Mn- and Co-Catalyzed Aminocyclizations of Unsaturated Hydrazones Providing a Broad Range of Functionalized Pyrazolines

Manganese- and cobalt-catalyzed
aminocyclization reactions of unsaturated
hydrazones are reported. Whereas manganese catalysis provides access
to pyrazoline and tetrahydropyridazine alcohols, cobalt catalysis
for the first time paves the way for the selective formation of pyrazoline
aldehydes. Furthermore, various functional groups including hydroperoxide,
thiol derivatives, iodide, and bicyclopentane may be introduced via
manganese-catalyzed ring-forming aminofunctionalization. A progesterone
receptor antagonist was prepared using the aminocyclization protocol.