A Pd(II)-Functionalized Covalent Organic Framework for Catalytic Conjugate Additions of Arylboronic Acids to beta,beta-Disubstituted Enones

A palladium(II)-functionalized covalent organic framework (Pd@TpBpy COF) constructed from 1,3,5-triformylphloroglucinol (Tp) and [2,2 '-bipyridine]-5,5 '-diamine (Bpy) is reported as a recyclable catalyst for conjugate additions in aqueous media. Additions of an array of stereoelectronically diverse arylboronic acid nucleophiles to beta,beta-disubstituted enones form a variety of ketones containing benzylic all-carbon quaternary centers in up to 92 % isolated yield. Studies on the recyclability of Pd@TpBpy COF show this catalyst remains active through at least 7 cycles and shows superior stability to related MOF catalysts with bipyridine linker units.