A technology platform to chiral amines: selected examples in asymmetric organocatalysis
Organocatalysis makes use of small organic molecules to activate reaction partners and is nowadays an established catalytic platform; in fact, despite the relatively young age, its potential and powerful impact is widely appreciated. Importantly, organocatalysis, along with metal- and biocatalysis, is routinely screened in industry during the selection process to target compounds of interest. Among these, chiral amines are one of the most important class of target molecules in industry. Herein we present selected approaches in organocatalysis to access chiral amines both from academia and industry.
Industry has a wide range of options to access chiral molecules; often, for a number of reasons, the selection of technologies to enantioselectively and efficiently prepare the molecule of interest falls within the realm of asymmetric catalysis. Along with bio- and metal-catalysis, organocatalysis (1) is nowadays recognised as the third pillar in asymmetric catalysis and it is increasingly screened in industry and used in commercial processes (2).
Organocatalysis is governed either by covalent bonds formed between substrates and catalysts or by weaker bonds such as H-bonding or ion-pairing; it encompasses various modes of activation that may be broadly classified as Brønsted bases, Brønsted acids, Lewis bases and Lewis acids (1c). The catalytic cycle can be initiated via a nucleophilic addition of the catalyst to the substrate (Lewis base catalysis) or via deprotonation (Brønsted base catalysis); complementarily, nucleophilic substrates can be activated with Lewis acids via coordination or protonated with Brønsted acids. This allows the chemist to exploit the catalysis for a number of different reactions, through various activation modes, ...