Solvent-free Synthesis and DFT Studies on Mechanistic Pathway of 4-Aryl-4,10-Dihydroindeno[1,2-b]Pyrazolo[4,3-e]Pyridin-5(1H)-ones

A novel, efficient, and grind stone procedure for the synthesis of pyrazolo[4,3-e]pyridine compounds at room temperature was reported. This methodology offers several advantages such as mild conditions, excellent yields, simple procedure, and reduced environmental consequences. The structures of synthesized 4-Aryl-4,10-dihydroindeno[1,2-b]pyrazolo[4,3-e]pyridin-5(1H)-ones were confirmed by 1H, 13C NMR, and FTIR spectral data and elemental analyses. The one-pot three-component condensation of various benzaldehydes, indandione, and 3-amino-5-methylpyrazole was investigated at the B3LYP/6-311G** level to explore the reaction mechanism as a theoretical study. All of routes were studied, structure of intermediates was optimized, and all of respective transition states were found. The calculation results proved that the proposed mechanism consists of four intermediates.