Iridium-Catalyzed Annulative Coupling of 2-Arylbenzoyl Chlorides with Alkynes: Selective Formation of Phenanthrene Derivatives

Abstract

2-Arylbenzoyl chlorides undergo annulative coupling with internal alkynes in the presence of a catalyst system of [IrCl(cod)]2/P(t-Bu)3 to selectively afford the corresponding phenanthrene derivatives accompanied by elimination of carbon monoxide and hydrogen chloride. The reaction occurs without addition of any external base. Deuterium-labeling experiments using 2-(d5-phenyl)benzoyl chloride suggest that the rate-determining step does not involve the C2'-H bond cleavage. Formation of a [(t-Bu)3PH][(biphenyl-2,2'-diyl)Ir(CO)Cl2] complex dimer, of which the structure was determined by single-crystal X-ray analysis, from a stoichiometric reaction at 60 °C without addition of alkyne also supports the facile C-H cleavage.

Formation of 5-membered metallacycles at iPrPCPIr by C–H, O–H, and C–CO bond cleavage

“…These results indicate that the reaction of the iPr PCPIr fragment with biphenyl involves a double C-H activation with concomitant release of hydrogen (Scheme 3). While metallofluorene complexes of iridium are known, they have all been synthesized/ observed by reaction of 2,2 0 -dilithiobiphenyl with an iridium halide [35], by C-C activation of biphenylenes [30,36,37], or net C-CO and C-H activation of 2-arylbenzoyl chlorides [38]. To the best of our knowledge, the PCPIr system is the first example of iridium 2,2 0 -biphenyl complexes formed by double C-H activation, although double C-H activation of biphenyl with (dtbpm)Pt 0 is known [39].…”

Expedition to Phenanthrene Nucleus: A Two‐decade Research on Bench

“…Finally, the reductive elimination in both pathways affords product 15 (Scheme 37). [51] Fukushima and co-workers explored CÀ C bond coupling reaction using a borafluorene containing a BÀ Cl moiety (80) with alkynes 10 undergoes sequential 1,2-carboboration 81, followed by deborylation/Csp 2 -Csp 2 coupling reactions, leading to aromatic molecules 15. The first step affording a borepin derivative, proceeds efficiently between the borafluorene and various alkynes by simply mixing of these substrates.…”

Rhodium-Catalyzed Oxidative Annulation of (2-Arylphenyl)boronic Acids with Alkynes: Selective Synthesis of Phenanthrene Derivatives

“…It is noted that the yields of compounds 3ba and 3da were significantly improved compared with the previous method using the corresponding acid chlorides under iridium catalysis. 10 This annulation protocol was successfully expanded to the synthesis of 9,9′-biphenanthrenes using diynes as coupling partners (Equation 2). 9,13 Thus, 1,4-dialkylbuta-1,3diynes 4a and 4b underwent twofold cyclization to give 5aa and 5ab upon treatment of boronic acid 1a using a stoichiometric amount of the copper salt.…”