Iron‐Catalyzed, Iminyl Radical‐Triggered Cascade 1,5‐Hydrogen Atom Transfer/(5+2) or (5+1) Annulation: Oxime as a Five‐Atom Assembling Unit

Abstract

By integration of iminyl radical-triggered 1,5-hydrogen atom transfer and (5+ +2) or (5+ +1) annulation processes, aseries of structurally novel and interesting azepine and spirotetrahydropyridine derivatives have been successfully prepared in moderate to good yields.T his method utilizes FeCl 2 as the catalyst and readily available oximes as five-atom units,w hile showcasing broad substrate scope and good functional group compatibility.The annulation products can be easily converted into many valuable compounds.M oreover,D FT calculation studies are performed to providesome insights into the possible reaction mechanisms for the (5+ +2) and (5+ +1) annulations.

Iron‐Catalyzed Radical Relay Enabling the Modular Synthesis of Fused Pyridines from Alkyne‐Tethered Oximes and Alkenes

“…The N−O bond of the oxime can be cleaved to generate an iminyl radical, followed by the 1,5‐HAT to form a γ‐carbon radical that would take part in C−C and carbon–heteroatom bond formations [9] . More recently, our group realized an iminyl radical‐triggered cascade 1,5‐HAT/(5+2) or (5+1) annulation protocol, in which the oximes served as five‐atom units [10] . Based on the aforementioned work, we rationally designed a new class of oximes bearing an alkyne moiety.…”

Iron‐Catalyzed Radical Relay Enabling the Modular Synthesis of Fused Pyridines from Alkyne‐Tethered Oximes and Alkenes

“…[9] More recently,o ur group realized an iminyl radical-triggered cascade 1,5-HAT/(5 + 2) or (5 + 1) annulation protocol, in which the oximes served as five-atom units. [10] Based on the aforementioned work, we rationally designed an ew class of oximes bearing an alkyne moiety.W eenvisioned that avinyl radical would be formed by an intramolecular 5-exo-dig addition. Such aradical species might be intercepted with the alkenes to give rise to the fused pyridines (Scheme 2a).…”

Iron‐Catalyzed, Iminyl Radical‐Triggered Cascade 1,5‐Hydrogen Atom Transfer/(5+2) or (5+1) Annulation: Oxime as a Five‐Atom Assembling Unit

“…Thestructure of 3a was unambiguously confirmed by single-crystal X-ray diffraction. [22] Thereaction afforded 3a in 33 %yield with 1,4dioxane as the solvent (entry 8), while showed significantly lower yields in MeCN,toluene,and DMSO (entries 9-11). A further improvement was achieved by using 1equiv of sodium pivalate as an additive (82 %, entry 14).…”

“…19386 www.angewandte.de (3aw), trifluoromethyl (3ax), fluoro (3ay), bromo (3ay), and chloro groups (3az), [23] were amenable to the reaction, affording the corresponding products in moderate yields.I n addition, the reactions between N-(2,4,6-trichlorophenyl)ma-leimide and various oximes can also generate the desired products (3aaa-3aae). Besides N-aryl maleimides,N -Me maleimide (3aaf)and NH-maleimide (3aag)can take part in the reactions to deliver the target products in synthetically useful yields.…”