Lewis basic ionic liquids-catalyzed synthesis of 5-aryl-2-oxazolidinones from aziridines and CO2 under solvent-free conditions

Abstract

A series of easily prepared Lewis basic ionic liquids were developed as recyclable and efficient catalysts for selective synthesis of 5-aryl-2-oxazolidinones from aziridines and CO 2 without utilization of any organic solvent or additive. Notably, high conversion, chemo-and regio-selectivity were attained when 1-butyl-4-aza-1-azaniabicyclo[2.2.2]octane bromide ([C 4 DABCO]Br) was used as the catalyst. Furthermore, the catalyst could be recycled over four times without appreciable loss of catalytic activity. The effects of the catalyst structure and various reaction parameters on the catalytic performance were investigated in detail. This protocol was found to be applicable to a variety of aziridines producing the corresponding 5-aryl-2-oxazolidinones in good yields and excellent regioselectivities. Therefore, this solvent-free process thus represents an environmentally friendly process for ionic liquid-catalyzed conversion of CO 2 into value-added chemicals. A possible catalytic cycle for CO 2 activation induced by nucleophilic tertiary nitrogen of the ionic liquid was proposed, based on studies using in situ FT-IR spectroscopy under CO 2 pressure.

Recent applications of aziridine ring expansion reactions in heterocyclic synthesis

“…A number of catalysts are known in literature to ease the reaction. Some of these involve quaternary ammonium bromide-functionalized polyethylene glycol, 101 zirconyl chloride, 102 alkali metal halide, 103 Lewis basic ionic liquids, 104 protic onium salt, 105 polyethylene glycolfunctionalized phosphonium salts, 106 DBN, 107 polyethylene glycol functionalized ionic liquids, 108 2,2',2''-terpyridine, 109 and mesoporous zirconium phosphonates. 110 A very few selected examples are described in succeeding paragraphs.…”

Sustainable conversion of carbon dioxide: the advent of organocatalysis

“…This may help to identify, where possible, improvements that lead to a more widespread use of organocatalysts in CO 2 conversion. Other excellent reviews focusing on the use of hetero-and/or homogenous catalyst systems have recently appeared, 4,[7][8][9][10]18,19,[39][40][41][42] and may serve as a reference point.…”

“…As such, contemporary chemists are facing a huge challenge to develop more sustainable alternatives for chemical production. Carbon dioxide is a waste product from all combustion processes and represents a potential and alternative carbon feed stock 1,2 for the preparation of a variety of useful chemicals including MeOH, 3,4 urea, 5 lactones, 6 various heterocycles, [7][8][9][10][11] biodegradable polymers, [12][13][14][15][16] and carboxylated structures [17][18][19][20][21] among others. [22][23][24] In particular, direct CO 2 utilisation for the preparation of polycarbonates, poly(ether)carbonates and polyurethanes is a viable technology to access novel tailor-made CO 2 -based materials.…”

Organic Base-Catalyzed C–S Bond Construction from CO2: A New Route for the Synthesis of Benzothiazolones

“…On the other hand, when the pressure was higher than 5 MPa, the concentration of CO 2 in the reaction phase was high enough. Thus, higher CO 2 pressure had almost no contribution to the reaction rate, while possibly decreasing the concentration of 2-aminothiophenol in the vicinity of the catalyst, which would retard the interaction, thus resulting in a low efficiency [42][43][44]. Therefore, 5 MPa was deemed a suitable CO 2 pressure.…”