Hypervalent Iodine(III)‐Mediated Counteranion Controlled Intramolecular Annulation of Exocyclic β‐Enaminone to Carbazolone and Imidazo[1, 2‐a]pyridine Synthesis. Issue 23 (1st April 2019)

• Record Type: Journal Article
• Authors: Bhattacherjee, Dhananjay; Ram, Shankar; Chauhan, Arvind Singh; Yamini, ; Sheetal, ; Das, Pralay
• Is Part Of: Chemistry. Volume 25:Issue 23(2019)
• Page Start: 5934
• Page End: 5939
• Publication Date: 2019-04-01
• Subjects: annulation -- hypervalent compounds -- iodine -- metathesis -- nitrogen heterocycles; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201806299
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: A highly efficient and flexible protocol for intramolecular annulation of exocyclic β‐enaminones has been disclosed for the synthesis of carbazolones and imidazo[1, 2‐ a ]pyridines through a counter‐anion‐controlled free‐radical mechanism promoted by hypervalent iodine(III). The cooperative behavior of HTIB and AgSbF6 plays a crucial role in the intramolecular annulation process through C−C and C−N bond formation to give the desired products. The mechanistic insights suggest that the two competitive reactions involved in the system are guided by the nature of the counteranion, which determines the formation of the final products. A wide variety of carbazolones and imidazo[1, 2‐ a ]pyridine molecules have been prepared and isolated in good to excellent yields. Abstract : A unique reagent system : A cooperative behavior of two reagent systems is described for the intramolecular annulation of exocyclic β‐enaminones (see scheme). The single reagent system is highly efficient for C−C as well as C−N bond formation processes. Moreover, the specific behavior of different counteranions for the final product formation has been evaluated based on spectroscopic evidence.