Biomass Waste-Derived Pd–PiNe Catalyst for the Continuous-Flow Copper-Free Sonogashira Reaction in a CPME–Water Azeotropic Mixture

Abstract

Herein, we report on the development of a waste minimization/valorization methodology applied to the representative benchmark Sonogashira cross-coupling reaction performed in a continuous-flow reactor, featuring a continuous-flow downstream membrane organic/aqueous separator to recover medium and products with minimal waste. The protocol is based on the use of a biomass waste-derived heterogeneous Pd-based catalyst, which is obtained from the valorization of urban-waste pine needles (PiNe). In a circular economy approach, the PiNe biomass has been proven to be capable of producing an effective active carbon support for Pd nanoparticle immobilization. In addition, the catalyst has been utilized in an azeotropic mixture formed by industrial wastederived cyclopentyl methyl ether (CPME) and water. Thanks to this combination and with the adoption of flow conditions, high yields of final target products could be accessed with high stability and durability of the catalyst. Final isolation of the products has been realized by setting an in-line liquid−liquid separator in flow, which has also allowed CPME recovery with a significant reduction of the waste generated. The protocol has been applied to the representative preparation of eniluracil, a GSK API.

Biomass-Derived Carbon Materials in Heterogeneous Catalysis: A Step towards Sustainable Future

“…A Pd/PiNe catalyst was used to study the continuous-flow copper-free Sonogashira reaction, enabling a multigram-scale production that not only optimized the recovery and reuse of the catalytic system and reaction media but also reduced the amount of waste created. With an average throughput of 0.95 mmol per hour, the flow reactor demonstrated steady efficiency and negligible metal leaching during its 15 days of continuous operation [129]. Aminosilane-functionalized low-cost mesoporous biomass carbon (BC) from waste radish leaves was synthesized for the first time with a specific surface area of 703.99 m 2 g −1 by Kempasiddaiah and colleagues.…”

POLITAG-M-F as Heterogeneous Organocatalyst for the Waste-Minimized Synthesis of β-Azido Carbonyl Compounds in Batch and under Flow Conditions

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Waste-Minimized Continuous-Flow Synthesis of Oxindoles Exploiting a Polymer-Supported N Heterocyclic Palladium Carbene Complex in a CPME/Water Azeotrope

“…Our research is focused on the development of sustainable synthetic protocols utilizing heterogeneous catalytic systems − and focusing on the design and development of tailor-made polymeric supports for the preparation of immobilized catalysts with specific stability and versatility. − …”