Tailor-Made POLITAG-Pd0 Catalyst for the Low-Loading Mizoroki–Heck Reaction in γ-Valerolactone as a Safe Reaction Medium

Abstract

In this contribution, we have reported our study on the fine-tuned design and synthesis of new POLITAGs-Pd0 (POLymeric Ionic TAG) catalytic systems with the intention of defining highly efficient heterogeneous palladium catalysts stabilized by ionic tags able to operate at a very low loading while being fully recoverable/reusable. By varying both the support and the ratio between the metal and immobilized ionic tag, we have accessed five different heterogeneous catalytic systems that have been fully characterized (EA, XPS, TEM, and HR-TEM) to investigate their morphological differences. The catalytic efficiency of the newly prepared POLITAGs-Pd0 materials was then tested and compared in the representative Mizoroki–Heck cross-coupling reaction, a universally investigated and widely useful process. A close correlation between the catalyst support and catalytic performances has been highlighted. The best system POLITAG-Pd0-HM features a high TOF value (26,786 h–1), affording the final products in high isolated yields by using as little as only 0.0007 mol % of Pd. Moreover, this high catalytic activity coupled with the use of γ-valerolactone (GVL) as a green reaction medium has led to the definition of a very efficient waste-minimized protocol. The newly designed catalyst has been utilized in the representative synthesis of Amiloxate, a widely used sunscreen agent, that could be prepared with negligible metal contamination and very low E-factor.