Reactions catalyzed by cyclodextrin

See for example the pioneering work of Breslow Bres-low, R. Dong, S. D. Biomimetic Reactions Catalyzed by Cyclodextrins and their Derivatives Chem. Rev. 1998, 98,1997-2011 and Breslow, R. Biomimetic Chemistiy and Artificial Enzymes - Catalysis by Design Acc Chem. Res. 1995,28,146-153. 

Sunamoto et al. 94) have studied the reaction of (14) with 2,4-dinitro-phenyl sulfate in aqueous organic solvent with 0.1 A sodiiun hydroxide. The rate of esterolysis by (14) was greater than the rate of the reaction catalyzed by -cyclodextrin. Better binding by the paracyclophane cavity and the greater nucleophilicity of the oxime group as compared to the secondary hydroxyl group of jS-cycdextrin were cited to explain the difference in catalytic efficiency. 

In Table XXII are shown reactions catalyzed by cyclodextrins. It is shown that some condensation reactions are also remarkably catalyzed by the use... 

Breslow, R., Dong, S. D., (1998) Biomimetic reactions catalyzed by cyclodextrins and their derivatives Chem. Rev. 98, 1997-2011. 

R. Breslow, S.D. Dong, Biomimetic Reactions Catalyzed by Cyclodextrins and Their Derivatives , Chem. Rev., 98, 1997 (1998)... 

Biomimetic reactions catalyzed by cyclodextrins and their derivatives 98CRV1997. 

A acceptor, substrates to CGT have aG units attached 1-4 Figure 2. Reactions catalyzed by cyclodextrin a 1-4 glucosyltransferase. 

We examined exchange of deuterium into the methyl group of ketone 12 catalyzed by the three isomers of cyclodextrin bisimidazole and also by p-cyclodextrin monoimidazole (5) in D2O solution with 14% CD3OD, buffered at pH 6.2 with phosphate buffer, at 35 °C [12]. We saw essentially no deuterium incorporation into the methyl group over 10 hours with the buffer alone, or the buffer with added simple cyclodextrin. However, all four of the cyclodextrin derivatives (5,6,7, and 8) catalyzed significant deuterium incorporation into the methyl group over the same period. The AB (6) and AC (7) isomers were only marginally more effective than was the monoimidazole catalyst, but the AD isomer 8 was clearly better. A pH vs rate plot for the reaction catalyzed by the AD isomer showed a bell-shaped curve with a rate maximum near pH 6.2, as expected for bifunctional catalysis, while the reaction catalyzed by cyclodextrin-6-imidazole 5 showed a simple increase to a plateau at pH above 7.5, as expected for monofunctional base catalysis. 

Breslow, R., and Dong, S. D. "Biomimetic Reactions Catalyzed by Cyclodextrins and Their Derivatives." Chem. Ren, 98,1997-2011 (1998). Zhang, B., and Breslow, R. "Ester Hydrolysis by a Catalytic Cyclodextrin Dimer Enzyme Mimic with a Metallobipyridyl Linking Group." /. Am. Chem. Soc., 119,1676-1681 (1997). 

Hydrogen Transfer Reactions Catalyzed by Ruthenium Complexes Linked to P-Cyclodextrin 43... 

Complexes of Rh, Pt, and Pd with the same ligands were active in the biphasic hydrogenation of chloro- and bromonitrobenzenes. At 80-100 °C and 20 bar H2 pressure the main products were the corresponding chloro-and bromoanilines, up to 99.8 % yield (Scheme 10.5) [12]. The selectivity of similar reactions catalyzed by a Rh/TPPTS was only about 90 %, i.e. the attached cyclodextrin moiety further decreased the extent of hydrodehalogenation, probably by complexation of the halonitroaromatic substrate. 

