Allylic Acetals as Acrolein Oxonium Precursors in Tandem C−H Allylation and [3+2] Dipolar Cycloaddition. Issue 28 (3rd June 2019)

• Record Type: Journal Article
• Authors: Lee, Heeyoung; Kang, Dahye; Han, Sang Hoon; Chun, Rina; Pandey, Ashok Kumar; Mishra, Neeraj Kumar; Hong, Sungwoo; Kim, In Su
• Is Part Of: Angewandte Chemie international edition. Volume 58:Issue 28(2019)
• Page Start: 9470
• Page End: 9474
• Publication Date: 2019-06-03
• Subjects: allylic acetal -- C−H functionalization -- dipolar cycloaddition -- indenopyrazolopyrazolone -- tandem reaction; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201903983
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: The ruthenium(II)‐catalyzed C−H functionalization of (hetero)aryl azomethine imines with allylic acetals is described. The initial formation of allylidene(methyl)oxoniums from allylic acetals could trigger C(sp 2 )−H allylation, and subsequent endo ‐type [3+2] dipolar cycloaddition of polar azomethine fragments to deliver valuable indenopyrazolopyrazolones. The utility of this method is showcased by the late‐stage functionalization of bioactive molecules such as estrone and celecoxib. Combined experimental and computational investigations elucidate a plausible mechanism of this new tandem reaction. Notably, the reductive transformation of synthesized compounds into biologically relevant diazocine frameworks highlights the importance of the developed methodology. Abstract : The ruthenium(II)‐catalyzed C−H allylation of (hetero)aryl azomethine imines with allylic acetals followed by an intramolecular endo ‐type [3+2] dipolar cycloaddition is described. This strategy allows the direct and efficient construction of highly substituted indenopyrazolopyrazolone frameworks in good to high yields.