Issue 12, 2023

Mechanistic insights into the Cu(ii)/DBU-catalyzed incorporation of CO2 into homopropargylic amines

Abstract

The mechanisms of Cu(II)/DBU-catalyzed carboxylation of homopropargylic amines with CO2 to construct 6-methylene-1,3-oxazin-2-ones are studied via density functional theory. The calculations suggest that Cu(II) catalysts exhibit a positive effect on the process of intramolecular cyclization, and the catalytic activities of which are determined by their coordination abilities ((DBU)CuCl2 < CuCl2 < [(DBU)CuCl]+). Furthermore, three roles of DBU are revealed in this study: (a) DBU acts as the proton-acceptor to capture a proton of homopropargylic amines. (b) DBU attacks CO2 to form DBU-CO2 as the nucleophilic agent, and then DBU-CO2 assists the H+ shift as the proton shuttle. (c) DBU serves as the ligand replacing one Cl− anion of CuCl2, forming the activated species [(DBU)CuCl]+. Besides, the theoretical study well explains the selectivity of Cu(II)-catalyzed reactions (6- vs. 7-membered cyclization), and the 6-membered products are found to be formed selectively. Overall, our work reproduces the experimental results well and provides an indispensable understanding of CO2-conversion to synthesize various high-value chemicals with the assistance of a catalytic system combining transition-metal catalysts and organic bases.

Graphical abstract: Mechanistic insights into the Cu(ii)/DBU-catalyzed incorporation of CO2 into homopropargylic amines

Supplementary files

Article information

Article type
Paper
Submitted
26 Nov 2022
Accepted
13 Feb 2023
First published
13 Feb 2023

New J. Chem., 2023,47, 5691-5700

Mechanistic insights into the Cu(II)/DBU-catalyzed incorporation of CO2 into homopropargylic amines

B. Yuan, S. Liu, T. Liu, Q. Li, Y. Wang, Z. Guo, X. Guo, H. Huang and R. He, New J. Chem., 2023, 47, 5691 DOI: 10.1039/D2NJ05809J

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