Synthesis of non-C2 symmetrical NOBIN-type biaryls through a cascade N-arylation and [3,3]-sigmatropic rearrangement from O-arylhydroxylamines and diaryliodonium salts

Nondirected Ortho C-H Arylation for One-Pot Synthesis of Biaryl Scaffolds via In Situ Generated Mixed Acetal

Herein, we introduce a mild and efficient method for synthesizing aniline biaryls and unsymmetrical phenol biaryls through iodine-catalyzed coupling of quinone imine ketals (QIKs)/quinonemonoacetals (QMAs) and β-naphthols. This approach allows for the unusual formation of ortho-substituted anilines and phenols, valuable in pharmaceuticals and advanced materials but typically difficult to produce. Our method achieves high ortho-selectivity without needing transition metals or external/internal templates. The process involves a [3,3] sigmatropic rearrangement of the in situ generated mixed acetal, which is the key intermediate. Notable features include scalability, broad functional group tolerance, and late-stage derivatization of natural products using a cost-effective, air-tolerant catalytic system, eliminating the need for hazardous catalysts.

Copper-catalyzed [1,3]-nitrogen rearrangement of O-aryl ketoximes via oxidative addition of N–O bond in inverse electron flow†

The [1,3]-nitrogen rearrangement reactions of O-aryl ketoximes were promoted by N-heterocyclic carbene (NHC)-copper catalysts and BF₃·OEt₂ as an additive, affording ortho-aminophenol derivatives in good yields. The reaction of substrates with electron-withdrawing substituents on the phenol moiety are accelerated by adding silver salt and modifying the substituent at the nitrogen atom. Density functional theory calculations suggest that the rate-determining step of this reaction is the oxidative addition of the N–O bond of the substrate to the copper catalyst. The negative ρ values of the substituent at both the oxime carbon and phenoxy group indicate that the donation of electrons by the oxygen and nitrogen atoms accelerates the oxidative addition.

[1,3]-Nitrogen rearrangement reactions of O-aryl ketoximes was catalytically promoted by IPrCuBr and BF₃·OEt₂. The oxidative addition of the N–O bond to the Cu catalyst is accelerated by donation of electrons from both nitrogen and oxygen atoms.

Diaryliodonium(III) Salts in One-Pot Double Functionalization of C–IIII and ortho C–H Bonds

Since the 1950s, diaryliodonium(III) salts have been demonstrated to participate in various arylation reactions, forming aryl–heteroatom and aryl–carbon bonds. Incorporating the arylation step into sequential transformations would provide access to...