Laboratory evaluation of five novel pyrrole derivatives as grain protectants against Tribolium confusum and Ephestia kuehniella larvae

Several naturally discovered or laboratory-synthesized pyrrole compounds have insecticidal, acaricidal and microbial properties. The novel sulfanyl 5H-dihydro-pyrrole derivatives exhibit certain antioxidant activities. However, there is a knowledge gap whether these substances are potent grain protectants against stored-product insect pest species. In this context, we evaluated the insecticidal activity of five novel pyrrole derivatives (under the trivial names 3a, 3g, 3l, 3m, 3h), against larvae of Tribolium confusum Jaquelin du Val and Ephestia kuehniella Zeller at different doses (0.1, 1 and 10 ppm), exposure intervals (7, 14 and 21 days or 1, 2, 7, 14, 21 days), temperatures (20, 25 and 30 °C), relative humidity (RH) (55 and 75 %) levels and commodities (wheat, maize, barley). The pyrrole derivative 3a exhibited the highest insecticidal activity, while 3g, 3l, 3m and 3h caused similar mortality against larvae of T. confusum. Apart of the level of efficacy, all tested pyrrole derivatives performed similarly according temperature. We found that increase in temperature increased mortality in the majority of the tested combinations. Generally, the pyrrole derivatives caused the highest mortality levels at 30 °C. The pyrrole derivatives 3a, 3g, 3l and 3m were affected by relative humidity at almost all combinations tested. The 75 % level of RH moderated the efficacy of the pyrrole derivatives, while the 55 % enhanced it. Mortality of T. confusum and E. kuehniella on maize was much lower on treated maize than barley or wheat. However, 100 % control of both species was recorded only on treated barley. The results of the present study indicate that the pyrrole derivatives tested could serve as grain protectants against noxious stored-product insects under certain biotic and abiotic conditions.Maria C. Boukouvala, Nickolas G. Kavallieratos, Christos G. Athanassiou, Dusan Losic, Lazaros P. Hadjiarapoglou, Yiannis Eleme

Insecticidal efficacy of six new pyrrole derivatives against four stored-product pests

Several pyrrole derivatives exhibit insecticidal activity and can be effective as grain protectants. In the present study, we evaluate the insecticidal efficacy of six novel pyrrole derivatives, namely methyl 3-(methylthio)-4,6-dioxo-5-phenyl-1,3a,4,5,6,6a-hexahydropyrrolo[3,4-c]pyrrole-1 carboxylate (compound syn) (2a-syn), methyl 3-(methylthio)-4,6-dioxo-5-phenyl-1,3a,4,5,6,6a-hexahydropyrrolo[3,4-c]pyrrole-1-carboxylate (compound anti) (2a-anti), methyl 3-(benzylthio)-4,6-dioxo-5-phenyl-1,3a,4,5,6,6a-hexahydropyrrolo[3,4-c]pyrrole-1-carboxylate (compound syn) (2f-syn), methyl 3-(benzylthio)-4,6-dioxo-5-phenyl-1,3a,4,5,6,6a-hexahydropyrrolo[3,4-c]pyrrole-1-carboxylate (compound anti) (2f-anti), methyl 3-(butylthio)-4,6-dioxo-5-phenyl-2,4,5,6-tetrahydropyrrolo[3,4-c]pyrrole-1-carboxylate (3e), and methyl 2-benzyl-3-(methylthio)-4,6-dioxo-5-phenyl-2,4,5,6-tetrahydropyrrolo[3,4-c]pyrrole-1-carboxylate (0665), against four important species infesting stored products, the rice weevil, Sitophilus oryzae (Coleoptera: Curculionidae), the lesser grain borer, Rhyzopertha dominica (Coleoptera: Bostrychidae), the confused flour beetle, Tribolium confusum (Coleoptera: Tenebrionidae), and the Mediterranean flour moth, Ephestia kuehniella (Lepidoptera: Pyralidae). The six pyrrole derivatives were evaluated on wheat at different doses (0.1, 1, and 10 ppm) and exposure intervals (7, 14, and 21 days). For S. oryzae adults, the highest mortality was recorded at 10 ppm of 2a-syn (36.7%) followed by 2f-syn (32.2%) and 2f-anti (27.8%) after 21 days of exposure. Regarding progeny production, the application of the six pyrrole derivatives significantly reduced offspring emergence if compared with the controls. After 21 days, mortality of R. dominica reached 50% testing 10 ppm of 2f-syn, followed by 2a-syn (46.7%), 2f-anti (41.1%), and 2a-anti (33.3%), while for 3e and 0665, mortality remained low, not exceeding 17.8%. Mortality of T. confusum adults was very low, ranging from 0 to 16.7% after 21 days of exposure. Progeny production was low (< 1.7 individuals per vial) for all doses of the tested pyrrole derivatives, including control vials. For 2a-syn, 2a-anti, 2f-anti, and 0665, no progeny production was recorded testing 1 and 10 ppm, while for 2f-syn and 3e, no offspring emergence was noted testing 10 ppm. For T. confusum larvae, after 21 days of exposure, mortality reached 62.2% testing 10 ppm of 3e followed by 0665 (55.6%) and 2a-anti (42.2%). For E. kuehniella larvae, mortality reached 57.8% at 10 ppm of 2a-syn, followed by the pyrrole derivative 2f-anti (43.3%) after 21 days of exposure. Overall, these results show that the efficacy of pyrrole derivatives strongly varied according to the exposure interval, tested dose, treated insect species and developmental instar. The tested pyrrole derivatives, with special reference to 2a-syn, 2a-anti, 2f-syn, 2f-anti and 0665, are slow-acting compounds exerting relevant toxicity on key stored-product pests over time. They can be considered further for assays with selected blends aiming to develop novel control tools against stored-product pests in real-world conditions

