2022 Volume 5 Issue 6

Open Access

INEOS OPEN, 2022, 5 (6), 158–160  Journal of Nesmeyanov Institute of Organoelement Compounds of the Russian Academy of Sciences Download PDF DOI: 10.32931/io2227a

Mixtures of Heterocycles and Iodine as the Catalysts for the Formation
of Organic Carbonates from Epoxides and CO₂

Abstract

Combinations of a series of nitrogen-containing heterocycles with iodine were tested as the catalysts for the synthesis of cyclic carbonates from epoxides and CO₂. It is shown that the systems containing aliphatic substituents are more efficient, the presence of a free NH group has a beneficial effect on the conversion, and the systems with two or more nitrogen atoms are more active.

Key words: heterocycles, iodine, epoxides, CO₂ fixation, organic carbonates.

 

Introduction

Organic carbonates are widely used as fuel additives, polar solvents, including those used in lithium-ion batteries, as well as monomers for the production of polycarbonates and non-isocyanate polyurethanes [1]. One of the convenient approaches to the preparation of organic carbonates is the addition of CO₂ to epoxides [2–4]. Nowadays, the following catalysts are used to promote this reaction: transition metal complexes, ionic liquids, and nonmetallic catalysts such as organic ammonium, imidazolium, and phosphonium salts, in particular those covalently or weakly bound to solid supports [5, 6]. Recently, it has been shown that the catalysts for this process can be drastically simplified to the mixtures of iodine with amines, which give [NR₃I]I systems [7–12]. The efficiency of these catalysts increases when the amine component contains donor aliphatic substituents. The presence of additional hydroxy or amino groups, which can facilitate both the opening of an epoxide ring and the subsequent insertion of CO₂ into the molecule, has an additional cocatalytic effect. Of particular interest for the production of highly efficient catalysts for the addition of CO₂ to epoxides are heterocyclic amines. In this communication, we report on the results of investigation of the catalytic performance of a series of nitrogen-containing heterocycles in combination with iodine in the addition of CO₂ to epoxides.

Results and discussion

Combinations of a series of heterocyclic amines (1–8) with iodine (1 mol %) were tested in the addition of CO₂ to propylene oxide (9a) for 2 h (Scheme 1).