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

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. [ABSTRACT FROM AUTHOR]