Transition metal- and oxidant-free [3 + 2] cyclization of azomethine imines utilizing vinylene carbonate as dual synthons

Abstract

A transition metal- and oxidant-free C-C/C-N annulation of azomethine imines with vinylene carbonate as dual synthons under simple reaction conditions is described herein. Depending on the structure of azinium-N-imines, vinylene...

DBU‐Promoted [3+2] Cyclization/Retro‐Mannich Cascade Reaction of N‐Aminoisoquinolinium and N‐Aminoquinolinium Derivatives with para‐Quinone Methides

“…Building on this foundation, our recent work has expanded these applications. We have reported a [3+2] cyclization of N ‐iminopyridinium salts to synthesize pyrazolo[1,5‐ a ]pyridine and pyrazolo[1,5‐ a ]pyridin‐2‐ol derivatives, employing vinyl carbonate as an ethynol surrogate and acetylene surrogate, respectively (Scheme 1a) [7a] . Subsequently, we introduced a mechanochemical synthesis of 1,2,4‐triazoles through a [3+2] cycloaddition of azinium‐ N ‐imines with nitriles (Scheme 1b) [7b] .…”

Advancement of vinylene carbonate as a coupling partner in metal-catalyzed C–H functionalization

“…Apart from the aforementioned transition metal-catalyzed cyclization reactions, in 2022, Liu and coworkers reported a [3 + 2] cyclization reaction of azomethine imines with VC under mild reaction conditions without the need for both transition metals and oxidants (Scheme 18). 65 Using the VC reagent as both an ethynol and acetylene surrogate allows for the formation of pyrazolo[1,5- a ]pyridin-2-ol 59 and pyrazolo[1,5- a ]pyridine 61 derivatives through [3 + 2] cyclization depending on the structural characteristics of the azonium- N -imines. This system could be applied to a diverse range of heterocyclic N -imines such as quinolinium and isoquinolinium salts.…”

Vinylene Carbonate as Synthon in Transition Metal‐Catalyzed C−H Bond Activation/Annulation Reactions

“…Very recently, a C−C/C−N cyclization reaction of vinylene carbonate with azinium‐N‐imines in the absence of transition metal and oxidant was developed by the Liu′s and Cao′s group, in which vinylene carbonate is used as an acetylene substitute to obtain pyrazolo[1,5‐ a ]pyridines (Scheme 23). [41] …”