Cu-Catalyzed Skeletal Rearrangement of O-Propargylic Electron-Rich Arylaldoximes into Amidodienes

Abstract

O-Propargylic oximes that possess an electron-rich p-(dimethylamino)phenyl group at the oxime moiety and an alkyl group at the propargylic position were efficiently converted in the presence of Cu(I) catalysts to the corresponding 1-amidodienes in good to excellent yields. The reaction proceeded via a 2,3-rearrangement, followed by isomerization of the resulting N-allenylnitrone to the amide, presumably through the oxaziridine intermediate.

Copper‐Catalyzed Skeletal Rearrangement of O‐Propargyl Oximes: A Mechanistic Manifold

“… Different compounds reported by Nakamura et al . from the Cu‐catalyzed rearrangement of O ‐propargyl oximes.…”

“…reported on the skeletal rearrangement of different O ‐propargyl aldoximes catalyzed by Cu. They changed only certain reaction parameters and modified the substituents of this organic skeleton and obtained a variety of N‐containing cyclic and acyclic compounds and thus furnished this chemistry with strong versatility . Notably, they found a dependence between the electronic nature of the aryl group at the oxime moiety (R 3 in Figure ) and the product obtained in the Cu‐mediated rearrangement of O ‐propargyl arylaldoximes.…”

“…If R 3 is an electron‐poor aromatic group, four‐membered cyclic nitrones 4 (azete oxides) are produced. However, if R 3 is an electron‐rich aryl group, the resulting products are 1‐amidodienes 12 (Figure ) . Moreover, the inclusion of an olefin moiety at R 3 instead of an aryl group changes the outcome of this reaction dramatically to furnish 2,3,(4),(5)‐multisubstituted pyridine N ‐oxides 19 (Figure ) …”

“…Although Nakamura et al . performed a thorough synthetic study to transform a series of O ‐propargyl oximes into several different substrates in an efficient one‐pot fashion, the mechanism that these rearrangement reactions follow is still not clear.…”

Copper-Catalyzed Skeletal Rearrangements ofO-Propargylic Oximes via Cleavage of a Carbon-Oxygen Bond

“…In this account, we present our recent developments in the copper‐catalyzed intramolecular transformations of O ‐propargylic oximes via cleavage of the carbon–oxygen bond, leading to four‐membered cyclic nitrones (azete oxides),[] pyridine N ‐oxides,[] and amidodienes (Scheme ). [] However, before we present the experimental results of these reactions, we would first like to share the events leading up to our fortuitous encounter with the beautiful molecule.…”