Synthetic Organic "Aquachemistry" that Relies on Neither Cosolvents nor Surfactants

Abstract

There is a growing awareness of the underlying power of catalytic reactions in water that is not limited to innate sustainability alone. Some Type III reactions are catalytically accelerated without dissolution of reactants and are occasionally highly selective, as shown by comparison with the corresponding reactions run in organic solvents or under solvent-free conditions. Such catalysts are highly diversified, including hydrophilic, lipophilic, and even solid catalysts. In this Outlook, we highlight the impressive characteristics of illustrative catalysis that is exerted despite the immiscibility of the substrates and reveal the intrinsic benefits of these enigmatic reactions for synthetic organic chemistry, albeit with many details remaining unclear. We hope that this brief introduction to the expanding field of synthetic organic "aquachemistry" will inspire organic chemists to use the platform to invent new transformations.

Scheme 1. Example of an Enzymatic Reaction of a Water-Insoluble Compound

Figure 1

Schematic images of Type III reactions with catalysts (no cosolvents, no amphiphilic molecules). Yellow shapes represent droplets consisting of reactant(s); capital C indicates a soluble catalyst (blue: soluble in water, red: lipophilic and soluble in suspended droplets), and purple hexagons indicate an insoluble solid catalyst.

Scheme 2. Uncommon Asymmetric 1,6-Borylation under Type IIIc Conditions

Scheme 3. Type IIIc Asymmetric β-Silylation of β-Nitrostyrene