Observation of guanidine-carbon dioxide complexation in solution and its role in 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 catalytic activity of these amines/guanidines in 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.