2,2′-Biphenols via Protecting Group-Free Thermal or Microwave-Accelerated Suzuki–Miyaura Coupling in Water

Abstract

User-friendly protocols for the protecting group-free synthesis of 2,2'-biphenols via Suzuki-Miyaura coupling of o-halophenols and o-boronophenol are presented. The reactions proceed in water in the presence of simple additives such as K2CO3, KOH, KF, or TBAF and with commercially available Pd/C as precatalyst. Expensive or laboriously synthesized ligands or other additives are not required. In the case of bromophenols, efficient rate acceleration and short reaction times were accomplished by microwave irradiation.

Selective Synthesis of Partially Protected Nonsymmetric Biphenols by Reagent‐ and Metal‐Free Anodic Cross‐Coupling Reaction

“…[5,6] In particular, nonsymmetric 2,2'-biphenols have exceptional properties as building blocks for ligands in molecular catalysis, [7] bioactive materials, [3] and natural products. [8,9] Classically, nonsymmetric 2,2'-biphenols are prepared via transition-metal-catalyzed coupling reactions. [8,9] Classically, nonsymmetric 2,2'-biphenols are prepared via transition-metal-catalyzed coupling reactions.…”

“…[5] Accordingly, an efficient and selective route to these structural entities attracts considerable attention within the chemical community. [8,10] Following this strategy, the substrates are activated by introduction of specific leaving groups and this requires much effort and often harsh reaction conditions. [8,10] Following this strategy, the substrates are activated by introduction of specific leaving groups and this requires much effort and often harsh reaction conditions.…”

Eco-Friendly Physical Activation Methods for Suzuki–Miyaura Reactions

“…Schmidt et al [124] have investigated the protecting group-free synthesis of 2,2 -biphenols via heterogeneously catalyzed SMC under MW irradiation (see Scheme 55). Palladium on charcoal was adopted as the simple and conveniently available heterogeneous catalyst.…”

Pd/C Catalysis under Microwave Dielectric Heating

“…A protecting group free synthesis of biphenol aryl derivatives, 10, can be accomplished through a MW-assisted Pd/C-catalyzed Suzuki-Miyaura coupling in water starting from o-bromophenols, 8, and substituted boronophenols, 9 (Scheme 4) [21]. A careful evaluation on how the substituent position in 9 influenced the reaction efficiency was also reported: the m-boronophenol was the most reactive substrate, followed by the p-isomer.…”