A novel synthesis of triazolo[1,2-a]indazole-1,3,8-trione derivatives by reaction of urazole, dimedone and aromatic aldehydes under conventional heating and microwave irradiation and solvent-free conditions using silica nanoparticles prepared from rice husk ash as catalyst is described. The new method features high yields, multicomponent reactions and environmental friendliness.

A very short synthesis (5 steps), the crystal structure and resolution of an elaborate, inherently chiral [n](1,6)pyrenophane is reported. The synthesis hinges upon two very productive events: a multicomponent reaction and an unprecedented double-McMurry/valence isomerization/dehydrogenation step. Aromatization reactions are involved in the formation of all four of the rings of the pyrene system.