Pyridine Derivatives\nas Insecticides: Part 6. Design,\nSynthesis, Molecular Docking, and Insecticidal Activity of 3‑(Substituted)methylthio-5,6,7,8-tetrahydroisoquinoline-4-carbonitriles\nToward <i>Aphis gossypii</i> (<i>Glover<

Three\nnew series of 3-(substituted)methylthio-4-cyano-5,6,7,8-tetrahydroisoquinolines\nwere designed and synthesized starting from readily available materials,\n7-acetyl-4-cyano-1,6-dimethyl-6-hydroxy-8-(4-pyridyl, 3-pyridyl, phenyl,\n4-methoxyphenyl, or 4-chlorophenyl)-5,6,7,8-tetrahydrosoquinoline-3(2<i>H</i>)-thiones <b>2a</b>–<b>e</b> in high\nyields and very pure states. Thus, compounds <b>2a</b>–<b>e</b> were reacted with some chloro reagents, namely, <i>N</i>-aryl-2-chloroacetamides <b>3a</b>–<b>f</b> and <i>N</i>-(naphthalen-2-yl)-2-chloroacetamide (<b>3g</b>) under mild basic conditions to give the first two series\nof the target compounds, 3-(<i>N</i>-aryl)carbamoylmethylthio-5,6,7,8-tetrahydroisoquinoline-4-carbonitriles <b>4a</b>–<b>l</b> and <b>5a</b>–<b>e</b>, respectively. Reaction of compounds <b>2d</b>,<b>e</b> with ethyl chloroacetate under the same conditions gave\nthe other series, 3-ethoxycarbonyl-methylthio-5,6,7,8-tetrahydroisoquinoline-4-carbonitriles <b>6d</b>,<b>e</b>. Structural formulas of all of the new compounds\nwere elucidated and confirmed by elemental and spectral analyses.\nThe insecticidal activity of all synthesized 5,6,7,8-tetrahydrosoquinolines\ntoward the nymphs and adults of Aphis gossypii were screened. The results revealed the promising insecticidal activity\nof some tested compounds. Moreover, the structure–activity\nrelationships as well as molecular docking of some representative\ncompounds were evaluated.