A carbon dioxide-promoted three-component Strecker reaction†
A three-component Strecker reaction of aldehydes, amines and KCN has been performed for the first time in supercritical carbon dioxide. In the proposed procedure, non-toxic and non-flammable carbon dioxide acts not only as an environmentally benign reaction medium but also as a reaction promoter via in situ formation of carbonic acid which provides a gradual release of the true cyanating agent (HCN) from available KCN. The reaction conditions (pressure, temperature, and concentrations of reagents) were optimized, and various aromatic and aliphatic amines and aldehydes were transformed into valuable α-amino nitriles including prospective pharmacological substances. The equimolar amount of used cyanogen reagent, carrying out the process in a sealed autoclave in a ‘green’ solvent medium under mild conditions (90 bar, 35 °C) along with the high yields of products and the scalability of the developed procedure make it suitable for sustainable industrial applications.