Three new series of isoquinolines, that is, 7-acetyl-3-acetonylsulfanyl-8-aryl-1,6-dimethyl-6-hydroxy-5,6,7,8-tetrahydroisoquinoline-4-carbonitriles
(3a–c); 3-acetonylsulfanyl-8-aryl-1,6-dimethyl-7,8-dihydroisoquinoline-4-carbonitriles
(4a–c); and 7-acetyl-8-aryl-1,6-dimethyl-3-ethylsulfanyl-7,8-dihydroisoquinoline-4-carbo-nitriles
(6a,b) were carefully synthesized. Also,
pyrazoloisoquinoline 7 was used as a precursor for synthesis
of 7-ethylsulfanyl-4-phenyl-1-thiocarbamoyl-3,5,9a-trimethyl-3a,4,9,9a-tetrahydro-1H-pyrazolo[3,4-g]isoquinoline-8-carbonitrile (8); 7-benzyl-sulfanyl-4-phenyl-1-thiocarbamoyl-3,5,9a-trimethyl-3a,4,9,9a-tetrahydro-1H-pyrazolo[3,4-g]isoquinoline-8-carbonitrile
(9); and 7-ethylsulfanyl-1-(4-oxo-4,5-dihydrothiazol-2-yl)-4-phenyl-3,5,9a-trimethyl-3a,4,9,9a-tetrahydro-1H-pyrazolo[3,4-g]isoquinoline-8-carbonitrile
(10). Moreover, the crystal structures of two representative
compounds were determined. Eleven new compounds 3a, 4a, 3b, 4b, 3c, 4c, 6a, 6b, 8, 9, and 10 were screneed for their toxicological
activity against nymphs and adults of Aphis gossypii by using acetamprid, as a reference. After 24 h of treatment, the
bioefficacy results indicate that all tested isoquinolines exhibit
toxicological activity that varied from very high to low against nymphs
and adults of Aphis gossypii, some compounds showing
activity near to that of acetampirid and only one compound which possesses
higher activity against nymphs and adults of Aphis gossypii than that of acetampirid itself.