1,2,4-Triazolo[1,5-a]pyrimidines in drug design

Annulation of Hydrazones and Alkynes via Rhodium(III)-Catalyzed Dual C-H Activation: Synthesis of Pyrrolopyridazines and Azolopyridazines

Hydrazones readily synthesized from N-aminopyrroles or N-aminoazoles and aldehydes undergo Rh(III)-catalyzed dual C-H activation and coupling with aryl- and alkyl-substituted alkynes to give pyrrolopyridazines or azolopyridazines, respectively. This transformation represents a rare example of hydrazoyl C-H activation and proceeds without heteroatom functionality to direct C-H activation. Hydrazones derived from aromatic, alkenyl, and aliphatic aldehydes were effective inputs, and tethering the alkyne to the hydrazone enabled annulations to more complex, tricyclic products.

1H,4H-Piperazine-diium Dichlorosulfonate: Structure Elucidation and its Dual Solvent–Catalyst Activity for the Synthesis of New Dihydro-[1,2,4]triazolo[1,5-a]pyrimidine Scaffolds

A new ionic liquid containing a 1H,4H-piperazine-diium ring and chlorosulfonate as a 1,4-dicationic core and counter ion, respectively, was designed and synthesised. The structure elucidation of this ionic liquid was conducted by 1D and 2D NMR, FT-IR, Raman, and mass spectrum analysis. The physical properties of this ionic liquid were determined and reported. Furthermore, the dual solvent–catalyst activity of piperazine-1,4-diium dichlorosulfonate was investigated for the synthesis of new dihydro[1,2,4]triazolo[1,5-a]pyrimidines through a one-pot three-component reaction. The ionic liquid was retrieved and reused several times without reducing its catalytic efficiency.