Copper-mediated synthesis of N-alkenyl-α,β-unsaturated nitrones and their conversion to tri- and tetrasubstituted pyridines

Abstract

SummaryA Chan–Lam reaction has been used to prepare N-alkenyl-α,β-unsaturated nitrones, which undergo a subsequent thermal rearrangement to the corresponding tri- and tetrasubstituted pyridines. The optimization and scope of these transformations is discussed. Initial mechanistic experiments suggest a reaction pathway involving oxygen transfer followed by cyclization.

Diastereoselective Synthesis of Nine‐Membered Heterocycles via the Cycloaddition and Sequential Rearrangement of N‐Vinyl Nitrones with Isocyanates

“…However, using cyclic N ‐vinyl nitrones failed to afford the desired products at 60 °C, resulting in only decomposition of the starting materials. Lowering the temperature allowed the successful reaction of cyclic N ‐vinyl nitrones ( 1 r – t ), which afforded the desired products 3 r – t in good yields, incorporating six‐ and seven‐membered rings accompanied by some pyridine byproducts also reported by Anderson's group . Interestingly, compound 3 s was obtained in 59% yield as only one isomer, even though a phenyl group was present on the six‐membered ring.…”

Recent Advances in the Arylation and Alkenylation of N–O Bonds

“…Good yields were achieved, and the Eisomers were obtained as the major products (Scheme 62). 48 The reaction proceeded smoothly for electron-donating-and electron-withdrawing-substituted α,β-unsaturated oximes, as well as heteroarene-substituted α,β-unsaturated oximes. Interestingly, when cyclooctadiene was added to the reaction mixture, the amount of copper acetate could be reduced to 10 mol%.…”

Synthesis and Transformations of Nitrones for Organic Synthesis

“…N-Vinylnitrones have been prepared from fluorenone oxime by the Cu(OAc) 2 -mediated reactions with alkenylboronic acids (eq 25). 98,99 Similarly, Cu(OAc) 2promoted reactions of malonate-derived oximes with vinylboronic acids give N-alkenylnitrones, which undergo 4πelectrocyclization to form azetidine nitrones (Scheme 5). 100 Copper-catalyzed reaction of oximes with cyclopropenes using chiral phosphines gives chiral N-cyclopropylnitrones (eq 26).…”