(252f) Reversible Reactions of CO2 with Amines Employing A Protection / Deprotection Mechanism

The reversible reaction of amines with carbon dioxide forming alkyl-ammonium carbamates is proposed as a new method for amine protection. The powerful neucleophilic properties of amines due to the electron pair on their nitrogen atoms often require the use of a protecting group during bi-functional coupling reactions. The deprotection mechanisms are very energy intensive, costly, or require the use of dangerous/ harsh chemicals. Our approach incorporates a single reversible reaction that utilizes a relatively safe and cheap protecting group, carbon dioxide. In this work, N-alkyl Benzophenone amines and N-alkyl Benzophenone Imines were synthesized using propylamine and propylamine-CO₂ carbamates. These carbamate structures serve as a potential switch in both the physical and chemical properties of the propylamine, as well as and altering the polarity and ionic characteristics of our reaction due to the resulting charged carbamate species upon reaction with CO₂. The propylamine-CO₂ carbamates showed a significant reduction in the product yield compared to unprotected propylamine along with an increase in its product yield once deprotection had occurred. The reactions were monitored and characterized by GC, ATR-FTIR and H¹NMR.