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

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.

Halide-free pyridinium base binary organocatalyst for the cycloaddition of carbon dioxide to epoxides

“…Considerable research efforts have focused on improving homogeneous catalysts for synthesizing cyclic carbonates. [1][2][3][36][37][38][39][40][41] In such systems, the absence of halide ions, addressing concerns related to their toxicity, corrosion potential in reactors, and lack of environmental friendliness 42,43 have led to the development of catalytic systems devoid of halogen elements. 44 The advancement of halide-free catalysts, aimed at reducing the risk of reactor corrosion associated with halides, has captured widespread attention.…”

“…Considerable research efforts have focused on improving homogeneous catalysts for synthesizing cyclic carbonates. 1–3,36–41 In such systems, the absence of halide ions, addressing concerns related to their toxicity, corrosion potential in reactors, and lack of environmental friendliness 42,43 have led to the development of catalytic systems devoid of halogen elements. 44…”

Diaspore as an efficient halide-free catalyst for the conversion of CO2 into cyclic carbonates

“…27 In another recent report, Bragato et al developed ionic liquids to prepare cyclic carbonates at 120 °C under 2 MPa pressure of CO 2 . 28 The above-mentioned works reported the halide-free synthesis of cyclic carbonates under high pressure. Nevertheless, to our knowledge, there are relatively few reports on halide-free heterogeneous catalysts to produce cyclic carbonates with satisfactory yields under atmospheric pressure.…”