The First Example of Isomeric Solid Amide and Its Enol

The first example of a crystalline amide and its tautomeric enol was obtained for the amide MeNHCSCH(CN)CONHMe (8) and its enol MeNHCSC(CN)C(OH)NHMe (9). Their X-ray structures were determined, and their structural features resemble those of other related amides and enols.
No other example of a similar pair was obtained. In solution, both 8 and 9 and a small percentage of the isomeric enol of thioamide MeNHCOC(CN)C(SH)NHMe (10) were obtained in solvent-dependent compositions, which are rapidly established.