Stereoselective Metal-Free Reaction of Imidazoles with Isothiocyanates Involving Cyanophenylacetylene: A Shortcut to N-(Z-Alkenyl)imidazole-2-carbothioamides
摘要:
N-(Z)-(2-Cyano-1-phenylethenyl)imidazole-2-carbothioamides have been synthesized in up to 91% yield by the new reaction between 1-substituted imidazoles and isothiocyanates in the presence of cyanophenylacetylene under catalyst-and solvent-free conditions at room temperature. The reaction proceeds via zwitterion-carbene intermediates which are trapped by isothiocyanates to form the zwitterion with ambident N-S anionic site, which then undergoes stereo- and regioselective migration of the alkenyl moiety.