A mechanistic study on coupling of CO 2 and epoxide mediated by guanidine/TBAI catalysts
Density functional theory (DFT) calculations at the M062X-D3/def2-TZVP//M062X-D3/def2-SVP level of theory were employed to reveal the mechanism of the reaction between CO 2 and styrene oxide for cyclic carbonate, mediated by guanidine and tetrabutylammonium iodide (TBAI) co-catalysts. The noncatalyt...
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Published in | New journal of chemistry Vol. 48; no. 2; pp. 920 - 932 |
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Main Authors | , , , |
Format | Journal Article |
Language | English |
Published |
02.01.2024
|
Online Access | Get full text |
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Summary: | Density functional theory (DFT) calculations at the M062X-D3/def2-TZVP//M062X-D3/def2-SVP level of theory were employed to reveal the mechanism of the reaction between CO
2
and styrene oxide for cyclic carbonate, mediated by guanidine and tetrabutylammonium iodide (TBAI) co-catalysts. The noncatalytic reaction occurred
via
a concerted mechanism, with energy barriers as high as 64.1 and 78.0 kcal mol
−1
. Three elementary steps were included in the catalytic reaction, and epoxide ring-opening by nucleophilic attack of an iodide anion was predicted to be the rate-determining step (RDS). Guanidine acted as the H-bond donor to activate styrene oxide by (N)H⋯O interaction, facilitating epoxide ring-opening with a low activation barrier (Δ
G
≠
= 22.2–29.6 kcal mol
−1
). A good linear correlation between the acidity of the NH group in the guanidine and the energy barrier in the epoxide ring-opening step was observed. The introduction of an amide group could strengthen the hydrogen bonding ability of the guanidine catalyst toward a styrene oxide substrate, decreasing the activation barrier for the cyclic carbonate product. When the guanidine–Cu(
i
) complex was used as the Lewis acid catalyst, the styrene oxide was activated by O⋯Cu(
i
) coordination in organometallic catalysis. The energy barriers in the presence of guanidine–Cu(
i
)/TBAI catalysts could be decreased in contrast to the non-catalytic reaction. |
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ISSN: | 1144-0546 1369-9261 |
DOI: | 10.1039/D3NJ04395A |