Mono- and Binuclear Copper(I) Complexes of Thionucleotide Analogues and Their Catalytic Activity on the Synthesis of Dihydrofurans

The reaction of copper­(I) halides with 2-thiouracil (TUC), 6-methyl-2-thiouacil (MTUC), and 4-methyl-2-mercaptopyrimidine (MPMTH) in the presence of triphenylphosphine (tpp) in a 1:1:2 molar ratio results in a mixed-ligand copper­(I) complex with the formulas [Cu₂(tpp)₄(TUC)­Cl] (<b>1</b>), [Cu₂(tpp)₄(MTUC)­Cl] (<b>2</b>), [Cu­(tpp)₂(MPMTH)­Cl]·¹/₂CH₃OH (<b>3</b>), [Cu­(tpp)₂(MTUC)­Br] (<b>4</b>), and [Cu­(tpp)₂(MTUC)­I]·¹/₂CH₃CN (<b>5</b>). The complexes have been characterized by FT-IR, ¹H NMR, and UV–vis spectroscopic techniques and single-crystal X-ray crystallography. Complexes <b>1</b> and <b>2</b> are binuclear copper­(I) complexes. Two phosphorus atoms from tpp ligands are coordinated to the copper­(I) ions, forming two units that are linked to each other by a deprotonated TUC or MTUC chelating ligand through a sulfur bridge. A linear Cu–S–Cu moiety is formed. The tetrahedral geometry around the metal centers is completed by the nitrogen-donor atom from the TUC or MTUC ligand for the one unit, while for the other one, it is completed by the chloride anion. Two phosphorus atoms from two tpp ligands, one sulfur atom from MPMTH or MTUC ligand, and one halide anion (Cl, Br, and I) form a tetrahedron around the copper ion in <b>3</b>–<b>5</b> and two polymorphic forms of <b>4</b> (<b>4a</b> and <b>4b</b>). In all of the complexes, either mono- or binuclear intramolecular O–H···X hydrogen bonds enhance the stability of the structures. On the other hand, in almost all cases of mononuclear complexes (with the exception of a symmetry-independent molecule in <b>4a</b>), intermolecular NH···O hydrogen-bonding interactions lead to dimerization. Complexes <b>1</b>–<b>5</b> were studied for their catalytic activity for the intermolecular cycloaddition of iodonium ylides toward dihydrofuran formation by HPLC, ¹H NMR, and LC-HRMS spectroscopic techniques. The results show that the geometry and halogen and ligand types have a strong effect on the catalytic properties of the complexes. The highest yield of dihydrofurans was obtained when “linear” complexes <b>1</b> and <b>2</b> were used as the catalysts. The activity of the metal complexes on the copper­(I)-catalyzed and uncatalyzed intramolecular cycloaddition of iodonium ylide is rationalized through electronic structure calculation methods, and the results are compared with the experimental ones

Synthesis and Structural Characterization of New Cu(I) Complexes with the Antithyroid Drug 6‑<i>n</i>‑Propyl-thiouracil. Study of the Cu(I)-Catalyzed Intermolecular Cycloaddition of Iodonium Ylides toward Benzo[<i>b</i>]furans with Pharmaceutical Implementations

