Abstract: 【Aim】 Citronellal has good repellent activity against ants. This study aims to seek novel ant terpenoid repellents. 【Methods】 A series of citronella acetals including citronellal dimethyl acetal, citronellal diethyl acetal, citronellal dipropyl acetal, citronellal diisobutyl acetal, citronellal glycol acetal, citronellal 1,2-propanediol acetal and citronellal 1,3-propanediol acetal were synthesized in this study using citronellal as the starting material. Their structures were characterized with IR, MS, ¹H NMR and ¹³C NMR after purification. The repellent activities of these compounds at different concentrations against the pharaoh ant, Monomorium pharaonis were tested. 【Results】 At the concentration of 10 mg/mL, all the compounds except citronellal dimethyl acetal had the repellent rate of more than 70%, and citronellal diethyl acetal, citronellal glycol acetal and citronellal 1,3-propanediol acetal had the repellent rates of 87.47%, 100% and 97.53%, respectively. When the concentrations of the compounds dropped to 2.5 mg/mL, the repellent activities of five compounds decreased significantly, while citronellal glycol acetal and citronellal 1,3-propanediol acetal still showed high repellent activities with the repellent rates of 85.33% and 97.10%, respectively. Variance analysis showed that citronellal 1,3-propanediol acetal had the strongest repellent effect, followed by citronellal glycol acetal. 【Conclusion】 The results suggest that citronellal diethyl acetal, citronellal glycol acetal and citronellal 1,3-propanediol acetal can be used for repelling M. pharaonis, and citronellal glycol acetal and citronellal 1,3-propanediol acetal can be better choices. This research provides a basic reference for screening good ant repellents.

Key words: Citronellal, acetal derivatives, chemical synthesis, structure characterization, ant repellent, repellent activity, Monomorium pharaonis