Synthesis of 9,10‐Phenanthrenes via Rh(III)‐Catalyzed [4+2] Annulation of 2‐Biphenylboronic Acids with Diazo Compounds

Abstract

Comprehensive Summary A Rh(III)‐catalyzed, transmetalation triggered C—H activation/annulation of 2‐biphenylboronic acids with diazo compounds from β‐keto esters or 1,3‐dicarboxylates has been developed, leading to the synthesis of two kinds of 9,10‐phenanthrenes. Notably, a rhodacyle was synthesized by treating the rhodium catalyst with stoichiometric amounts of 2‐biphenylboronic acids and pyridine, which was further verified to be active for the catalytic system. The reactions proceeded under redox‐neutral and air‐tolerant conditions to produce a series of all‐carbon six‐membered rings with high efficiency.

Transition metal-catalyzed reactivity of carbenes with boronic acid derivatives for arylation (alkylation) and beyond

“…In 2023, Liu and Chang's group reported the Rh( iii )-catalyzed [4 + 2] annulation reaction to synthesize 9,10-phenanthrenes. 48 The reaction involves the initial transmetalation of [1,1′-biphenyl]-2-ylboronic acid 225 with the Rh( iii )-catalyst followed by C–H activation to form the Rh–carbene intermediate 230 with β-keto ester 226 . Then migratory insertion and subsequent cyclization followed by dehydration deliver the 9,10-phenanthrenes 227 (Scheme 30b).…”

“…In 2023, Liu and Chang's group reported the Rh(III)-catalyzed [4 + 2] annulation reaction to synthesize 9,10-phenanthrenes. 48 The reaction involves the initial transmetalation of The authors explored the substrate scope with electronically biased substrates (Scheme 30c). However, in some cases, mixtures of regioisomers were observed.…”

Application of Sulfoxonium Ylides or Iodonium Ylides in Rhodium‐Catalyzed Synthesis of Phenanthrenes

“…[14] Therefore, exploring new pathways on the synthesis of phenanthrene derivatives is of great significance for the development of optoelectronic active materials and the screening of bioactive molecules. Inspired by recent transmetalation triggered reactions of arylboronic acids [15] and combined with our previous works on transition-metal-catalyzed CÀ H bond activation and cyclization, [16] we herein seek to report a rhodiumcatalyzed transmetalation-initiated CÀ H bond activation and annulation of 2-biphenylboronic acids with sulfoxonium ylides or iodonium ylides leading to a series of substituted phenanthrene derivatives (Scheme 1c). This protocol possesses the following advantages: stable and easily available substrates, simple operation, redox-neutral conditions and one-step construction of phenanthrene derivatives containing three all carbon rings through ylides.…”