Solvent-free multicomponent reactions using the novel N-sulfonic acid modified poly(styrene-maleic anhydride) as a solid acid catalyst

• Poly(styrene-co-maleic anhydride) was reacted with 4-aminopyridine and used as a polymeric support.
• This support was reacted with chlorosulfonic acid for the preparation of solid acid catalyst.
• A facile methodology for the solvent-free multicomponent reactions for the synthesis of 4H-Pyrimido[2,1-b]benzothiazole derivatives, tetrasubstituted imidazoles and benzoxanthenones were successfully reported.
• This catalyst can promote the yields and reaction times and at least, can be loaded without pre-activation and reused over several repeated runs.

A new N-sulfonic acid based on the polymer-support as a solid acid catalyst is prepared by the reaction of the modified poly(styrene-alt-maleic anhydride) with neat chlorosulfonic acid. 4H-Pyrimido[2,1-b]benzothiazole derivatives, tetrasubstituted imidazoles and benzoxanthenones as selected solvent-free multicomponent reactions were successfully synthesized using this catalyst. These eco-friendly protocols offer several advantages such as green and cost-effective procedures with excellent yield, shorter reaction time, simpler work-up, recovery, and reusability of metal-free solid acid heterogeneous catalyst along with tolerance of a wide range of functional groups.

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