Unexpected Formation of 4-aryl-1-(Propane-2-ylidenehydrazono)-2,3-diazaspiro[5.5]undec-3-ene by the Reaction of Pyridazinethiones Derivatives with Hydrazine

Abstract

After making a new series of spiro[cycloalkane]pyridazinones with high Fsp3 character available, the new target was to synthesize derivatives comprising nitrogen-containing heterocycles, such as triazolo or tetrazolo rings. The corresponding thioxo derivatives (1a,b) seemed to be good starting materials for the synthesis of tetrazolo derivatives. The reaction of the pyridazinethiones (1a,b) with hydrazine surprisingly resulted in Schiff bases (3a,b) deriving from the reaction of hydrazones (2a,b) with acetone.