Site-specific role of bifunctional graphitic carbon nitride catalyst for the sustainable synthesis of 3,3-spirocyclic oxindoles in aqueous media.

Functionalized graphitic carbon nitride (Sg-CN) has been manufactured and used as a reusable catalyst for the one-pot production of various spiro-pyrano chromenes and spiro indole-3,1'-naphthalene tetracyclic systems in aqueous media. An ultrasound-assisted method has been used for the functionalization of g-CN. The catalytic functionalities and the structural integrity of the catalyst were characterized different analytical tools.