Synthesis of a SO₃H-bearing carbonaceous solid catalyst, PEG-SAC: Application for the easy access to a diversified library of pyran derivatives

A SO₃H-bearing carbonaceous solid catalyst (PEG-SAC) has been synthesized through sulfonation followed by a hydrothermal carbonization method from renewable resources like polyethylene glycol. The biodegradable catalyst was characterized by XRD, TEM, FT-IR and EDX. The surface area and pore diameter of the catalyst were determined from a nitrogen adsorption-desorption isotherm experiment. A highly convergent, efficient and practical PEG-SAC catalyzed heteroannulation protocol for the synthesis of a library of diversified pyran fused heterocyclic scaffolds has been demonstrated. This synthesis was established to follow the group-assistant-purification (GAP) chemistry process, which can avoid traditional chromatography. A recrystallization purification appeared to be a very good alternative to the traditional classical methods, demonstrating that a carbon-based catalyst is very effective in producing pyran fused heterocyclic molecules. The aqueous reaction medium, easy recovery of the catalyst and high yield of the products make the protocol attractive, sustainable and economic.