Facile Synthesis of New Spirothiadiazolopyridazines by 1,3‐Dipolar Cycloaddition

Abstract

Abstract New derivatives of the spiro type of pyridazines have been synthesized by 1,3‐dipolar cycloaddition of N‐aryl‐C‐ethoxycarbonylnitrile imines with pyridazin‐3(2H)‐thiones. When the nitrile oxide was used, the corresponding pyridazin‐3(2H)‐one was obtained from the intermediate spirooxathiazole by elimination of isothiocyanate group. The peri‐ and regioselectivity of the reaction were ascertained by X‐ray analysis and 13C NMR spectroscopy of the cycloadducts 3–9. Keywords: Cycloadditionspyridazin‐3(2H)‐thioneregioselectivityspiro compoundsX‐ray analysis