Nano-cellulose-OSO3H as a new,green, and effective nano-catalyst for one-pot synthesis of pyrano [4,3-b] pyrans

A facile, green, and efficient method has been developed for the synthesis of biologically important pyrano [4,3-b] pyrans in the presence of nano-cellulose-OSO₃H as a new solid acid catalyst. The reaction involves the use of 4-hydroxy-6-methyl-2H-pyran-2-one, malononitrile, and aldehydes. A wide range of aldehydes is compatible in this reaction, producing excellent yields in short time. The morphology of nano-catalyst (nano-cellulose-OSO₃H) was observed using a scanning electron microscopy (SEM). The cellulose-OSO₃H surface was studied by the energy dispersive X-ray spectroscopy (EDX) method to find out the chemical composition. The decomposition steps and thermal stability of the catalyst were investigated by thermal analysis techniques (TGA/DTG). In addition, the vibrational spectrum analysis (FT-IR) and X-ray diffractogram (XRD) of the catalyst have been performed.