[2, 3‐Bis‐(2‐pyridyl) pyrazine] as an Efficient Organocatalyst for the Direct C(sp2)‐H Arylation of Unactivated Arenes/Heteroarenes via C−H Bond Activation. Issue 38 (13th October 2020)

• Record Type: Journal Article
• Authors: Tiwari, Mohit K.; Yadav, Lalit; Chaudhary, Sandeep
• Is Part Of: ChemistrySelect. Volume 5:Issue 38(2020)
• Page Start: 11968
• Page End: 11975
• Publication Date: 2020-10-13
• Subjects: Organocatalyst -- Cross-coupling -- Direct arylation -- C−H bond activation -- SET mechanism; Chemistry -- Periodicals; 540.5
• DOI: 10.1002/slct.202003140
• Languages: English
• ISSNs: 2365-6549

Abstract

Abstract: Herein, we report the identification of 2, 3‐bis‐(2‐pyridyl) pyrazine as a new organocatalyst, which has been utilized for the direct cross‐coupling reactions of an aryl halide with unactivated arenes/heteroarenes via C(sp 2 ) ‐H bond activation. This transition metal‐free C−H arylation of unactivated benzenes with aryl halides (Ar−X; X=I, Br, Cl) underwent smoothly with only 10 mol% of an organocatalyst and in the presence of 3 equivalent of potassium tert ‐butoxide base which furnished a library of biaryls (3 a –u ) in up to 98 % excellent yield under milder reaction conditions. The mechanistic pathway involves the in‐situ formation of aryl radical anion intermediate and progressed via a single electron transfer (SET) mechanism. The wide substrate scope, high functional group forbearance, control/competition experiments, gram‐scale synthesis and kinetic studies signify the prominence and useful nature of the protocol along with the steadiness of the novel organocatalyst. Abstract : A new organocatalyst [2, 3‐bis‐(2‐pyridyl)pyrazine] has been identified for the direct C(sp 2 ) ‐H arylations of an aryl halides with unactivated arenes/heteroarenes via C(sp 2 ) ‐H bond activation is reported. This protocol is operationally simple and showed a broad range of functional group tolerance and substrate affinity. The wide substrate scope, high functional group tolerance, control/competition experiments, gram‐scale synthesis and kinetic studies further exemplify the importance and versatile nature of novel organocatalyst in this direct C(sp 2 ) ‐H arylations methodology.