Asymmetric reactions historical perspective

From a historical perspective it is interesting to note that the Nozaki experiment was, in fact, a mechanistic probe to establish the intermediacy of a copper carbe-noid complex rather than an attempt to make enantiopure compounds for synthetic purposes. To achieve synthetically useful selectivities would require an extensive exploration of metals, ligands and reaction conditions along with a deeper understanding of the reaction mechanism. Modern methods for asymmetric cyclopropanation now encompass the use of countless metal complexes [2], but for the most part, the importance of diazoacetates as the carbenoid precursors still dominates the design of new catalytic systems. Highly effective catalysts developed in... 

Historical perspective C. H. Heathcock, Comp. Org. Syn. 2, 133-179 (1991). General review T. Mukaiyama, Org. React. 28,203-331 (1982). Application of lithium and magnesium enolates C. H. Heathcock, Comp. Org. Syn. 2, 181-238 (1991) of boron enolates B. M. Kim etal, ibid. 239-275 of transition metal enolates I. Paterson, ibid. 301-319. Stereoselective reactions of ester and thioester enolates M. Braun, H. Sacha, J. Prakt. Chem. 335,653-668 (1993). Review of asymmetric methodology A. S. Franklin, I. Paterson, Contemp. Org. Syn. 1,317-338 (1994). Cf. Claisen-Schmidt Condensation Henry Reaction Ivanov Reaction Knoevenagel Condensation Reformatskv Reaction Robinson Annulation. 

Although there are two distinctive approaches to enan-tioselective sulfa-Michael reactions—nucleophilic activation of thiols and electrophilic activation of alkenes—the recent emergence of bifunctional catalysts has greatly improved our understanding in the wider perspective of origin of asymmetric induction. A comprehensive review of asymmetric sulfa-Michael reactions by Ender and co-work-ers appeared in 2007 that covered the advances in this field from 1970s to 2005. " The reader is advised to refer this review article for a historical overview. The goal of this section, thus, is to focus on a few selected stereoselectivity issues in the asymmetric sulfa-Michael reactions and to document new advances made from 2005 to the present time. 

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