title: H2O2/DMSO-Promoted Regioselective Synthesis of 3,3'-Bisimidazopyridinylmethanes via Intermolecular Oxidative C(sp(2))-H Bond Activation of Imidazoheterocycles.
abstract: In the past decade, metal-free approaches for C-C bond formation have attracted a great deal of attention due to their ease of use and low cost. This report represents a novel and metal-free synthesis of 3,3'-bisimidazopyridinylmethanes via intermolecular oxidative C(sp(2))-H bond functionalization of imidazo[1,2-a]pyridines with dimethyl sulfoxide as the carbon synthon (CH2) using H2O2 as a mild oxidant under air. A library of 3,3'-bis(2-arylimidazo[1,2-a]pyridin-3-yl)methanes has been achieved in good to excellent yields. The present methodology has been successfully applied to imidazo[2,1-b]thiazoles and imidazo[2,1-b]benzothiazoles. Furthermore, the current approach was also extended for the synthesis of unsymmetrical 3,3'-bisimidazopyridinylmethanes under optimized reaction conditions. A mechanistic pathway is proposed on the basis of experiments with radical scavengers and DMSO-d6 and ESI-MS observations.
authors.affiliation: Medicinal and Process Chemistry Division, CSIR-Central Drug Research Institute , BS-10/1, Sector 10, Jankipuram Extension, Sitapur Road, Lucknow 226031, India.
authors.forename: Om P S
authors.initials: OP
authors.lastname: Patel
authors.affiliation: Medicinal and Process Chemistry Division, CSIR-Central Drug Research Institute , BS-10/1, Sector 10, Jankipuram Extension, Sitapur Road, Lucknow 226031, India.
authors.forename: Devireddy
authors.initials: D
authors.lastname: Anand
authors.affiliation: Medicinal and Process Chemistry Division, CSIR-Central Drug Research Institute , BS-10/1, Sector 10, Jankipuram Extension, Sitapur Road, Lucknow 226031, India.
authors.forename: Rahul K
authors.initials: RK
authors.lastname: Maurya
authors.affiliation: Medicinal and Process Chemistry Division, CSIR-Central Drug Research Institute , BS-10/1, Sector 10, Jankipuram Extension, Sitapur Road, Lucknow 226031, India.
authors.forename: Prem P
authors.initials: PP
authors.lastname: Yadav