Isocyanates, Part 4. Convenient Phosgene-Free Method for the Synthesis and Derivatization of Enantiopure α-Isocyanato Carboxylic Acid Esters
31. Dezember 2000 (online)
A novel phosgene-free procedure for the synthesis of α-isocyanato carboxylic acid esters starting from α-amino acid esters has been achieved. The isocyanates are obtained enantiomerically pure (>99% ee) by a DMAP-catalyzed isocyanation with di-tert-butyl dicarbonate, which proceeds in 10 min at room temperature. In situ derivatization of the isocyanates by reaction with amines and alcohols affords the corresponding enantiopure ureas and carbamates.
di-tert-butyl dicarbonate - 4-dimethylaminopyridine - α-amino acid esters - α-isocyanato carboxylic acid esters - β-carboline derivatives