Biomass-Derived Solvents for Sustainable Transition Metal-Catalyzed C–H Activation

Abstract

Transition metal-catalyzed C–H activation has emerged as an increasingly powerful strategy in molecular syntheses and a particularly attractive alternative to classical methods of cross-couplings. During the recent years, significant focus has been dedicated to further improve the sustainable nature of the C–H activation approach. As solvents represent a major portion of organic pollution caused by chemical syntheses, a range of nontoxic, biobased, sustainable solvents have been developed to substitute for common organic reaction media. In this review, we present a general perspective of biomass-derived solvents for transition metal-catalyzed C–H activation reactions and their unique potential for chemical syntheses up to January 2019.

Glycerol: An Optimal Hydrogen Source for Microwave-Promoted Cu-Catalyzed Transfer Hydrogenation of Nitrobenzene to Aniline

“…One way to pursue green synthesis is to improve the sustainable nature of the solvents, as they are directly responsible for the major environmental drawback generated by chemical processes. The use of bio-based and eco-friendly alternative solvents (Gandeepan et al, 2019) has been developed and evaluated over recent decades. Glycerol (1,2,3-propanetriol) is a common natural solvent that is rich in functionalities and is obtained in very large amounts as a co-product in biodiesel production (Cintas et al, 2014;Sudhakar et al, 2016).…”

Exploration of New Biomass‐Derived Solvents: Application to Carboxylation Reactions

“…[15] Analysiso ft he influence of various parameters on the outcomeo ft he reactionw ere conducted on 4methylstyrene 1a using 2MeTHF as as olvent, which already provedt ob easuitable media for reactions involving organometallics (Table 1). [2,4,5] Carefule x-…”

“…[4] The main biomass-derived solvents used in organic synthesis today are glycerola nd its acetals,s everal low-meltingm ixtures of carbohydrates, esters of lactic acid andg luconic acid, 2methyltetrahydrofuran (2MeTHF), cyrene (Cyr), limonene (Lim), p-cymene (Cym), and g-valerolactone (GVL;F igure 1). [2,4,5] The polar protic solvents like glycerol, carbohydratesa sw ell as esters of lactic acid and gluconic acid are mainly used in condensation reactionsa nd have found limited application in transformations involvingo rganometallics. [4] The polar aprotic (2MeTHF,G VL, Cyr)a nd nonpolara protic (Lim, Cym) solvents are far more popular and have been used for many classical transformations including transition metal (TM)-catalyzed cross-couplings [2, 4, 5c] and several CÀHa ctivations.…”

Microwave-Assisted Protocol for Green Functionalization of Thiophenes With a Pd/β-Cyclodextrin Cross-Linked Nanocatalyst

“…The direct functionalization of otherwise inert C-H bonds has recently emerged as a viable alternative (Gandeepan et al, 2019) to traditional cross-coupling reactions, and is a more sustainable approach to transition-metal-catalyzed organic reactions. This approach avoids the pre-functionalization of starting materials and makes C-H activation even more appealing from the viewpoints of high atom and step economy, and high efficiency (Crabtree and Lei, 2017;Meyer et al, 2019).…”

“…Furthermore, achieving regioselective C-H activation is highly challenging as aromatic compounds typically contain multiple C-H bonds. For this reason, the development of new methods for the sustainable synthesis of bi-heteroaryl scaffolds for use as the privileged π-conjugated cores of bioactive compounds, and as functional materials (Ackermann et al, 2009;Gandeepan et al, 2019) is an ongoing challenge for organic chemists. Although ligand-less protocols with low catalyst loadings have recently been developed by Doucet et al, the reaction is still hampered by its harsh conditions and the, up to, 20 h required for completion (Roger et al, 2009).…”