Ultrasonic‐Assisted Condensation of Aromatic and Aliphatic Aldehydes with 3‐(thiophen‐2‐yl)‐5‐pyrazolone: Synthesis, Characterization and Stereoselective Application

A green and efficient protocol for a one‐pot condensation of 1‐(2,4‐dinitrophenyl)‐3‐(thiophen‐2‐yl)‐1H‐pyrazol‐5(4H)‐one (1) with aromatic and aliphatic aldehydes in different ratios to synthesize novel heterocyclic compounds containing pyrazolone and pyranopyrazole moieties. The reactions were conducted using the ultrasonic and traditional methods. The sonication ensured more efficiency in the rate and yield of the reactions. The structures of the synthesized compounds were elucidated by different spectroscopic methods. Additionally, an enantioselective synthesis of (R)‐ and (S)‐α‐alkylated acid was achieved using 1‐(2,4‐dinitrophenyl)‐4‐(hydroxymethyl)‐3‐(thiophen‐2‐yl)‐1H‐pyrazol‐5(4H)‐one (6) as chiral auxiliary, (S)‐4‐Methyl‐5‐nonanol the aggregation pheromone of red palm weevil was efficiently prepared and used for trapping the red palm weevil.