Catalyst- and solvent-free Csp2–H functionalization of 4-hydroxycoumarins via C-3 dehydrogenative aza-coupling under ball-milling

A mechanochemistry-driven green and efficient synthetic protocol for bio-relevant coumarin-hydrazones from a one-pot three-component reaction between 4-hydrocoumarins, primary aromatic amines and tert-butyl nitrite under ball-milling has been developed.