One-pot synthesis of optically pure β-hydroxy sulfones via a heterogeneous ruthenium/diamine-promoted nucleophilic substitution-asymmetric transfer hydrogenation tandem process

Abstract

A mesoporous silica-based ruthenium/diamine-functionalized heterogeneous catalyst is prepared through the co-condensation of chiral 4-((trimethoxysilyl)ethyl)phenylsulfonyl-1,2-diphenylethylene-diamine and tetraethoxysilane, followed by complexation with a ruthenium/diamine complex. Its solid-state carbon cross-polarization/magic angle spinning NMR spectrum demonstrates well-defined single-site ruthenium/diamine species, whereas the scanning and transmission electron microscopy images confirm the highly distributed ruthenium active centers on uniformly mesostructured nanoparticles. This heterogenous catalyst displays high catalytic and enantioselective performance in the nucleophilic substitution-asymmetric transfer hydrogenation one-pot enantioselective tandem reactions of α-bromoketones and sodium sulfonates, resulting in various chiral β-hydroxy sulfones with up to 99% enantioselectivity. Furthermore, the recycled heterogeneous catalyst can be reused repeatedly for at least six times, providing a practical approach for the one-pot preparation of chiral β-hydroxy sulfones in an environmentally friendly medium.