A simple and clean method for multicomponent synthesis of spiro [indole-tetrahydropyrano(2,3-d)pyrimidine] derivatives using SBA-Pr-SO3H as catalyst under solvent-free conditions

Sulfonic acid functionalized SBA-15 (SBA-Pr-SO₃H) as a new nanoporous solid acid catalyst was applied in the green one-pot synthesis of spiro[indole-tetrahydropyrano(2,3-d)pyrimidine] derivatives via three-component reaction of isatins, malononitrile or cyanoacetic esters and barbituric acids under solvent-free conditions. SBA-Pr-SO₃H was proved to be an efficient heterogeneous nanoporous solid acid catalyst with a pore size of 6 nm, which could be easily handled and removed from the reaction mixture by simple filtration and can be recovered and reused several times without any loss of activity. The advantages of this methodology are high product yields, being environmentally benign, short reaction times, and easy handling.