Dipyrazolo[1,5-a:4',3'-c]pyridines - a new heterocyclic system accessed via multicomponent reaction.

The synthesis of dipyrazolo[1,5-a:4',3'-c]pyridines is described. Easily obtainable 5-alkynylpyrazole-4-carbaldehydes, p-toluenesulfonyl hydrazide, and an aldehyde or ketone containing an α-hydrogen atom were reacted in a silver triflate catalyzed multicomponent reaction affording new tricyclic compounds with a dipyrazolo[1,5-a:4',3'-c]pyridine core. Detailed NMR spectroscopic investigations ((1)H, (13)C and (15)N) were undertaken with all obtained compounds.