No abstract

No abstract

No abstract

The recently described reaction between lithium hydride and addition products of acyl isothiocyanates with amines, methanol, and methanethiol in DMF followed by alkylation with methyl iodide is shown not to generate a new class of heterocycles -2,2,4-trisubstituted 2H-3,3-oxazetes but to yield N-acyl isothioureas, N-acyl mono-, and -dithioisocarbamates, respectively. The structures are confirmed by IR, mass, 'H-NMR, and 13C-NMR spectra. 2,2,4-Trisubstituierte ZH-l,3-Oxazete -Ein neuer Typ von Heterocyclen -Eine KlarstellungEs wird gezeigt, dal3 die kiirzlich beschriebene Reaktion von Lithiumhydrid mit Additionsprodukten aus Acylisothiocyanaten und Aminen, Methanol, sowie Methanthiol in DMF und nachfolgende Methylierung nicht zu neuen Heterocyclenden 2,2,4-trisubstituierten 2H-1,3-Oxazetenfiihrt, sondern N-Acylisothioharnstoffe, N-Acylmono-und -dithioisocarbamate ergibt. Deren Strukturen werden durch IR-, Massen-, 'H-NMR-und l3C-NMR-Spektren bestatigt.Recently Kristian, Kurschy, and Dzurillal) reported the synthesis of 2,2,4-trisubstituted 2H-1,3-oxazetes 1 -a hitherto undescribed class of four-membered heterocycles from acyl isothiocyanates via N-acyl thioureas, 0-methyl thiocarbamates, and methyl dithiocarbamates, respectively (Scheme 1).

The 13C NMR shifts of the E/Z mixtures of twelve, mainly ortho substituted, methyl N-methylthiob e d d a t e s have been completely assigned. The angles of twist about the aryl-imino-carbon bond were determined by means of the C-1 aryl shifts. Depending on the bulk of the ortho substituents the values vary from 18" in methyl 2-fluoro-N-methylthiobenzimidate (2) to 73" in methyl 4-bromo-N,2,6-trimethylthiob e d d a t e (E). An explanation for the 13C-E/Z-N-alkyl and -Salkyl resonances is facilitated by a new model which is initially based on the influence of electric fields.As this model is derived from amides, thioamides etc. it is possible to interpret the 13C-E/Z shifts in all related classes of compounds. The role of steric compression does not seem to be as important as was previously assumed.