Structure-Activity Studies of Insecticidal 2-Methoxy-1,3,2-oxazaphospholidine 2-Sulfides against Musca domestica and Tribolium castaneum

Abstract

2-Methoxy-5-substituted 1,3,2-oxazaphospholidine 2-sulfides (5-RMOS) were prepared by reacting methyl phosphorodichloridothionate with appropriate aminoalcohols which had been synthesized from the corresponding aldehydes with a) trimethylsilyl cyanide, b) sodium bisulfite-pottasium (sodium) cyanide and reacted with lithium aluminum hydride, or from c) phenacyl bromides (chlorides) via hexamethylenetetramine complex followed by acid-catalyzed hydrolysis and reduction with sodium borohydride. 2-Methoxy-5-phenyl-1,3,2-oxazaphospholidine 2-sulfide (5-PMOS, II-l) was the most potent insecticide against Musca domestica by topical application (LD50 = 0.035 μg/fly), whereas 4-methylphenyl (11–45), 4-ethylphenyl (11–51), 4-isopropylphenyl (11–52) and 2,3-dimethoxyphenyl (II-57) analogs of 5-PMOS were the most potent in reducing the larval weight gain of Tribolium castaneum (I50 = 5.5, 3.7, 5.2 and 6.6 ppm). According to the quantitative structure-activity relationship (QSAR) analysis by Hansch and Fujita, steric nature of a substituent is important, and the smaller the substituent at the 5-phenyl of 5-RMOS, the more potent the insecticidal activity toward M. domestica, whereas toward T. castaneum, electronic nature was important, and the more resistant to hydrolysis the compounds, the more potent the activity on larval weight-gain inhibition of T. castaneum. © 1990, Pesticide Science Society of Japan. All rights reserved.