Spontaneous α-C-H Carboxylation of Ketones by Gaseous CO2 at the Air-water Interface of Aqueous Microdroplets

Pallab Basuri; Sinchan Mukhopadhyay; K S S V Prasad Reddy; Keerthana Unni; B K Spoorthi; Jenifer Shantha Kumar; Sharma S R K C Yamijala; Thalappil Pradeep

doi:10.1002/anie.202403229

Spontaneous α-C-H Carboxylation of Ketones by Gaseous CO2 at the Air-water Interface of Aqueous Microdroplets

Angew Chem Int Ed Engl. 2024 Apr 5:e202403229. doi: 10.1002/anie.202403229. Online ahead of print.

Authors

Pallab Basuri¹, Sinchan Mukhopadhyay¹, K S S V Prasad Reddy¹, Keerthana Unni¹, B K Spoorthi¹, Jenifer Shantha Kumar¹, Sharma S R K C Yamijala¹, Thalappil Pradeep²

Affiliations

¹ Indian Institute of Technology Madras, Department of Chemistry, INDIA.
² Indian Institute of Technology, Department of Chemistry, Madras, 600036, Madras, INDIA.

PMID: 38577991
DOI: 10.1002/anie.202403229

Abstract

We present a catalyst-free route for the reduction of carbon dioxide integrated with the formation of a carbon-carbon bond at the air/water interface of negatively charged aqueous microdroplets, at ambient temperature. The reactions proceed through carbanion generation at the α-carbon of a ketone followed by nucleophilic addition to CO2. Online mass spectrometry reveals that the product is an α-ketoacid. Several factors, such as the concentration of the reagents, pressure of CO2 gas, and distance traveled by the droplets, control the kinetics of the reaction. Theoretical calculations suggest that water in the microdroplets facilitates this unusual chemistry. Furthermore, such a microdroplet strategy has been extended to seven different ketones. This work demonstrates a green pathway for the reduction of CO2 to useful carboxylated organic products.

Keywords: Carbon dioxide reduction; Mass spectrometry; air-water interface; carbanion; microdroplet chemistry.