B(iii)-catalyzed synthesis of spirooxindole and dihydro-2-oxopyrrole under solventless conditions in a ball mill, along with DFT computations

Abstract

Mechanochemical synthesis of heterocyclic compounds is a growing research field due to its simplicity and environmental compatibility. Solvent-free mechanochemical reactions using a ball mill not only eliminate the need for bulky solvents and reduce waste but also open the door to the synthesis of various organic compounds, including common drugs. Combining two different acids, including molybdic acid (MoO₃(H₂O)₃ complex structure) and Lewis acid BF₃, is a smart strategy to prepare a new and porous cluster nano-catalyst with high acidic properties (pH = 1). Here, the MoO₃/BF₃ nano-catalyst was prepared. This heterogeneous acidic nano-catalyst was then investigated for the synthesis of derivatives of nitrogen-containing heterocyclic compounds, such as spirooxindoles and dihydro-2-oxopyrroles, using the Michael–Mannich cyclocondensation method under solvent-free mixer Mill conditions. Which is, a green and environmentally friendly method. These results align with the data obtained from the DFT calculations. Total energy and electronic band gap energy (E_g = E_HOMO − E_LUMO) calculations were performed for all dihydro-2-oxopyrrole and spirooxindoles derivatives synthesized in this work. The type of final structure of the catalyst was determined using different analyses such as analyses FT-IR, XRD, FESEM, EDX, EDS-MAP, TEM, BET, and TGA were performed.