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Synfacts 2010(8): 0867-0867
DOI: 10.1055/s-0030-1257851
DOI: 10.1055/s-0030-1257851
Synthesis of Heterocycles
© Georg Thieme Verlag
Stuttgart ˙ New York
Copper-Catalyzed Synthesis of Pyridine N-Oxides from α,β-Unsaturated Oximes
I. Nakamura*, D. Zhang, M. Terada
Tohoku University, Sendai, Japan
Weitere Informationen
Publikationsverlauf
Publikationsdatum:
22. Juli 2010 (online)

Significance
Reported is the synthesis of highly substituted pyridine N-oxides 2 via the copper-catalyzed tandem [2,3]-rearrangement and 6π-3-azatriene electrocyclization of (E)-O-propargylic α,β-unsaturated oximes 1. Alkyl substituents on the oxime fragment were well tolerated. The presence of an electron-withdrawing group on the acetylene (R4 = 4-F3CC6H4) led to a moderate yield of 2, whilst the same group at the propargylic position (R³) led to decomposition of the starting materials. The E-geometry of the oxime is crucial to obtain the pyridine N-oxide, as the Z-stereoisomer leads to a dihydroisoxazole product via alkylidene group transfer.