Volume 15, Issue 5 e202201373
Research Article

Dihydroxybenzene-derived ILs as Halide-Free, Single-component Organocatalysts for CO2 Insertion Reactions

Nicola Bragato

Nicola Bragato

Department of Molecular Sciences and Nanosystems, Ca' Foscari University of Venice, Via Torino 155, 30172 Venezia, Italy

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Prof. Alvise Perosa

Prof. Alvise Perosa

Department of Molecular Sciences and Nanosystems, Ca' Foscari University of Venice, Via Torino 155, 30172 Venezia, Italy

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Prof. Maurizio Selva

Prof. Maurizio Selva

Department of Molecular Sciences and Nanosystems, Ca' Foscari University of Venice, Via Torino 155, 30172 Venezia, Italy

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Prof. Giulia Fiorani

Corresponding Author

Prof. Giulia Fiorani

Department of Molecular Sciences and Nanosystems, Ca' Foscari University of Venice, Via Torino 155, 30172 Venezia, Italy

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First published: 30 January 2023
Citations: 2

Graphical Abstract

Magic insertion! We report the sustainable, halide-free synthesis of dihydroxybenzene based ILs which displayed an unprecedent activity as single component catalyst for the selective synthesis of cyclic organic carbonates upon CO2 insertion reaction in terminal and internal epoxides (6 examples, up to 98 % yield and >99 % selectivity). An unusual mechanistic pathway is also proposed.

Abstract

A series of dihydroxybenzene-derived ILs was synthesised via a halide-free, eco-friendly methodology and fully characterized. Their activity as single component catalyst towards synthesis of cyclic organic carbonates (COCs) via CO2 insertion into terminal epoxides was evaluated, observing that methyltrioctylammonium hydroquinolate, [N1888][HYD], was the most active catalyst in the proposed optimized conditions ([N1888][HYD] 10 % mol, T=120 °C, t=6 h, p0(CO2)=2.0 MPa, 12 examples, conversion >99 %, yield up to 98 %). Interestingly, [N1888][HYD] was also an active catalyst for CO2 insertion reactions with cyclohexene oxide (CHO), observing formation of both the COC and polycarbonate product. It is proposed that for p0(CO2)≥1.0 MPa, the catalytically active species is the hemicarbonate derivative of the hydroquinolate anion, active towards epoxide ring opening via an unusual hemicarbonate-alkoxide pathway.

Conflict of interest

The authors declare no conflict of interest.

Data Availability Statement

The data that support the findings of this study are available in the supplementary material of this article.