Asymmetric organocatalysis

Berkessel, A. and Crdger, H. (eds)(2004) Asymmetric Organocatalysis, Wiley-VCH Verlag CmbH, Weinheim. 

Even if organocatalysis is a common activation process in biological transformations, this concept has only recently been developed for chemical applications. During the last decade, achiral ureas and thioureas have been used in allylation reactions [146], the Bayhs-Hillman reaction [147] and the Claisen rearrangement [148]. Chiral organocatalysis can be achieved with optically active ureas and thioureas for asymmetric C - C bond-forming reactions such as the Strecker reaction (Sect. 5.1), Mannich reactions (Sect. 5.2), phosphorylation reactions (Sect. 5.3), Michael reactions (Sect. 5.4) and Diels-Alder cyclisations (Sect. 5.6). Finally, deprotonated chiral thioureas were used as chiral bases (Sect. 5.7). 

Asymmetric organocatalysis in solid-phase chemistry has been recently reviewed [280],... 

The field of asymmetric organocatalysis has a longstanding history that begins in the early twentieth century (see timeline in Figure 11.2). 

While the studies outlined in Eqs. (11.1)-(11.8) summarize the most important frontiers for metal-free synthesis, they also highhght a common limitation for the organocatalysis field. To date, there remain relatively few (less than 10) activation mechanisms that have been established to be amenable to organic catalysis. Accordingly, a primary objective for the advancement of the field of asymmetric organocatalysis has been the design and/or development of concepts that enable organic substrates to function as catalysts for a wide variety of new and established reactions. 

Since 2000, the field of asymmetric catalysis has bloomed extensively (and perhaps unexpectedly) with the introduction of a variety of metal-free catalysis concepts that have collectively become known as organocatalysis. Perhaps more impressive... 

Berkessel A, Groger H (2005) Asymmetric Organocatalysis. Wiley, Weinheim... 

Keywords Asymmetric organocatalysis Bifunctional catalyst Brpnsted base Chiral scaffold Cinchona akaloid Cyclohexane-diamine Guanidine... 

The nitroaldol reaction, particularly involving ketones has been relatively unexplored in the field of asymmetric organocatalysis. Employing cupreines and cupreidines as catalysts, Deng [63] presented an enantioselective nitroaldol reaction of a-ketoesters... 

The preparation of stereochemically-enriched compounds by asymmetric acyl transfer using chiral nucleophihc catalysts has received significant attention in recent years [1-8]. One of the most synthetically useful and probably the most studied acyl transfer reaction to date is the kinetic resolution (KR) of ec-alcohols, a class of molecules which are important building blocks for the synthesis of a plethora of natural products, chiral ligands, auxiliaries, catalysts and biologically active compounds. This research area has been in the forefront of the contemporary organocatalysis renaissance [9, 10], and has resulted in a number of attractive and practical KR protocols. 

Spivey AC, McDaid P (2007) Asymmetric acyl transfer reactions. In Dalko P (ed) Handbook of asymmetric organocatalysis. Wiley, Weinheim, pp 287-329... 

Hydrogen would be the simplest center element. Indeed, chiral Brpnsted acids have emerged as a new class of organocatalysis over the last few years [3-13]. The field of asymmetric Brpnsted acid catalysis can be divided into general acid catalysis and specific acid catalysis. A general acid activates its substrate (1) via hydrogen bonding (Scheme 2, a), whereas the substrate (1) of a specific acid is activated via protonation (Scheme 2, b). 

This protocol complements Akiyama s method which provides P-amino carbonyl compounds as i yn-diastereomers [14], It tolerated aromatic, heteroaromatic, and aliphatic aldehydes. Cyclic ketones, acetone, as well as acetophenone derivatives could be employed. The use of aromatic ketones as Mannich donors was up to that time unprecedented in asymmetric organocatalysis. Rueping et al. independently expanded the scope of the asymmetric Brpnsted acid-catalyzed Mannich reaction of acetophenone [45]. 

---