Water‐Triggered Metal‐Free Synthesis of Pyranopyrazoles via One‐Pot Oxidation/Michael Addition/Cyclization/Dehydration Sequence.

An “all water” strategy for the catalyst free chemo‐selective synthesis of pyranopyrazoles via the reaction of 3‐methyl‐1‐phenyl‐1 H ‐pyrazol‐5(4 H )‐one with benzyl alcohols has been developed. Water actuates the reaction via ‘electrophile– nucleophile dual activation’ of the reactants through the concerted hydrogen bonding network and impel the reactants for C−C bond formation. Reaction proceeds by metal and catalyst free oxidation–Michael addition–cyclization–dehydration sequence. This method gave pyrano[2, 3‐c:6,5‐c′]dipyrazol]‐2‐ones selectivity over other possible products. Furthermore, this method is also applied on the reaction of the benzyl alcohols and dimedone to give arylmethylene[bis(5,5‐dimethyl‐3‐hydroxy‐2‐cyclohexene‐1‐ones)] in good to excellent yields.