The Chemistry of N–CO₂Bonds: Synthesis of Carbamic Acids and Their Derivatives, Isocyanates, and Ureas

The Carbon Dioxide Molecule and the Effects of Its Interaction with Electrophiles and Nucleophiles

“…Such structural modification is observed every time the electrophilic carbon atom of CO 2 is involved in an interaction with electron-rich species (amines, alcohols, carbanions, etc.). Upon interaction, the nucleophilicity of the O atoms of CO 2 increases favoring the interaction with electrophilic species [148][149][150].…”

Interaction of CO2 with Electron-Rich Moieties

“…In addition to the absorption at 1545 cm À1 , assigned to carbamate anion BnNHCO 2 À , the IR spectrum of an equilibrated solution also showed bands produced by free amine (3390 and 3320 cm À1 ) and free CO 2 [18]. A somewhat different behavior has been described for unsubstituted carbamic acid H 2 NCO 2 H [10,11]. The latter species has not yet been isolated as a pure compound, but it has been detected by several methods, including IR spectroscopy.…”

“…The reactivity of amines with CO 2 depends on the nature of the organic moiety they bear and the reaction conditions. In fact, under strictly anhydrous conditions, although tertiary aliphatic amines do not absorb CO 2 , aliphatic primary and secondary amines, as well as ammonia itself, react quickly with carbon dioxide to form the corresponding ammonium carbamates (3.8) which, in a few cases, have been fully characterized in the solid state by X-ray diffraction [10,11].…”

“…4), are potential carriers or sources of carbamic group and, if the transfer of "RR 0 NCO 2 " moiety to a suitable organic substrate is accomplished, can be used in the synthesis of organic carbamates, which are potential precursors of ureas and/or isocyanates [10]. To date, much effort has been made to develop new safe CO 2 -based synthetic methodologies for these classes of chemicals, usually obtained through hazardous phosgenation methods [46,47].…”

“…Nowadays, the chemistry of amines with CO 2 is drawing more and more attention, mainly because of its potential applications [10,11]. In addition to the traditional uses in chemical industry (Solvay process, synthesis of urea), new applications have begun to emerge.…”