Immobilization of palladium(ii) acetate on a polymer-anchored Schiff base as a new heterogeneous catalyst for three-component one-Pot Mizoroki–Heck coupling via an in situ witting reaction†

Abstract

In this work, 4-((4-methylbenzyl)oxy)benzaldehyde resin-supported Pd^(II)-Schiff base PS@Pd(OAc)₂ was synthesized. FT-IR, XPS, TGA, ICP-MS, and powder XRD established the structure of PS@Pd(OAc)₂. The morphology and distribution of elements on PS@Pd(OAc)₂ were determined using SEM, TEM, and elemental mapping analysis. The heterogenized PS@Pd(OAc)₂ catalyst was found to be efficient in promoting three-component Mizoroki–Heck coupling via an in situ Witting reaction, where (E)-1,2-diphenylethenes were efficiently synthesized from the Witting salt. In this one-pot reaction, this catalyst exhibits a distinct synergistic effect. The significant mass-transfer limitation results from a nonsignificant distribution of active sites amalgamated with the crumpling of catalysts, which facilitates the smooth, easy movement of the reactants and products toward the well-spaced active catalytic sites on the catalyst's surface. These characteristics increase the catalytic activity of PS@Pd(OAc)₂. Moreover, the catalyst was found to be quite robust for this reaction with very little metal leaching; thus, it can be efficiently recycled. Hence, multiple uses were established, and its reusability was proven in this important reaction.