Synthesis of Cyclic Carbonates from Epoxides and CO₂ under Mild Conditions Using a Simple, Highly Efficient Niobium‐Based Catalyst

Abstract

Like a sore thumb: Niobium stands out among neighboring transition metals for its catalytic performance in the synthesis of cyclic carbonates. Readily available NbCl5 is a very efficient catalyst for the preparation of industrially relevant carbonates at ambient temperature, low CO2 pressure, and low concentrations. DMAP=N,N‐dimethylaminopyridine.

Cycloadditions to Epoxides Catalyzed by Group III–V Transition‐Metal Complexes

“…The NbCl 5 /NBu 4 Br catalyst retained significant activity even at low CO 2 concentration, comparable to that found in "flue" gas (Table 4, entries 1, 2). [34] The catalytic activity of the Nb-based catalytic pairs was observedt ob eh igherf or the case of less sterically hindered epoxidess uch as ethylene and propyleneo xide.I nt he case of more sterically demanding substrates, such as styrene oxide, slightly higher reaction temperatures had to be employed to reach nearly quantitative substrate conversion (Table 4, entries 4, 5). The activity under mild conditions was reported to be low in the case of disubstituted epoxides such as cyclohexene oxide.NbCl 5 /NBu 4 Br was found to be amore efficient catalytic pair than NbCl 5 /DMAP:I nsitu IR investigations highlightScheme7.Yttrium complex 14 used by Yaoand co-workers for the cycloaddition of CO 2 to epoxides.…”

Cycloaddition of Carbon Dioxide and Epoxides using Pentaerythritol and Halides as Dual Catalyst System

“…Following our previous studies on the cycloaddition of CO 2 and epoxides with halide-based catalysts and electrophilic cocatalysts (NbCl 5 , [15] imidazolium-based ionic liquids [16] ), we focused on investigating the reactivity of pentaerythritol (PETT), which is a cheap and non-toxic compound, as cycloaddition catalyst. The catalytic experiments were performed in a Fisher-Porter bottle charged with equimolar amounts of PETT and halide, flushed with argon, filled with PO, and set under a constant pressure of 4 bar CO 2 for 1 min before the reaction mixture was heated to the desired temperature.…”

Green Catalytic Synthesis of Heterocyclic Structures Using Carbon Dioxide and Related Motifs

“…When this bimetallic complex is combined with Bu 4 NBr, an effective mediator for the formation of cyclic organic carbonates is achieved, which allows for ambient coupling between monosubstituted oxiranes and CO 2 . Within the context of effective binary catalysts for cyclic carbonate synthesis under relatively mild conditions (low-energy input), there have been several other interesting reports that will not be discussed here [54][55][56][57][58]. As such, this catalyst based on an earth-abundant, nontoxic metal can be regarded as one of the greenest reported to date.…”