Imidazoline-4-thiones from cyanothioformamides and aldehyde imines: Formation, aromatization, and acetylation

The reaction of N-methyl- (3a) or N-phenylcyanothioformamide (3b) with acetaldimine (5a, as 1-amino-1-ethanol) gives 5-(amino)imidazolidine-4-thiones 6B. Product 6a reacts with a second equivalent of 3a to give 8 which in turn is oxidized to disulfide 9. Using araldimines 5b,c, only 1:2 intermediates 10 derived from 3a, b and two moles of the imine 5 are formed, but proved to be easily oxidized to disulfides 11. Acetylation of 6 occurs chemoselectively on the exocyclic nitrogen and finally also on the thione sulfur to give 14 via 13.