Preparation and catalysis of disubstituted cyclodextrin as an excellent enzyme model is demonstrated by the RNAase model reported by Breslow et al. (68, 83). The enzyme models 10 and II, derived from 1, show a bellshaped pH versus rate profile for the hydrolysis of the cyclic phosphate of 4-terf-butylcatechol, indicating the cooperative catalysis by two imidazole groups (Fig. 21). The reactions catalyzed by 10 and II give exclusively 12 and 13, respectively. This interesting specificity indicates that the geometry of the P—O bond cleavage is quite different from each other. Another interesting enzyme-like kinetic behavior that these hosts exhibited is successful demonstration of the so-called bell-shaped pH profile. 

FlG. 30. Reaction scheme of allylation and oxidation of hydroqui none derivatives catalyzed by cyclodextrin. 

The situation is complex. In another study we examined the cyclization of compound 54 catalyzed by cyclodextrin bis-imidazoles [140]. This dialdehyde can perform the intramolecular aldol reaction using the enol of either aldehyde to add to the other aldehyde, forming either 55 or 56. In solution with simple buffer catalysis both compounds are formed almost randomly, but with the A,B isomer 46 of the bis-imidazole cyclodextrin there was a 97 % preference for product 56. This is consistent with the previous findings that the catalyst promotes enolization near the bound phenyl ring, but in this case the cyclization is most selective with the A,B isomer 46, not the A,D that we saw previously. Again the enolization is reversible, and the selectivity reflects the addition of an enol to an aldehyde group. The predominant product is a mixture of two stereoisomers, 56A and 56B. Both were formed, and were racemic despite the chirality of the cyclodextrin ring. 

Hydrohalogenation of crotonic acid in a crystalline a-cyclodextrin complex gives ( + )-(S)-3-bromobutanoic acid with 58% enantiomeric excess146. Asymmetric reactions catalyzed by cyclodcxtrin have been attempted in solution but all of these reactions afforded the products in low optical yields. Exposure of crystalline cyclodextrin complexes to gaseous hydrogen bromide and hydrogen chloride at 20 °C gives better optical yields. 

The Haloform reaction is catalyzed by cyclodextrins in what the authors label as inverse phase transfer catalysis, 25 but the synthetic utility of this variation remains to be seen. An alternative to the use of halogen is a nitroarene catalyzed oxidation of acetophenone with sodium percarbonate or sodium perborate.26 However, the yields of substituted benzoic acids furnished by this method are mediocre (23-73%) in comparison to the conventional Haloform conditions. Likewise, the Haloform reaction of acetone with iodine in liquid ammonia is without synthetic merit (8-12%).27... 

Qi, Q, X She, T Endo and W Zimmermann (2004). Effect of the reaction temperature on the transglycosylation reactions catalyzed by the cyclodextrin glucanotransferase from Bacillus macerans for the synthesis of large-ring cyclodextrins. Tetrahedron, 60,... 

As one of the enzymic reactions, asymmetric synthesis catalyzed by cyclodextrins has been studied in the past, but gave all the products in a low optical yield. We have already found a strong chiral induction for the chlorination of methacrylic acid in the crystalline cyclodextrin complexes. 100 % enantiomeric excess (e.e.) of (-)-2,3-dichloro-2-methyl-propionic acid and 88 % e.e. of its enantiomer were isolated in a- and 3-cyclodextrins, respectively. This paper describes asymmetric addition of gaseous halogens and hydrogen halides in the crystalline complexes comprising trans-cinnamic acid as a reactant and a- or 3-cyclodextrin as chiral matrix. Asymmetric bromination of menthyl cinnamate and of salts from the acid and several chiral amines have been reported, but gave low chiral inductions up to 2 16 % e.e.. 

A branched cyclodextrin, 6-0-a-maltosyl cyclodextrin (G2-CD), was produced from a-D-maltosyl fluoride and a cyclodextrin by the transglycosylation reaction catalyzed by pullulanase or isoamylase [100, 101]. 

T. Furukl, F. Hosokawa, M. Sakurai, Y. Inoue and R. Chujo, Microscopic medium effects on a chemical reaction. A theoretical study of decarboxylation catalyzed by cyclodextrins as an enzyme model, J. Am. Chem. Soc., 115 (1993) 2903. 

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