Asymmetric one-pot reactions using heterogeneous chemical catalysis: recent steps towards sustainable processes
The preparation of optically pure fine chemicals is among the most important and challenging tasks met by organic chemists. Recently, significant efforts have been focused on the development of green and sustainable procedures for the synthesis of these high value-added compounds. Asymmetric heterogeneous catalysis has provided efficient solutions to these challenges. The application of heterogeneous chiral catalysts in one-pot processes combines the advantages of use of these materials with time, material, and energy savings associated with cascade or sequential procedures. This review surveys these asymmetric one-pot reactions reported until July 2017, in which a heterogeneous chemical catalyst has been applied either as a single multifunctional catalyst or in combination with a second catalytically active material. These processes include one-pot procedures catalysed by carefully designed solids obtained by the immobilization of chiral metal complexes, by anchoring chiral organocatalysts, or by modifying catalytic surfaces with optically pure compounds, which may also incorporate uncatalyzed and homogeneously catalysed steps. Methods applying achiral heterogeneous catalysts in combination with soluble chiral chemical catalysts or biocatalysts are also presented. Sophisticated, finely tuned materials have been applied in most of these reactions, which have been discussed along with the main requirements necessary to perform these transformations in a one-pot manner.