CO2 promoted synthesis of unsymmetrical organic carbonate using switchable agents based on DBU and alcohols. (10th July 2018)

• Record Type: Journal Article
• Authors: Gu, Qingwen; Fang, Jian; Xu, Zichen; Ni, Wenxiu; Kong, Kang; Hou, Zhenshan
• Is Part Of: New journal of chemistry. Volume 42:Number 15(2018)
• Page Start: 13054
• Page End: 13064
• Publication Date: 2018-07-10
• Subjects: Chemistry -- Periodicals; Chimie -- Périodiques; 540
• DOI: 10.1039/c8nj01638k
• Languages: English
• ISSNs: 1144-0546

Abstract

Abstract : Transesterification can be accelerated under pressurized CO2 and satisfactory activity and selectivity to unsymmetrical organic carbonate can be obtained. Abstract : 1, 8-Diazabicyclo[5.4.0]undec-7-ene (DBU) is an effective nucleophilic catalyst for the transesterification of dimethyl carbonate (DMC) with various alcohols and amines, which afforded unsymmetrical organic carbonate and carbamate. It was observed that the transesterification was accelerated under pressurized CO2 in this work. The activity is very high and the best result (89% conversion with 98% selectivity to unsymmetrical carbonate) was obtained for the DBU/alcohol/DMC/CO2 system. The addition of CO2 to DBU/ethanol generated the DBU cation salt, [DBUH][OCOOCH2 CH3 ], which dissociated more favorably under increasing reaction temperature even under pressurized CO2 . The salt could also help to activate DMC by H-bond interaction. The reaction system can be extended easily for the catalytic synthesis of carbamates from amines and DMC. After the reaction, the salt was separated from the reaction mixture and DBU can be recovered by the feasible thermal decomposition, offering a straightforward strategy for the recycling of DBU. On the basis of these results, a plausible mechanism involving the role of both DBU and CO2 has been proposed.