Rhodium(III)‐Catalyzed Cascade Redox‐Neutral C–H Functionalization and Aromatization: Synthesis of Unsymmetrical ortho‐Biphenols

Abstract

An efficient rhodium(III)-catalyzed coupling reactiono fN-aryloxyacetamides with 6-diazo-2-cyclohexenones throughacascade redox-neutral C-H functionalization and aromatization hasb een developed. This novela nd scalable transformation provides as traightforward wayt oc onstruct unsymmetrical ortho-biphenols with broad substrate scope under mild and redox-neutral conditions.T he synthetic utility of this approach is demonstrated in the late-stage functionalization of bioactive compounds and the synthesis of an optically active ortho-biphenol.

Transition-Metal-Catalyzed Cross-Couplings through Carbene Migratory Insertion

“…Very recently, Liu and co-workers employed 6-diazo-2-cyclohexenones as carbene precursors to react with N-phenoxyacetamides, which provided an efficient method for the synthesis of unsymmetrical ortho-biphenols. 353 Except for a spontaneous aromatization process, the reaction mechanism is similar to that of Wang's work depicted in Scheme 109a (Scheme 109b).…”

Modular bismacycles for the selective C–H arylation of phenols and naphthols

“…The preference of Bi(V) for arylation of estrone at the 4-position is apparently unique in the literature, and provides a direct complement to metal-catalyzed directed C-H arylations which favor functionalization of the 2-position. 17,71,72,73,74 Both 2-and 4-arylated estrones exhibit biological activity, 75 so the ability to access both regioisomers in a single operation is of potential utility in discovery projects.…”

Preparation and Synthetic Applications of Five-to-Seven-Membered Cyclic α-Diazo Monocarbonyl Compounds

“…To get to a chiral biphenol, an L-(−)-carvone diazo derivative is used, as described above. The resulting product with N -β-naphthoxyacetamide is obtained in a low yield but with excellent enantiopurity ( Scheme 63 ) [ 97 ].…”

“…Apparently, the substituent in position 5 of the starting diazo compound would be oriented towards the sterically encumbered pentamethyl cyclopentadienyl ligand, which explains the low yield obtained with 6-diazo-5-methylcyclohex-2-enone and the L-(−)-carvone derivative. At the same time, using β-naphthoxyacetamide gives a rather high product yield ( Scheme 64 ) [ 97 ].…”