Synthese von 4-(sec-Amino)-1,3-oxazin-2-onen und 4-(sec-Amino)-1,3-oxazin-2-thionen über elektrocyclische Ringschlußreaktion

The title compounds3 and4 are easily obtainable by reaction of 2-acyl-1-chloro-enamines2 with trimethylsilyl-isocyanate, trimethylsilyl-isothiocyanate or sodium rhodanide, respectively. Primarily formed acylvinyl-iso(thio)cyanatesD, G spontaneously undergo electrocyclization. A one-pot operation leads directly to 4-amino-1,3-oxazine-2-thiones4 starting from acylketenedichlorides1 via2 by successive addition of secondary amine and sodium rhodanide. Reaction of2 with ammonium dithiocarbamate results in an unexpected formation of4. Treatment of4 with mercuric acetate offers a further access to 4-amino-1,3-oxazine-2-ones3. Finally,3 are obtained from2 on the sequence of ammonolysis to acylketeneaminals5 and phosgenation. Characteristic scopes and limitations as well as mechanistic features of these transformations are discussed.

Herrn Prof. Dr.Klaus Hafner zum 60. Geburtstag gewidmet.