Some reactions of enaminones with isothiocyanates

Abstract

Two primary and two secondary enaminones derived from cyclohexane-1,3-dione have been shown to react with methyl isothiocyanate and phenyl isothiocyanate. The dimedone derivatives (1) and (2) only reacted at high temperature to give products of C-2 substitution, (4)–(6). The primary enaminones (1) and (10) were deprotonated with strong bases to give products of N-substitution, (8), (9), (11), and (12). 3-Aminocyclohex-2-enone (10) reacted with methyl isothiocyanate in the presence of sodium hydride to give an unexpected new spirodihydrotriazine (15) the structure of which was established by an X-ray crystal structure determination of its diethyl acetal (16). The reaction of 5,5-dimethyl-3-methylaminocyclohex-2-enone (2) with sodium hydride and phenyl isothiocyanate in tetrahydrofuran gave the same mixture of four products as the reaction of 3-anilino-5,5-dimethylcyclohex-2-enone (3) with methyl isothiocyanate under the same conditions.