enantio-pure ansa-titanocene and -zirconocene complexes through binol-induced asymmetric trans-... 

Nonracemic Ti-BINOLate (BINOL = l,l -bi-2-naplilli()l) and Ti-TADDOLate (TADDOL = a,a,a, a -tetraaryl-2,2-dimethyl-l,3-dioxolan-4,5-dimethanol) complexes are also effechve chiral catalysts for the asymmetric alkylation of aldehydes [9-11]. Seebach developed polystyrene beads with dendritically embedded BINOL [9] or TADDOL derivatives 11 [10, 11]. As the chiral ligand is located in the core of the dendritic polymer, less steric congeshon around the catalyhc center was achieved after the treatment with Ti(OiPr)4. This polymer-supported TiTADDOLate 14 was then used for the ZnEt2 addition to benzaldehyde. Chiral 1-phenylpropanol was obtained in quantitahve yield with 96% ee (Scheme 3.3), while the polymeric catalyst could be recycled many times. 

A bimetallic titanium complex of BINOL derivative can be used to catalyze the asymmetric carbonyl-ene reaction [46]. Insoluble polymeric catalyst 74 was prepared from a self-assembly of Ti(OiPr)4 and non-crosshnked copolymers with (R)-binaphthol pendant groups (Scheme 3.22) [47]. The self-assembled polymeric Ti complex is insoluble in organic solvent and catalyzed the carbonyl-ene reaction of glyoxylate 75 and a-methylstyrene 76. When the reaction of 75 and 76 was carried out with 20mol% of 74 in Gl pCf at room temperature, an 85% yield of the product with 88% ee was obtained. Following its recovery by filtration, this catalyst was reused five times with full retenhon of its activity and enantioselectivity, without further treatment... 

Poly-L-leucine and a polymeric BINOL the epoxidation of enones. Poly-L-leucine imni An air- and moisture-stable ionic liquid in. hiral (salen)Mn(III) complexes that are used i Ketone reductions. Corey s oxazaboroh virane reduction. A cheap borane source for tl. ilso modifications, for example, using alunui jerivative 85." ... 

Two interesting bifunctional polymeric ligands have been reported. Incorporating BINAP and BINOL functionalities, and 130 have been used in ruthenium-catalyzed transformations with considerable success. 

Polymeric BINOL aluminum chloride. Prepared by Ni(0)-catalyzed cross- coupling of chiral 6,6 -dibromo-BINOL diacetate, hydrolysis, and treatment with EtjAlCl, the chiral catalyst is effective for the Mukaiyama aldol reaction. 

Scheme 19 Coordination of polymerizable phosphorous ligands and (i )-Bu2BINOL to platinum (45) and polymerization with EGDMA creates polymers (P-30 through P-33b) with binding sites selective towards (i )-BINOL derivatives following removal of the template.

It is relatively rare for the interactions with the polymeric support to be beneflcial to catalytic performance. However, one example of this was observed upon the deliberate positioning of a binol ligand in close proximity to polystyrene via amide linkages [15], which resulted in enhanced performance in the titanium-catalyzed addition of diethylzinc to aldehydes (Figure 5.2b). 

Previously unknown (biaryl)hydroxyl acid catalysts, disulfonimides 196 were prepared in five steps from BINOL (14AGE8765). These Lewis acid precursors allowed for the catalysis of Mukaiyama aldol reactions at unprecedented rates. A microwave-assisted protocol was described for the preparation of cyclic sulfamides 197 these reactions do not use catalysts and show increased yields, shorter reaction times, and less polymeric by-product than traditional heating (14PS285). 

Soto and coworkers have developed chiral polyphosphazene block copolymers (13CEJ5644). Their synthesis starts with consecutive reactions of (trimethylsilyl)phosphorimidoyl trichloride 160 and methylphenyl-phosphorimidoyl chloride 161 monomers (Scheme 42). The polymerization was initiated by phosphazene 159 and gave the polyphosphazenes 162a—c with different ratio of block motifs. The substitution of chlorine atoms by binol was accomplished in the presence of cesium carbonate as a base and the resulting polymers 162a—c isolated in 66—77% yields. 

As expected, the cis/trans diastereoselectivity is influenced by the structure of the catalyst precursor, and is controllable by choosing a proper catalyst and polymerization conditions. The enantioselectivity (the relative stereochemistry between the rings) of PMCP is also affected by the catalyst structure. Complexes la, lb (Figure 19.2), and 2a, which give atactic poly(a-olefin)s, produce atactic PMCP, and the isoselective catalysts 3 and 4a yield isotactic PMCPs. These differences in enantioselectivity versus catalyst type are consistent with those for the polymerization of a-olefins. trans-Isotactic polymers can be optically active (chiral) if homochiral catalysts are used. The Waymouth research group showed that the MAO-activated homochiral ansa-zirconocene BINOL complex 5 (BINOL = l,l -bi-2-naphtholate Figure 19.2) gave optically active trany-polymer. 

The effect of the template on MIP-CD efQdency during the catalytic process has been studied. Diverse bis-naphthols were tested as the template (Fig. 2.11), and the polymerization was carried out using EPI, diepoxyethane, or diglycidyl ether of glycerol [39]. The best MIP-CD was reahzed using l,l-bisnaphtol as template and EPI as cross-linker 0-CD(EPI)(Binol)ii ). 

To facilitate catalyst recovery, polymeric and dendrimeric TADDOL, and BINOL ligands have been used for the titanium-catalyzed diethylzinc addition reaction [49]. Moreover, ionic liquids and fluorous solvents have also been used as the reaction media to facilitate the separation of ligands [50]. The microporous metal-organic frameworks prepared from BINOL derivatives were applicable to heterogeneous diethylzinc addition to aldehydes in the presence of excess amount of Ti(O Pr)4 [51]. 

The catalytic enantioselective addition of allylsilane to aliphatic or aromatic aldehydes seems to be more challenging. BINOL-TiF2 prepared from the reaction of BINOL and polymeric TiF4 was reported to promote the additions of allylsilane to aldehydes with the enantioselectivities of 64-91% [89]. Although the exact structure... 

Asymmetric cyanosilylation of aliphatic aldehydes were also performed with the polymeric Ti(OTr)2-BINOLate (147) (Scheme 19.28). The enantioselectivity... 

Fig. 9.34 Construction of asymmetric reaction field for acetylene polymerization by dissolving Ziegler-Natta catalyst, Ti(0-n-Bu)4—AlEts, into the chiral nematic LC. The N -LC contains an axially chiral binaphthyl derivative, (R)- or (5)- 2,2 -PCH506-Binol as a chiral dopant...

In 2001, we extended this chemistry to the use of multinucleus BINOL-aluminum catalysts, which could be regarded as LLA catalysts, for a number of Diels-Alder reactions (Fig. 10) [51]. These complex structures have been elucidated on the basis of NMR studies, as well as gas generation measurements. Such kind of aluminoxide catalysts can be viewed as chiral versions of methyl aluminoxane (MAO), a very powerful Lewis acid co-catalyst for cationic polymerization of olefins. We thus believed further extension of this chemistry should be very promising. 

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