An Efficient and Transition Metal-Free Base-Promoted Multi-Component Synthesis of Aza-Fused Polysubstituted Pyrido[2′,3′:3,4]Pyrazolo[1,5-a]Pyrimidine Derivatives

Abstract

An efficient and concise practical protocol for the synthesis of novel aza-fused polysubstituted pyrido[2′,3′:3,4]pyrazolo[1,5-a]pyrimidine derivatives from a readily available aromatic aldehyde, acetophenone and 1H‐pyrazolo[3,4‐b]pyridin‐3‐amine in presence of Ba(OH)₂, under transition metal-free conditions, has been established. This transformation presumably occurs through a sequential Aldol reaction, imine-formation, intramolecular N-cyclization, auto-oxidation sequence of reactions. This protocol, which includes the formation of new C–C and C–N bonds, features a wide substrate scope with a broad range of functional group tolerance.

Graphical Abstract

Keywords:

• Barium hydroxide
• multi-component reaction
• N-fused pyrimidine
• polysubstituted heterocyclics
• transition metal-free

Disclosure statement

No potential conflict of interests was reported by the authors.

Supporting Information S1

Experimental details, ¹H NMR and ¹³C NMR spectra for all compounds were provided as Supplementary Information.