karbodiimin

Karbodiimins are a class of organic compounds characterized by the functional group R-N=C=N-R', where R and R' are organic substituents. The central carbon atom is double-bonded to two nitrogen atoms, forming a cumulene system. This unique structure imparts significant reactivity to karbodiimins, making them valuable reagents in organic synthesis.

The most prominent application of karbodiimins is as coupling agents, particularly in the formation of amide bonds. They facilitate the reaction between a carboxylic acid and an amine, activating the carboxylic acid by forming an O-acylisourea intermediate. This intermediate is highly reactive towards nucleophilic attack by the amine, leading to the formation of the desired amide and a substituted urea byproduct. This method is widely used in peptide synthesis and the creation of other amide-containing molecules.

Beyond amide coupling, karbodiimins are employed in esterification reactions, dehydration processes, and the synthesis of heterocycles. Their ability to remove water molecules indirectly makes them effective dehydrating agents. The reactivity of karbodiimins can be influenced by the nature of the R and R' groups, allowing for fine-tuning of their properties for specific synthetic needs. Common examples include dicyclohexylcarbodiimide (DCC) and diisopropylcarbodiimide (DIC), which differ in their solubility and handling characteristics.