Observation of guanidine-carbon dioxide complexation in solution and its role in the reaction of carbon dioxide and propargylamines

The first observation of guanidine-CO2 'activation' complexes in solution using ATR-FTIR is reported. While cyclic guanidines TBD and MTBD form stable and detectable complexes with CO2, other guanidines and tertiary amines do not. Correlation with the catalytic activity of these amines/guanidines in the reaction between CO2 and propargylamines indicated that the basicity of the catalyst, rather than its ability to form complexes with CO2, is the origin of catalytic activity.