“…We previously investigated the metal-free intramolecular alkyne-azide cycloaddition reaction for the formation of the pyrazolo [4,3-f ] [1,2,3]triazolo [5,1-c] [1,4]oxazepine ring system [26] as well as the synthesis of 2,6-dihydropyrano [2,3-c]pyrazole derivatives by employing the ring-closing metathesis (RCM) reaction [27]. In continuation of our interest in the synthesis and investigation of novel pyrazole-containing polyheterocyclic systems [28][29][30][31][32][33], we report herein the synthesis and structural elucidation of new 3a,4dihydro-3H,7H-and 4H,7H-pyrazolo [4 ,3 :5,6]pyrano [4,3-c] [1,2]oxazole derivatives from appropriate 3-(prop-2-en-1-yloxy)-or 3-(prop-2-yn-1-yloxy)-1H-pyrazole-4-carbaldehyde oximes via the intramolecular nitrile oxide cycloaddition reaction.…”