A green access to supported cinchona alkaloid amide catalysts for heterogeneous enantioselective allylsilylation of aldehydes and process intensity evaluation in batch and flow

Abstract

We report herein a new class of polystyrene-supported cinchona alkaloid amide catalysts for enantioselective allylation of various aldehydes using allyltrichlorosilane under both batch and continuous flow conditions. The supported catalyst was synthesized using an environmentally benign coupling agent with a surfactant in aqueous media. Under batch conditions, consistently high yields and enantioselectivity were obtained for the allylation of aliphatic aldehydes with recycling and reuse of the catalyst for more than 10 runs. Subsequently, this catalytic system was successfully implemented into a packed bed flow reactor with similar efficiency and enantioselectivity. While flow is a viable option, the batch methodology has better potential for application at a larger-scale setting upon the comparison of space-time yield and catalyst loadings. With the sustainable synthesis and great recyclability of our polymeric catalyst, this methodology holds great potential for the large-scale delivery of valuable enantiopure homoallylic alcohols.

Keywords

• Cinchona alkaloids
• Supported catalyst: amide coupling
• Flow chemistry
• Catalyst recyclability