Sulfamic acid catalyzed oxonium-ene reactions under ball milling conditions: Straightforward access to highly functionalized Oxabicyclo[3.2.1]octenes

Abstract Herein, we report a facile green procedure for the synthesis of oxabicyclo[3.2.1]octenes using sulfamic acid as catalyst under solvent-free ball milling conditions. A series of aldehydes or epoxides underwent oxonium-ene reaction with (−)-terpinen-4-ol under optimized conditions to produce a variety of oxabicyclo[3.2.1]octene derivatives. The excellent selectivity, higher isolated yields of the products, use of mild catalyst and solvent-free ball milling conditions, and recyclability are the major advantages of the present procedure.