Carbonyldiimidazole
1,1'-Carbonyldiimidazole (CDI) is an organic compound with the molecular formula (C3H3N2)2CO. It is a white crystalline solid. It is often used for the coupling of amino acids for peptide synthesis and as a reagent in organic synthesis.
Preparation
CDI can be prepared straightforwardly by the reaction of phosgene with four equivalents of imidazole under anhydrous conditions. Removal of the side product, imidazolium chloride, and solvent results in the crystalline product in ~90% yield.
In this conversion, the imidazole serves both as the nucleophile and the base. An alternative precursor 1-(trimethylsilyl)imidazole requires more preparative effort with no corresponding advantages.
CDI hydrolyzes readily to give back imidazole:
The purity of CDI can be determined by the amount of CO2 that is formed upon hydrolysis, since the gas is formed on a 1:1 molar ratio.
Use in synthesis
CDI is mainly employed to convert alcohols and amines into carbamates, esters, and ureas.
Acid derivatives
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