Hydrolytic Kinetic Resolution of Terminal Epoxide

Jacobsen developed a powerful method for the preparation of enantiopure terminal epoxides by using the technique of hydrolytic kinetic resolution (HKR) [82, 83]. 

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The hydrolytic kinetic resolution of terminal epoxides catalyzed by the monomer la and dimer lb... 

S,12S)-2,12-Diacetoxytridecane (17) is a component of the female pheromone of pea midges (Contarinia pisi). Kitching synthesized 17 as shown in Scheme 28 by employing Jacobsen s hydrolytic kinetic resolution of terminal epoxides with a (salen)Co(OAc) complex, (S,S)-B [46]. By this reaction bis-... 

Cavazzini, M. Quid, S. Pozzi, G. (2002) Hydrolytic kinetic resolution of terminal epoxides eatalyzed by fluorous chiral Co(salen) complexes. Tetrahedron 58 3943-3949. 

Shepperson, L Cavazzini, M. Pozzi, G. Quici, S. (2004) Fluorous biphasic hydrolytic kinetic resolution of terminal epoxides, J. Fluor. Chem., 125 175-180. 

Annis, D. A. Jaeobsen, E. N. (1999) Polymer supported ehiral Co(salen) complexes synthetie applieations and mechanistic investigations in the hydrolytic kinetic resolution of terminal epoxides., Y. Am. Chem. Soc., 121 4147-4154. 

To investigate the catalytic activity of the materials prepared, hydrolytic kinetic resolution of terminal epoxides such as styrene oxide, 1,2-epoxyhexane, and epi-chlorohydrin was carried out using only water, which acts as a nucleophilic agent... 

Hydrolytic Kinetic Resolution of Terminal Epoxides with Water (Scheme 6.9)... 

This result, caused by the proximity effect between peripheral catalytic sites, can translate into higher or lower catalytic activity of the metallodendrimer in homogeneous catalysis, and is commonly termed the dendritic effect. In the above case, a negative dendritic effect is observed. An interesting example of a positive dendritic effect on catalyst activity was reported by Jacobsen et al. in the hydrolytic kinetic resolution of terminal epoxides by peripherally Co(salen)-substituted PAMAM dendrimers [39]. 

Schaus, S. E., Brandes, B. D., Larrow, J. F., Tokunaga, M., Hansen, K. B., Gould, A. E., Furrow, M. E., Jacobsen, E. N. Highly Selective Hydrolytic Kinetic Resolution of Terminal Epoxides Catalyzed by Chiral (salen)Colll Complexes. Practical Synthesis of Enantioenriched Terminal Epoxides and 1,2-Diols. J. Am. Chem. Soc. 2002, 124, 1307-1315. 

S. E. Schaus, B. D. Brandes, J. F. Larrow, M. Tokunaga, K. B. Hansen, A. E. Gould, M. E. Furrow, E. N. Jacobsen, Highly selective hydrolytic kinetic resolution of terminal epoxides cataly zed by chiral (salen)Co complexes. Practical synthesis of enantioenriched termmal epoxides and... 

When using (rac)-vinylcyclohexane epoxide as a standard substrate (Scheme 4.24), the dendrimer catalysts exhibited significantly higher catalytic activities in the hydrolytic kinetic resolution of terminal epoxides as compared to the monomer or the dimer catalysts. Among the dendrimer catalysts, the first-generation dendrimer catalyst gave the best results and the efficiency of the catalyst on a per-metal basis was in the following order 4-Co(salen)-PAMAM > 8-Co(salen)-PAMAM > 16-Co(salen)-PAMAM. This dendrimer effect was considered to arise from the restricted conformation imposed by the dendrimer structure, which enhanced the... 

Scheme 5.3 Hydrolytic kinetic resolution of terminal epoxides.

Nielsen LPC, Stevenson CP, Blackmond DG et al (2004) Mechanistic investigation leads to a synthetic improvement in the hydrolytic kinetic resolution of terminal epoxides. J Am Chem Soc 126 1360-1362... 

Schaus SE, Brandes BD, Larrow JF et al (2002) Highly selective hydrolytic kinetic resolution of terminal epoxides catalyzed by chiral (salen)Co-III complexes. Practical S5Uithesis of enantioenriched terminal epoxides and 1,2-diols. J Am Chem Soc 124 1307-1315... 

It should be noted that the corresponding Co(salen) complexes have also been used in the hydrolytic kinetic resolution of terminal epoxides, enantioselectivies up to 99% being obtained however these complexes were never used in a two-phase system [30]. 

In particular, for the synthesis of optically pure chemicals, several immobilization techniques have been shown to give stable and active chiral heterogeneous catalysts. A step further has been carried out by Choi et al. [342] who immobilized chiral Co(III) complexes on ZSM-5/Anodisc membranes for the hydrolytic kinetic resolution of terminal epoxides. The salen catalyst, loaded into the macroporous matrix of Anodise by impregnation under vacuum, must exit near the interface of ZSM-5 film to contact with both biphasic reactants such as epoxides and water. Furthermore, the loading of chiral catalyst remains constant during reaction because it cannot diffuse into the pore channel of ZSM-5 crystals and is insoluble in water. The catalytic zeolite composite membrane obtained acts as liquid-liquid contactor, which combines the chemical reaction with the continuous extraction of products simultaneously (see Figure 11.28) the... 

Besides biomimetic complexes, Jacobsen described particularly efficient bis (chromium-salen) catalyst 9 for the asymmetric ring-opening reaction of epoxides with azide (Scheme 9) [42]. The efficiency of this class of catalysts is attributed to a cooperative mechanism, both substrates being activated toward each other by their respective chromium atom. Of note, a less pronounced cooperative effect was initially demonstrated in an intermolecular manner using monomeric Cr(N3)-salen catalyst [43]. Jacobsen also showed that an analogous cooperative mechanism takes place using polymer-supported chiral Co(salen) complexes for the hydrolytic kinetic resolution of terminal epoxides [44, 45]. 

A SALEN-containing catalyst, A,A-bis(3,5-di-tert-butylsalicylidene)-l,2-cyclohexanediamino-cobalt(II), proved to be an efficient catalyst for the hydrolytic kinetic resolution of terminal epoxides (187) and the enantioselective ring opening of meso epoxides (188). The same complex proved to be active in the asymmetric hetero-Diels-Alder reaction (189). 

Chiral (salen)Co catalysts were found to be efficient catalysts for hydrolytic kinetic resolution of terminal epoxides with water [78]. The solvent-free reaction condition with racemic propylene oxide with 0.55 equiv of water and 0.2 mol%... 

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