Synthesis of Ortho-nitrochalcones by solvent-free grinding method: Facilitating the synthesis of 2,3-Disubstituted Quinoline N-oxides via bimolecular reaction

A method for the synthesis of 2,3-disubstituted quinoline N-oxides, ortho-nitrochalcones, and their derivatives is reported. Through mortar-pestle grinding under solvent-free conditions, a series of ortho-nitrochalcone derivatives, naphthalenone derivatives, and indenone derivatives were obtained in good to excellent yields. Additionally, by using ortho-nitrochalcones and their derivatives along with 2-nitrobenzaldehyde as starting materials, in the presence of a specific ratio of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and sodium hydroxide (NaOH), and with 1,2-diphenylhydrazine involved, 2,3-disubstituted quinoline N-oxides were synthesized through a bimolecular reaction. This synthetic approach features metal-free catalysis, employs inexpensive and easily accessible raw materials, and operates under mild reaction conditions, thereby enriching the research domain of organic synthesis.