Supramolecular catalysis is a rapidly expanding discipline which has benefited from the development of both homogeneous catalysis and supramolecular chemistry. The properties of classical metal and organic catalysts can now be carefully tailored by means of several suitable approaches and the choice of reversible interactions such as hydrogen bond, metal–ligand, electrostatic and hydrophobic interactions. The first part of these two subsequent reviews will be dedicated to catalytic systems for which non-covalent interactions between the partners of the reaction have been designed although mimicking enzyme properties has not been intended. Ligand, metal, organocatalyst, substrate, additive, and metal counterion are reaction partners that can be held together by non-covalent interactions. The resulting catalysts possess unique properties compared to analogues lacking the assembling properties. Depending on the nature of the reaction partners involved in the interactions, distinct applications have been accomplished, mainly (i) the building of bidentate ligand libraries (intra ligand–ligand), (ii) the building of di- or oligonuclear complexes (inter ligand–ligand), (iii) the alteration of the coordination spheres of a metal catalyst (ligand–ligand additive), and (iv) the control of the substrate reactivity (catalyst–substrate). More complex systems that involve the cooperative action of three reaction partners have also been disclosed. In this review, special attention will be given to supramolecular catalysts for which the observed catalytic activity and/or selectivity have been imputed to non-covalent interaction between the reaction partners. Additional features of these catalysts are the easy modulation of the catalytic performance by modifying one of their building blocks and the development of new catalytic pathways/reactions not achievable with classical covalent catalysts.

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Supramolecular catalysis. Part 1: non-covalent interactions as a tool for building and modifying homogeneous catalysts.

Over the last decade, with the surge in the development of organocatalysis, many processes involving chiral ion pairs have emerged as powerful tools in the design of new efficient organocatalysts. This tutorial review focuses on the recent evolutions of these organocatalytic systems in which both anionic and cationic parts are working in a cooperative fashion in order to develop unique catalytic processes which outperform the existing approaches. In this respect, chiral ion pairs opened new avenues in the design of bifunctional organocatalysts by means of combinatorial approaches.

Recent advances in cooperative ion pairing in asymmetric organocatalysis.

In recent years, enantioselective cooperative catalytic reactions, wherein two catalysts work simultaneously to form products which cannot be obtained by the use of a single catalyst alone, have attracted considerable attention. This review focuses on this emerging field, with particular emphasis on mechanistic aspects, which will help readers to understand the role of each catalyst.

Enantioselective cooperative catalysis

A general and efficient biomimetic method for the synthesis of aldimines from aldehydes and compounds bearing the NH2 group in the presence of pyrrolidine as a catalyst has been developed. These organocatalytic reactions, based on the application of the concept of nucleophilic catalysis, proceed with outstanding yields in the absence of acids and metals under simple conditions and minimum experimental manipulation. The method has been mainly applied to the synthesis of N-sulfinyl and N-sulfonyl imines, but its general validity has been proven with the preparation of representative N-phosphinoyl, N-alkyl, and N-aryl imines. These unprecedented reactions, which presumably occur via iminium activation without requiring acidic conditions, are an interesting and competitive alternative to the classical methods for preparing aldimines.

A general aminocatalytic method for the synthesis of aldimines.

This Minireview focuses on asymmetric reactions mediated by two distinct chiral catalysts (chiral multiple catalysis). Initially, this approach appears unconventional, but indeed it allows a fast multidimensional optimization and fine-tuning of the catalytic system required to perform a given transformation. Herein, this emerging concept is presented and its potential applications are highlighted.

Multiple catalysis with two chiral units: an additional dimension for asymmetric synthesis.

Synergic asymmetric organocatalysis (SAOc) of Cinchona alkaloids and secondary amines in the synthesis of bicyclo[2.2.2]octan-2-ones.

The O-trimethylsilylated α,α-diphenylprolinol-catalyzed addition of aldehydes to cyclic unsaturated enones is described. The apparently unusual stereochemical outcome is discussed.

Enamine‐Mediated Addition of Aldehydes to Cyclic Enones

A synergistic effect between chiral secondary and tertiary amines gives access to bicyclo[2.2.2]octan-2-ones with up to 90% ee and >10 : 1 dr.

Synergic Asymmetric Organocatalysis (SAOc) of Cinchona Alkaloids and Secondary Amines in the Synthesis of Bicyclo[2.2.2]octan-2-ones.

It is found that the prolinol shown in the scheme efficiently promotes the asymmetric addition of aldehydes to the cyclohexenone (I).

Valerio Visca

Papers

Synergic asymmetric organocatalysis (SAOc) of Cinchona alkaloids and secondary amines in the synthesis of bicyclo[2.2.2]octan-2-ones.

Enamine‐Mediated Addition of Aldehydes to Cyclic Enones

Synergic Asymmetric Organocatalysis (SAOc) of Cinchona Alkaloids and Secondary Amines in the Synthesis of Bicyclo[2.2.2]octan-2-ones.

Enamine-Mediated Addition of Aldehydes to Cyclic Enones.