Pyridine Derivatives as Insecticides: Part 6. Design, Synthesis, Molecular Docking, and Insecticidal Activity of 3-(Substituted)methylthio-5,6,7,8-tetrahydroisoquinoline-4-carbonitriles Toward Aphis gossypii ( Glover , 1887).

Three new series of 3-(substituted)methylthio-4-cyano-5,6,7,8-tetrahydroisoquinolines were designed and synthesized starting from readily available materials, 7-acetyl-4-cyano-1,6-dimethyl-6-hydroxy-8-(4-pyridyl, 3-pyridyl, phenyl, 4-methoxyphenyl, or 4-chlorophenyl)-5,6,7,8-tetrahydrosoquinoline-3(2 H )-thiones 2a - e in high yields and very pure states. Thus, compounds 2a - e were reacted with some chloro reagents, namely, N -aryl-2-chloroacetamides 3a - f and N -(naphthalen-2-yl)-2-chloroacetamide ( 3g ) under mild basic conditions to give the first two series of the target compounds, 3-( N -aryl)carbamoylmethylthio-5,6,7,8-tetrahydroisoquinoline-4-carbonitriles 4a - l and 5a - e , respectively. Reaction of compounds 2d , e with ethyl chloroacetate under the same conditions gave the other series, 3-ethoxycarbonyl-methylthio-5,6,7,8-tetrahydroisoquinoline-4-carbonitriles 6d , e . Structural formulas of all of the new compounds were elucidated and confirmed by elemental and spectral analyses. The insecticidal activity of all synthesized 5,6,7,8-tetrahydrosoquinolines toward the nymphs and adults of Aphis gossypii were screened. The results revealed the promising insecticidal activity of some tested compounds. Moreover, the structure-activity relationships as well as molecular docking of some representative compounds were evaluated.