Organocatalysis Strecker reactions

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). 

Chiral Br0nsted Acids for Asymmetric Organocatalysis 2.3.8 Strecker Reactions... 

A pioneer in the field of the asymmetrie (thio)urea organocatalysis was Eric Jacohsen, who first reported a chiral (polymer-hound) Schiff base thiourea derivative for asymmetric Strecker reactions optimised from parallel synthetic libraries/ These catalysts can be used either in solution or immobilised to a polystyrene resin, with the latter retaining efficiency, after repeated recycling/ The key factors responsible for high enantioselectivities were the presence of bullqr substituents at both the amino acid position and at the 3-position of the aromatic ring (Scheme 19.3). 

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