Synthesis of Pyridine and Isoquinoline Derivatives by the Palladium-Catalyzed Cyclization of Olefinic Ketone O-Pentafluorobenzoyloximes

Abstract

Pyridines and isoquinolines are synthesized from olefinic ketone O-pentafluorobenzoyloximes by treatment with a catalytic amount of Pd(PPh3)4 in the presence of (n-Bu)4NCl and triethylamine.

Palladium(0)-catalyzed synthesis of pyridines from β-acetoxy-γ,δ-unsaturated ketone oximes

“…In the presence of tetrabutylammonium chloride, the reaction became slower, and pyridine 3 was dominant instead of pyrrole 2. 10 The formation of pyridine via a 6-endo type cyclization was clearly due to the introduction of a methoxy group at the β-position, because the corresponding oxime lacking a β-methoxy substituent gave pyrrole exclusively under either reaction conditions. Generally, in the intramolecular Mizoroki-Heck reactions, 5-exo cyclization proceeded preferentially and the 6-endo cyclization products are rarely obtained.…”

Synthesis of Secondary Unsaturated Lactams via an Aza-Heck Reaction

“…With only a few exceptions, 16d, 25 all prior examples of aza-Heck reactions have been limited to the formation of simple or fused 5-membered rings. It is thus particularly notable that the bridged bicycle 17 can be readily prepared using this chemistry.…”

Electrocyclization‐Mediated Approach to 2‐Methyltriclisine, an Unnatural Analog of the Azafluoranthene Alkaloid Triclisine

“…One of them included the established thermal electrocyclization of an ortho-propenyl oxime, [24] while the second possibility consisted in the palladium-catalyzed cyclization of an oxime derived from the the 1-allylfluorenone derivative 17, as described by Tsutsui and Narasaka. [25] The latter transformation does not seem to imply isomerization of the allyl moiety and electrocyclization of the resulting intermediate; however, since its reported yields were only moderate, the first alternative was pursued.…”