3,3-Difluorocyclopropenes as Synthons for Substituted Pyridazines

The scalable preparative methodology for the synthesis of hardly accessible substituted 5-fluoropyridazines with a large variety of substituents was elaborated through the base-catalyzed [3+2] -cycloaddition of 3,3-difluorocyclopropenes with substituted diazomethanes. The reaction has shown broad scope and high regioselectivity. The fluorine atom in position 5 shows excellent reactivity and can be easily modified by another nucleophile. The mechanistic aspects of the reaction are proposed, discussed and confirmed by the DFT calculations