Water-triggered union of multi-component reactions towards the synthesis of a 4 H -chromene hybrid scaffold.

An unprecedented union of multi-component reactions to construct pyrazole- and pyranopyrazole-adorned 4 H -chromene from simple reactants in water at ambient temperature is reported. This innovative tactic has integrated two distinct four-component reactions (4CRs) that occur transiently to form four new heterocycles via ten covalent bonds in a single step.