Recent Developments on Supported Hydrogen-bond Organocatalysts

Hydrogen-bond organocatalysts are a family of Brønsted acid organic compounds able to activate electrophilic substrates toward nucleophilic addition through hydrogen bonding interactions. Since the first report using these catalysts, they have been widely exploited in several valuable processes, in general with high activities and selectivities. The immobilization of hydrogen-bond catalysts affords heterogeneous systems which enable different features for a green chemistry approach, such as chemical and mechanical stability, easy work-up and/or reusability. Several kinds of supports have been employed for immobilization while maintaining the advantages of the homogeneous catalysts. In the present review, we have mainly focused our attention in the immobilization of ureas, thioureas and squaramides organocatalysts onto various supports, including polymeric materials, mesoporous silicas, nanoparticles and ionic liquids, and also some copolymerization processes have been described. In addition, the role of these supported organocatalysts published since 2010 on different stereoselective transformations has been evaluated.