Polystyrene-supported chiral Brønsted acids for the catalytic production of enantiopure compounds in continuous flow

Chiral Brønsted acids are emerging as very powerful and versatile enantioselective organocatalysts. Ureas, thioureas, squaramides and phosphoric acids are, perhaps, the most popular, with many others being developed. Given the good results obtained in solution, some authors have studied their heterogenization with the aim of reusing and recycling these solid-supported catalysts. The most successful ones have led to the implementation of continuous flow processes. These latter cases are highlighted in this article.