One of the main challenges of this century is the design of sustainable processes, which are not only more economical but also more benign towards the environment. Hence, efficiency and selectivity are critical and catalysis is now involved in the production of more than 80 % of the fine chemicals produced on Earth. In particular, heterogeneous catalysts are widely involved in industrial processes as they enable recycling and continuous processes. In many cases, no leaching is detectable, which facilitates the purification steps which often account for more than 75 % of the energy and solvent cost.Molecular catalysis (organocatalysis) has recently emerged as a powerful tool for bond formation, especially for enantioselective reactions. [1,2] Chirality often arises from natural derivatives, such as alkaloids, carbohydrates, or amino acids. In the case of amino acids, proline has traditionally been the most efficient organocatalyst. [3] Used for enantioselective aldolization, [3][4][5] Michael addition, [6,7] Mannich, [8,9] amination, [10] and Diels-Alder reactions, [11] this amino acid leads to excellent yields and enantiomeric excesses. However, despite its efficiency and low cost, high catalyst loading is often required for high conversions. Furthermore, the workup of such reactions is often a longwinded process, due to the need for DMSO as a solvent.Consequently, it is of great importance to design a way of recycling proline and, more generally, organocatalysts. [1,12] Heterogenization of homogeneous catalysts appeared to be a promising method, as it allowed for good recyclability with simple workup by filtration and washing. The most classical approach relied on the use of polymer-derived ligands. However, kinetics were affected by this treatment as reaction occurred only at the surface of the generated particles. Hence, the steric hindrance generated less efficiency in the transformation, leading to lower enantiomeric excesses.Herein, we describe an approach based on organicinorganic hybrid materials as solid organocatalysts. We directed our research towards layered compounds, such as montmorillonites (MMT). These 2:1 phylosilicates have a global negative charge and entrap metal cations such as sodium or calcium. Classically, these cations can be exchanged with others, to afford the assembly some interesting catalytic properties. Mostly, metal cations have been exchanged and the layered materials used directly in catalysis. [13] As such, palladium(II)-ex-changed clays can catalyze Heck reactions. Other exchanged clays have been prepared, mostly with embedded polymeric structures. We, however, sought to exchange the embedded sodium cation with the conjugated acid from proline ( Figure 1).
