Water in asymmetric organocatalytic systems: a global perspective

Abstract

Asymmetric organocatalysis often operates under near ambient conditions, which means it is air and moisture compatible. However, in many examples water is indeed necessary for achieving excellent catalytic results. Ranging from the addition of small amounts of water to a reaction, to complex catalytic systems in the presence of water as the only reaction medium, this review offers an illustrative classification of the uses of water in asymmetric organocatalysis.

Organocatalysis in aqueous media

“…The incentive for this review is to evaluate the potential of organocatalysis in biological settings and to structure the literature on organocatalysis in water. We anticipate to complement existing reviews [11][12][13][16][17][18][19][20] by establishing a comprehensive overview of aqueous phase organocatalysis, discussing potentially interesting organocatalytic bond-making and breaking reactions for biological settings. Each organocatalytic activation mode will be discussed regarding mechanism, history, noteworthy examples, and where relevant a comparison with enzymatic catalysis.…”

Enabling protein-hosted organocatalytic transformations

“…In fact, taking into account the aqueous reaction medium, physiological pH (near 7.4) and temperature (near 37 C), 20 many of the reported organocatalysts do not function under biocompatible conditions. 8,10,17,[21][22][23][24][25][26][27][28][29][30][31] These boundaries vastly narrow the number of organocatalytic reactions applicable and, in response, efforts have been made to overcome limitations related to biocompatibility. 17,32,33 The use of proteins to host organocatalysts To enhance the biocompatibility of organocatalysis, biomolecules including DNA, RNA and proteins can be used to host the reactions.…”

“…16a) were prepared via either copper-catalysed azide-alkyne cycloaddition or amide bond coupling reactions. 39 These catalysts can be broadly segregated into three types: MacMillan-like imidazolidinones (16)(17)(18)(19), prolines (20,21) and pyrrolidines (22,23), and their ability to catalyse the Michael addition of nitromethane to aromatic a,b-unsaturated aldehydes was tested (Fig. 16b).…”

An efficient dynamic asymmetric catalytic system within a zinc-templated network

“…was crucial to ensure the activity of the catalytic system, as we have always encountered during the development of organocatalytic Michael and aldol reactions. [20][21][22][23][24][25][26][27] Moreover, our methodology involves the catalyst pre-formation in solution for 1 hour at room temperature before the reaction temperature is set and substrates are added. Otherwise, an induction period is observed before the catalytic activity can be detected (see ESI ‡ for details).…”