Substrate-controlled Rh(iii)-catalyzed regiodivergent annulation towards fused and spiro benzimidazoles. Issue 34 (16th August 2022)

• Record Type: Journal Article
• Authors: Huang, Ying-Ti; Barve, Indrajeet J.; Huang, Yi-Ting; Dhole, Sandip; Chiu, Wei-Jung; Sun, Chung-Ming
• Is Part Of: Organic & biomolecular chemistry. Volume 20:Issue 34(2022)
• Page Start: 6854
• Page End: 6862
• Publication Date: 2022-08-16
• Subjects: Chemistry, Organic -- Periodicals; Bioorganic chemistry -- Periodicals; Chemistry, Physical organic -- Periodicals; 547
• DOI: 10.1039/d2ob00906d
• Languages: English
• ISSNs: 1477-0520

Abstract

Abstract : Switchable selectivity towards the formation of two distinct products, benzimidazole-fused isoquinolines and benzimidazole-spiro isoindoles, can be achieved using unsubstituted and substituted benzimidazoles at the ortho -position of the phenyl ring. Abstract : A Rh(iii )-catalyzed cascade C–H activation and cyclization of 2-aryl benzimidazoles with maleimides for the synthesis of benzimidazole-fused isoquinolines and benzimidazole-spiro isoindoles is reported. Switchable selectivity towards the formation of these two distinct products can be achieved using unsubstituted and substituted benzimidazoles at the ortho -position of the phenyl ring. Mechanistically, C–H activation followed by migratory insertion of maleimide forms a Heck-type intermediate. Unsubstituted benzimidazole undergoes aza-Michael addition to form a (4 + 2) fused product, whereas ortho -substituted phenyl benzimidazole causes steric clash to deliver a (4 + 1) spiro-adduct favorably via acid-catalyzed intramolecular annulation.