Asymmetric catalysis overview

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. 

Asymmetric catalysis is a vital and rapidly growing branch of modern organic chemistry. Within this context, Ti- and Zr-based chiral catalysts have played a pivotal role in the emergence of a myriad of efficient and enantioselective protocols for asymmetric synthesis. In this chapter, a critical overview of enantioselective reactions promoted by chiral Zr-based catalysts is provided. Since an account of this type is most valuable when it provides a context for advances made in a particular area of research, when appropriate, a brief discussion of related catalytic asymmetric reactions promoted by non-Zr-based catalysts is presented as well. 

For a general overview of recent advances in this area, see Comprehensive Asymmetric Catalysis (Eds. E. N., Jacobsen, A. Pfaltz, H. Yamamoto), Springer, Berlin, 1999. 

For an overview of the application of enantioselective catalysis in fine chemicals production, see (a) Blaser, H.U., Spindler, F. and Studer, M. (2002) Applied Catalysis A General, 221, 119 (b) Blaser, H.U. and Schmidt, E. (eds) (2003) Large-Scale Asymmetric Catalysis, Wiley-VCH Verlag GmbH, Weinheim, p. 1. 

A very interesting overview and discussion of criteria relevant to industrial catalytic processes is given in H. U. Blaser, E. Schmidt in Asymmetric Catalysis on Industrial Scale (Eds H. U. Blaser, E. Schmidt) Wiley-VCH, Weinheim, 2004, pp. 1 fF. 

Table 2.14 gives an overview of industrial processes using asymmetric catalysis, including examples both of asymmetric hydrogenation and other types of reactions, as well as of the use of biocatalysts for the reaction. Selected chiral ligands used in asymmetric catalytic reactions are also shown in the table. 

For a general overview of the reduction of imines, see the following (a) Morrison, J.D. (1983) Asymmetric Synthesis, vol. 2, Academic, New York (b) Noyori, R. (1994) Asymmetric Catalysis in Organie Synthesis, John WUey Sons, New York (c) Ojima, I. (2000) Catalytic Asymmetric Synthesis, 2nd edn, John WUey Sons, New York ... 

With Comprehensive Asymmetric Catalysis we hope to fill this gap. Comprehensive means that all important classes of enantioselective catalytic transformations are covered but it does not imply an extensive lexicographic compilation of examples. The aim was a concise and readable overview of the field, providing a clear picture of the state of the art. The reader should be able to recognize the scope and limitations of a specific catalyst or method and find the pertinent references for a more detailed bibliographic study. The electronic version with reaction and substructure search options should be particularly useful for this purpose. 

This chapter has presented an overview of applications of DNA in metal ion catalysis. Three general approaches were outlined metal-dependent DNAzymes, DNA-directed and templated catalysis, and DNA-based asymmetric catalysis. 

Remarkably, an overview on aldol reactions with transition metal enolates published in 1991 refers to a single asymmetric catalysis with a late transition metal, the gold-catalyzed reaction of methyl isocyanoacetate with aldehydes cf. Paterson, I. (1991) in Comprehensive Organic Synthesis (eds B.M. Trost and... 

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