The coupling of CO2 with diols promoted by organic dual systems: Towards products divergence via benchmarking of the performance metrics

Abstract

Herein, we propose a critical study balancing two metal-free dual activating systems, namely DBU/EtBr and TEA/TsCl, for the coupling of CO2 with 1,x-diols to afford (a)cyclic carbonates. In-situ ATR-IR monitoring correlated with DFT calculations led to mechanism propositions for the model formation of propylene carbonate from propylene glycol. Kinetics upon various experimental conditions were established for the first time, leading to an optimized synthetic protocol. The substrates scope was then investigated and selectivities toward the formation of cyclic or linear carbonates were correlated to the dual activating system and the diol structure. By choosing the suitable organic dual activating system, one is able to control the product selectivity to substituted ethylene-or trimethylene carbonate and/or acyclic compounds, providing a powerful tool to synthesize CO2-based precursors that are highly relevant for organic and polymer chemistry from ubiquitous building blocks.

En Route to CO2-Based (a)Cyclic Carbonates and Polycarbonates from Alcohols Substrates by Direct and Indirect Approaches

“…Nevertheless, with 1,4-diols, non-negligible amounts of oligomers were noted, possibly due to the poor stability of 7-membered cyclic carbonates in basic conditions or a competition between the cyclization and the polymerization. In the same manner, a critical study balancing two metal-free dual activating systems, namely DBU/EtBr and TEA/TsCl, was recently proposed for the coupling of CO 2 with 1,x-diols to afford (a)cyclic carbonates [87]. In situ ATR-IR monitoring correlated with DFT calculations was performed to investigate the mechanism and reaction kinetics under various experimental conditions, leading to an optimized synthetic protocol.…”

Exovinylene Cyclic Carbonates: Multifaceted CO2‐Based Building Blocks for Modern Chemistry and Polymer Science

“…The great availability of oxiranes of petro‐ or bio‐based origin gives access to a large library of cyclic carbonates with diverse structures and functionalities. The second approach involves the challenging condensation of CO 2 with polyols into five‐ to eight‐membered cyclic carbonates (Scheme 1b) [17–20] . Although potentially the most interesting in terms of the valorization of natural polyols (e.g.…”

“…Some strategies have been developed to partly overcome this problem, notably by activating the alcohol using metal‐based catalysts in combination with dehydrating agents, [20] or by using bases (tertiary amine or superbases) in combination with alkylating agents (e.g. alkyl halides, sulfonyl halides) [18, 19] . Nonetheless, these processes require harsh conditions and release considerable amounts of waste, rendering them not sustainable.…”

“…The second approach involves the challenging condensation of CO 2 with polyols into five-to eightmembered cyclic carbonates (Scheme 1b). [17][18][19][20] Although potentially the most interesting in terms of the valorization of natural polyols (e.g. glycerol, sorbitol), this second approach remains less explored.…”

“…alkyl halides, sulfonyl halides). [18,19] Nonetheless, these processes require harsh conditions and release considerable amounts of waste, rendering them not sustainable. The third route provides α-exovinylene cyclic carbonates (αCCs) by the carboxylative coupling of CO 2 to propargylic alcohols (Scheme 1c).…”