Efficient Synthesis of Oxygenated Terphenyls and Other Oligomers: Sequential Arylation Reactions Through Phenol Oxidation–Rearomatization

Abstract

One by one: starting from simple phenols, a diverse series of oxygenated terphenyl compounds can be prepared in a concise and practical manner using sequential arylation reactions involving phenol oxidation/rearomatization and quinone monoacetal intermediates. Many of the terphenyl products can be used for preparing well-defined oligomers and, furthermore, contain valuable functional groups that can be transformed for further diversification.

Photocatalytic Phenol–Arene C–C and C–O Cross‐Dehydrogenative Coupling

“…1‐Hydroxy‐4‐methoxy‐2‐(2,4,5‐trimethoxyphenyl)naphthalene (2ab): [17b] 1 H NMR (300 MHz, CDCl 3 ): δ = 8.39–8.32 (m, 1 H), 8.26–8.19 (m, 1 H), 7.59–7.47 (m, 2 H), 6.97 (s, 1 H), 6.73 (s, 1 H), 6.72 (s, 1 H), 6.70 (s, 1 H), 4.00 (s, 3 H), 3.97 (s, 3 H), 3.90 (s, 3 H), 3.86 (s, 3 H) ppm. 13 C NMR (75 MHz, CDCl 3 ): δ = 149.64, 149.59, 149.45, 144.56, 142.82, 126.53, 126.04, 125.88, 125.67, 122.75, 121.52, 119.53, 117.97, 115.37, 106.42, 98.96, 57.87, 56.61, 56.20, 55.82 ppm.…”

“…3‐( tert ‐Butyl)‐2‐hydroxy‐2′,4′,5,5′‐tetramethoxybiphenyl (4ab): [17d] R f = 0.33 (hexane/EtOAc, 3:1). 1 H NMR (300 MHz, CDCl 3 ): δ = 6.93 (d, J = 3.1 Hz, 1 H), 6.86 (s, 1 H), 6.67–6.64 (m, 2 H), 6.09 (s, 1 H), 3.95 (s, 3 H), 3.87 (s, 3 H), 3.83 (s, 3 H), 3.80 (s, 3 H), 1.45 (s, 9 H) ppm.…”

“…Recent developments in the field of oxidative phenol–arene C–C cross‐coupling have demonstrated the applicability of hypervalent iodine‐based oxidants, as reported by Kita and co‐workers, electrochemical methods, as described by Waldvogel and co‐workers, and iron‐catalyzed transformations by using t BuOO t Bu as terminal oxidant, published by Pappo and co‐workers . These strategies provided a selective and easy access to the respective cross‐coupling products, but are typically limited in terms of efficiency and (chemo)selectivity to highly fluorinated solvent systems, in particular, 1,1,1,3,3,3‐hexafluoro‐2‐propanol (HFIP), which are expensive and have a large environmental footprint.…”

Recent Developments in Transition Metal‐Free Cross‐Dehydrogenative Coupling Reactions for C–C Bond Formation

“…Dohi et al reported a sequential arylation method which involved oxidation followed by subsequent rearomatization of phenols to give oxygenated terphenyls along with a series of more elongated oligomers via quinone monoacetals as key intermediates (Scheme 63). [ 51 ] The reaction occurred in the presence of PIDA as an oxidant in methanol and montmorillonite (MT) clay as a solid acid promoter to form the aryl–aryl bond. The aryl quinone monoacetal obtained by the coupling of phenol with 1,3‐dimethoxy benzene was subjected to a variety of oxygenated aromatic nucleophiles and the corresponding oxygenated terphenyls were obtained in good to excellent yields.…”

Molecular Complexity from Aromatics: Recent Advances in the Chemistry of paraQuinol and Masked para‐Quinone Monoketal

“…[39] This method of dearomatization has been extensively utilized in the development of methodologies and organic synthesis (Scheme 7). [40]…”