Alkyl 2-chloro-2-cyclopropylideneacetates - Remarkably versatile building blocks for organic synthesis

Strain in small rings has evolved as one of the principles used to control reactivity and chemoselectivity in transformations of organic compounds. The combination of small rings with multiple bonds and functional groups establishes composite functionalities which demonstrate unique multiple reactivity and thereby potentially high synthetic utility. This survey concentrates on a family of compounds which combines the chemistry of methylenecyclopropanes and that of electron-acceptor-activated alkenes, namely alkyl 2-chloro-2-cyclopropylideneacetates of types 1-3. This special feature makes the compounds 1-3 multifunctional as well as highly reactive, and thus extremely versatile building blocks for organic synthesis. Not only is the general synthetic access to methylenecyclopropanes 1-3 presented here, but particularly their rich chemistry as highly reactive Michael accepters, dienophiles, dipolarophiles and general cyclophiles which leads to a wide range of different types of functionally substituted cyclopropane derivatives, spirocyclopropane-annelated hetero- and carbocycles, mono- and oligocondensed cycles, natural and unnatural amino acids and peptidomimetics, and more. Finally, the first results obtained with polymer-bound substrates of types 1-3 in a combinatorial approach to libraries of potentially biologically active compounds are presented

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