Synthesis of sulfur containing dihydro-pyrrolo derivatives and their biological evaluation as antioxidants

Azomethine Ylides-Versatile Synthons for Pyrrolidinyl-Heterocyclic Compounds

Azomethine ylides are nitrogen-based three-atom components commonly used in [3+2]-cycloaddition reactions with various unsaturated 2π-electron components. These reactions are highly regio- and stereoselective and have attracted the attention of organic chemists with respect to the construction of diverse heterocycles potentially bearing four new contiguous stereogenic centers. This review article complies the most important [3+2]-cycloaddition reactions of azomethine ylides with various olefinic, unsaturated 2π-electron components (acyclic, alicyclic, heterocyclic, and exocyclic ones) reported over the past two decades.

Rh(I)-catalysed imine-directed C-H functionalization via the oxidative [3 + 2] cycloaddition of benzylamine derivatives with maleimides

The Rh(I)-catalysed imine-directed oxidative [3 + 2] cycloaddition of benzylamines with maleimides is reported. A wide range of both benzylamines and maleimides is applicable to the reaction. A one-pot three component strategy using benzylamines, 2-pyridinecarboxaldehyde, and maleimides is successfully achieved. Mechanistic studies including deuterium labelling experiments suggest that a zwitterionic intermediate is formed and is a key intermediate through the Rh-catalysed activation of a benzylic C(sp³)-H bond of the imine.

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.

Biological activity of two new pyrrole derivatives against stored-product species: influence of temperature and relative humidity

Members of the pyrrole group are likely to have interesting properties that merit additional investigation as insecticides at the post-harvest stages of agricultural commodities. In the present work, the insecticidal effect of two new pyrrole derivatives, ethyl 3-(benzylthio)-4,6-dioxo-5-phenyl-2,4,5,6-tetrahydropyrrolo[3,4-c]pyrrole-carboxylate (3i) and isopropyl 3-(benzylthio)-4,6-dioxo-5-phenyl-2,4,5,6-tetrahydropyrrolo[3,4-c]pyrrole-carboxylate (3k) were studied as stored-wheat protectants against two major stored-product insect species, the confused flour beetle, Tribolium confusum Jaquelin du Val adults and larvae and the Mediterranean flour moth, Ephestia kuehniella Zeller larvae at different doses (0.1, 1 and 10 ppm), exposure intervals (7, 14 and 21 days), temperatures (20, 25 and 30°C) and relative humidity (55 and 75%) levels. For T. confusum adults, in the case of the pyrrole derivative 3i, mortality was low and it did not exceed 32.2% in wheat treated with 10 ppm 3i at 30°C and 55% relative humidity. Progeny production was very low (<1 individual/vial) in all combinations of 55% relative humidity, including control. In the case of the pyrrole derivative 3k, mortality reached 67.8% at 30°C and 55% relative humidity in wheat treated with 10 ppm after 21 days of exposure. Progeny production was low in all tested combinations (≤0.7 individuals/vial) of 55% relative humidity, including control. For T. confusum larvae, in the case of the pyrrole derivative 3i, at the highest dose, mortality was 82.2% at 25°C and 55% relative humidity whereas in the case of 3k it reached 77.8% at the same combination. In contrast, mortality at 75% relative humidity remained very low and did not exceed 13.3%. For E. kuehniella larvae, the highest mortalities, 44.4 and 63.3%, were observed in 10 ppm at 25°C and 55% relative humidity for both pyrrole derivatives. The compounds tested here have a certain insecticidal effect, but this effect is moderated by the exposure, the target species, the temperature and the relative humidity.

Highly efficient and diastereoselective synthesis of new pyrazolylpyrrolizine and pyrazolylpyrrolidine derivates by a three-component domino process

Diastereoselective reactions between 4-formylpyrazoles, N-substituted maleimides and glycine derivates led to new series of pyrazolyldipyrrolo [3,4-a:3',4'-f]pyrrolizines and pyrazolylpyrrolo[3,4-c]pyrroles in good yields. The reactions proceeded by a domino process through azomethine ylides formed in situ via a 1,3-dipolar cycloaddition reaction.

Design and synthesis of novel D-ring fused steroidal heterocycles

Using dehydroepiandrosterone as the starting material, we have synthesized a series of steroid analogs possessing a D-ring fused with heterocycles which are pyridine, imidazo [2,1-b]thiazoles or substituted thiazole imines. All the final structures are first reported and identified by NMR and MS spectroscopys, the yields of these products are moderate to good and the reaction conditions are mild. The cytotoxicity of the synthesized compounds against EC-109(human esophageal carcinoma), EC-9706(human esophageal carcinoma), MGC-803(human gastric carcinoma) were investigated.

Two methyl 3-(1H-pyrazol-4-yl)octahydropyrrolo[3,4-c]pyrrole-1-carboxylates form different hydrogen-bonded sheets

In the molecules of both methyl (1RS,3SR,3aRS,6aSR)-1-methyl-3-(3-methyl-1-phenyl-1H-pyrazol-4-yl)-4,6-dioxo-5-phenyloctahydropyrrolo[3,4-c]pyrrole-1-carboxylate, C₂₅H₂₄N₄O₄, (I), and methyl (1RS,3SR,3aRS,6aSR)-5-(4-chlorophenyl)-1-methyl-3-(3-methyl-1-phenyl-1H-pyrazol-4-yl)-4,6-dioxooctahydropyrrolo[3,4-c]pyrrole-1-carboxylate, C₂₅H₂₃ClN₄O₄, (II), the two rings of the pyrrolopyrrole fragment are both nonplanar, with conformations close to half-chair forms. The overall conformations of the molecules of (I) and (II) are very similar, apart from the orientation of the ester function. The molecules of (I) are linked into sheets by a combination of an N-H∙∙∙π(pyrrole) hydrogen bond and three independent C-H∙∙∙O hydrogen bonds. The molecules of (II) are also linked into sheets, which are generated by a combination of an N-H∙∙∙N hydrogen bond and two independent C-H∙∙∙O hydrogen bonds, weakly augmented by a C-H∙∙∙π(arene) hydrogen bond.