Bio-inspired single-chain polymeric nanoparticles containing a chiral salen TiIV complex for highly enantioselective sulfoxidation in water

A series of bio-inspired single-chain polymeric nanoparticles (SCPNs) containing a chiral salen TiIV complex in their hydrophobic cavity were constructed from the synthesized amphiphilic copolymers of poly(NIPAAm-co-IL/Ti(salen)) (NIPAAm, N-isopropylacrylamide; IL/Ti(salen), vinylimidazolium ionic liquid-modified chiral salen TiIV complex). These SCPNs behaved as enzyme-mimetic catalysts due to compartmentalization and site isolation, mediating enantioselective oxidation of various sulfides in water with excellent yields (90-99%) and enantioselectivities (ee, 88-99%). In particular, the ee values observed for electron-rich substrates (>95% ee) represented the best results so far in titanium-salen systems. Moreover, the catalysts could be easily recovered for steady reuse by thermo-controlled separation due to thermo-responsive properties. This work first constructed titanium-containing biomimetic SCNPs for biocatalysis of enantioselective sulfoxidation in water.