The reaction of copper­(I) iodide with 6-<i>n</i>-propylthiouracil (ptu) in the presence or absence of the triphenylphosphine (tpp) or tri­(<i>p</i>-tolyl)­phosphine (tptp) in a 1:1:2 molar ratio forms the mixed ligand Cu­(I) complex with formula [CuI­(ptu)₂]­(toluene) (<b>1</b>), [CuI­(tpp)₂(ptu)] (<b>2</b>), and [CuI­(tptp)₂(ptu)] (<b>3</b>). The complexes have been characterized by FT-IR, ¹H NMR, UV–vis, spectroscopic techniques, and single crystal X-ray crystallography. Two sulfur atoms from two ptu ligands and one iodide form a trigonal geometry around the metal center in <b>1</b>. Intramolecular interactions through hydrogen bonds lead to a bend ribbon polymeric supramolecular architecture with zigzag conformation. Two phosphorus atoms from two arylphosphines, one sulfur atom, and one iodide anion form a tetrahedron around the copper ion in case of <b>2</b> and <b>3</b>. Intramolecular hydrogen bonding interactions lead to dimerization. Complexes <b>1</b>–<b>3</b> and the already known ones with formulas, [(tpSb)₂Cu­(μ₂-I)₂Cu­(tpSb)₂] (<b>4</b>) (tbSb = triphenylstibine), [(tpp)­Cu­(μ₂-I)₂Cu­(tpp)₂] (<b>5</b>), [(tpp)­Cu­(μ₂-Cl)₂Cu­(tpp)₂] (<b>6</b>), [CuCl­(tpp)₃·(CH₃CN)] (<b>7</b>), and [AuCl­(tpp)] (<b>8</b>), were used to study their catalytic activity on the intermolecular cycloaddition of iodonium ylides toward benzo­[<i>b</i>]­furans formation. The results show that both the metal and the ligand type affect the catalytic affinity of the complexes. The highest yield of benzo­[<i>b</i>]­furan was derived when complexes <b>2</b>,<b> 3</b>, and <b>4</b> were used as catalysts. The mechanism of the Cu­(I)-catalyzed and uncatalyzed intramolecular cycloaddition of iodonium ylide has been also thoroughly explored by means of ab initio electronic structure calculation methods, and the results are compared with the experimental ones

Synthesis and Structural Characterization of New Cu(I) Complexes with the Antithyroid Drug 6‑<i>n</i>‑Propyl-thiouracil. Study of the Cu(I)-Catalyzed Intermolecular Cycloaddition of Iodonium Ylides toward Benzo[<i>b</i>]furans with Pharmaceutical Implementations

The reaction of copper­(I) iodide with 6-<i>n</i>-propylthiouracil (ptu) in the presence or absence of the triphenylphosphine (tpp) or tri­(<i>p</i>-tolyl)­phosphine (tptp) in a 1:1:2 molar ratio forms the mixed ligand Cu­(I) complex with formula [CuI­(ptu)₂]­(toluene) (<b>1</b>), [CuI­(tpp)₂(ptu)] (<b>2</b>), and [CuI­(tptp)₂(ptu)] (<b>3</b>). The complexes have been characterized by FT-IR, ¹H NMR, UV–vis, spectroscopic techniques, and single crystal X-ray crystallography. Two sulfur atoms from two ptu ligands and one iodide form a trigonal geometry around the metal center in <b>1</b>. Intramolecular interactions through hydrogen bonds lead to a bend ribbon polymeric supramolecular architecture with zigzag conformation. Two phosphorus atoms from two arylphosphines, one sulfur atom, and one iodide anion form a tetrahedron around the copper ion in case of <b>2</b> and <b>3</b>. Intramolecular hydrogen bonding interactions lead to dimerization. Complexes <b>1</b>–<b>3</b> and the already known ones with formulas, [(tpSb)₂Cu­(μ₂-I)₂Cu­(tpSb)₂] (<b>4</b>) (tbSb = triphenylstibine), [(tpp)­Cu­(μ₂-I)₂Cu­(tpp)₂] (<b>5</b>), [(tpp)­Cu­(μ₂-Cl)₂Cu­(tpp)₂] (<b>6</b>), [CuCl­(tpp)₃·(CH₃CN)] (<b>7</b>), and [AuCl­(tpp)] (<b>8</b>), were used to study their catalytic activity on the intermolecular cycloaddition of iodonium ylides toward benzo­[<i>b</i>]­furans formation. The results show that both the metal and the ligand type affect the catalytic affinity of the complexes. The highest yield of benzo­[<i>b</i>]­furan was derived when complexes <b>2</b>,<b> 3</b>, and <b>4</b> were used as catalysts. The mechanism of the Cu­(I)-catalyzed and uncatalyzed intramolecular cycloaddition of iodonium ylide has been also thoroughly explored by means of ab initio electronic structure calculation methods, and the results are compared with the experimental ones