Chiral catalysis method

U. Kragl and T. Dwars, The development of new methods for the recycling of chiral catalysis, Trends Biotechnol. 2002, 19, 442-449 (erratum in Trends Biotechnol. 

There are several different approaches to fixing a molecular catalyst into a host material, some of these methods have been reviewed recently by On et al.[881 in 2001 and by De Vos et af.[89] Reviews from the perspective of chiral catalysis appeared in 2002 by Song and Lee,[90] and in 2004 by Li,[91] and noncovalently bound catalytic species on solid supports have been reviewed in 2004 by Horn et al.[92] This section is intended to complement these recent reviews and highlight as well as define the approaches encountered and to update some of the latest developments in this field. 

The quantum chemical modeling of such chiral catalysis has been developed by Nevalainen [33]. An investigation into the origin of the enantioselectivity was also carried out using molecular orbital methods [32]. 

The enantioselective addition of HX to a./i-unsaturated carbonyl compounds under catalysis by optically active bases is known in great detail for systems in which the stereogenic center is created on the ketone skeleton through the connection of X (method ) or on chiral HX1 (method ) by deracemization 167,168. 

In addition to the wide application of click protocol in chemical biology, this highly facile method has also been well established for the development of chiral catalysis to be useful in asymmetric synthesis. A carbohydrate-based ligand 119,... 

Recently, the direct synthesis of i-proHne-functionalized mesoporous silica was reported. The proline-mesoporous silica synthesized by co-condensation method offered a large surface area, high OMS, and tunable length of the pore channel. And also, it could be appHed for chiral catalysis [62, 63]. 

Clearly, there is a need for techniques which provide access to enantiomerically pure compounds. There are a number of methods by which this goal can be achieved . One can start from naturally occurring enantiomerically pure compounds (the chiral pool). Alternatively, racemic mixtures can be separated via kinetic resolutions or via conversion into diastereomers which can be separated by crystallisation. Finally, enantiomerically pure compounds can be obtained through asymmetric synthesis. One possibility is the use of chiral auxiliaries derived from the chiral pool. The most elegant metliod, however, is enantioselective catalysis. In this method only a catalytic quantity of enantiomerically pure material suffices to convert achiral starting materials into, ideally, enantiomerically pure products. This approach has found application in a large number of organic... 

The past thirty years have witnessed great advances in the selective synthesis of epoxides, and numerous regio-, chemo-, enantio-, and diastereoselective methods have been developed. Discovered in 1980, the Katsuki-Sharpless catalytic asymmetric epoxidation of allylic alcohols, in which a catalyst for the first time demonstrated both high selectivity and substrate promiscuity, was the first practical entry into the world of chiral 2,3-epoxy alcohols [10, 11]. Asymmetric catalysis of the epoxidation of unfunctionalized olefins through the use of Jacobsen s chiral [(sale-i i) Mi iln] [12] or Shi s chiral ketones [13] as oxidants is also well established. Catalytic asymmetric epoxidations have been comprehensively reviewed [14, 15]. 

Abstract After an overview of chiral urea and thiourea synthetic methods, this review describes the main applications of urea and thiourea complexes in asymmetric catalysis. Some recent examples of thioureas as catalysts are also presented. Coordination chemistry of ureas and thioureas is briefly discussed. 

Corey, E.J. Helal, C.J. (1998) Reduction of Carbonyl Compounds with Chiral Oxazaborolidine Catalysts A New Paradigm for Enantioselective Catalysis and a Powerful New Synthetic Method. Angewandte Chemie International Edition, 37, 1986-2012. 

Gruttadauria, M., Riela, S., Lo Meo, P., D Anna, F., Noto, R. (2004) Supported Ionic Liquid Asymmetric Catalysis A New Method for Chiral Catalysts Recycling, the Case of ProUne-Catalysed Aldol Reaction. Tetrahedon Letters, 45(32), 6113-6116. 

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