Continuous-Flow Asymmetric Aldol Addition Using Immobilized Chiral Catalyst on Organogel-Based Porous Monolith

Continuous-flow reactions using immobilized chiral catalysts are attracting much attention in the field of fine chemical productions. Porous materials can mitigate the mass transfer limitation and undesired steric effects from support materials owing to their large surface area and high porosity. Among them, porous monoliths, which are self-standing materials with interconnected pores with narrow diameters offer high permeability during the continuous-flow operation. Supporting the chiral catalyst on the monolith, asymmetric reaction can be achieved under continuous-flow condition. To date, the continuous-flow reactors with porous monoliths have been developed for chiral catalysis. Herein, we first developed porous organogel monoliths as support for chiral catalyst in continuous-flow reaction. The monolith showed higher catalytic durability than those of batch in asymmetric aldol additions. Detailed studies on continuous-flow conditions and physical properties of the monolith revealed the importance of increasing the gel porosity of the monolith.