Mechanisms in aminocatalysis

Abstract

The mechanisms of the α-, β- and γ-functionalisations of aldehydes and α,β-unsaturated aldehydes by secondary amines are presented and discussed.

p‐Nitrophenyl Ethylthioester in Enantioselective Organocatalytic Michael Additions: Different Behaviour of β‐Aryl and β‐Alkyl Enals

“…General Methods and Materials: NMR spectra were acquired using CDCl 3 (12 g), in EtOH (250 mL) followed by heating or treatment with a solution of KMnO 4 (1.5 g), K 2 CO 3 (10 g), and 10 % NaOH (1.25 mL) in H 2 O (200 mL). Mass spectra were recorder in positive electrospray ionisation (ESI+) or electron impact ionisation (EI).…”

“…Because enantioselective organocatalysis involving iminium activation [2] provides an excellent procedure for the incorporation of nucleophiles to the β-position of α,β-unsaturated aldehydes, [3] the use of synthetic equivalents of 2-phenylacetic acids as nucleophiles in these processes is very promising for the preparation of highly functionalized 2-phenylacetic acids (Scheme 1). Scheme 1.…”

Stabilization of Proline Enamine Carboxylates by Amine Bases

“…This is well illustrated by the versatility and wide range of different transformations that have been developed in the last decade. A number of theoretical [4] and experimental mechanistic studies [5] for these systems are now available. However, to promote specific reactions the application of dual or cooperative catalyst combinations [6] or the use of (co-catalytic) additives is slowly emerging because this often can prove beneficial for tuning both the reactivity and selectivity of existing catalytic systems.…”

A Simple Recipe for Sophisticated Cocktails: Organocatalytic One‐Pot Reactions—Concept, Nomenclature, and Future Perspectives

“…In 2009, Krause, Alexakis, and coworkers showed that amino- [4] and gold catalysis, [20] two current hot topics in the field of catalysis, could be combined effectively in a two-step reaction sequence consisting of an initial organocatalyzed syn-selective conjugate addition to nitroenynes 27, followed by a gold-catalyzed acetalizationcyclization of 29 to give highly enantiomerically enriched tetrahydrofuranyl ethers 28 (Scheme 6). [21] When the two reactions were performed as separate steps, excellent stereoselectivities were observed, and the yields reached 64-76 % for the overall transformation.…”

“…As one of the major hot topics in organic chemistry throughout the past decade, asymmetric organocatalysis [4] has introduced new perspectives with regard to the design and application of one-pot processes in enantioselective transformations. [5] Marked by its robust nature, organocatalysis is probably the most condition-tolerant method within the modern toolbox of asymmetric catalysis.…”