Accessing polysubstituted oxazolidines, pyrrolidines and imidazolidines by regioselective [3+2] annulations of ketenimines with donor-acceptor oxiranes and aziridines

Efficient [3 + 2] annulations of N-aryl-C,C-diphenyl ketenimines with metallo-carbonyl and metallo-azomethine ylides, generated via the respective Yb(OTf)3 and Y(OTf)3 promoted carbon–carbon bond heterolysis of donor–acceptor oxiranes and aziridines, have been accomplished. These reactions proceeded under mild conditions and supplied a general methodology for the regioselective construction of structurally complex oxazolidines and pyrrolidines. Moreover, heating neat mixtures of N-aryl-C,C-diphenyl ketenimines and diethyl aziridine-2,3-dicarboxylates led to imidazolidine derivatives. A computational study concluded in stepwise mechanisms for these [3 + 2] annulations, also shedding light on their regioselectivity, concerning which of the two cumulated double bonds of the ketenimine becomes involved in the reaction with the ylide

Exploring the Conversion of Macrocyclic 2,2 '-Biaryl Bis(thioureas) into Cyclic Monothioureas: An Experimental and Computational Investigation

Macrocyclic bis(thioureas) derived from 2,2’-biphenyl and binaphthyl skeletons have been synthesized by reaction of 2,2’-diaminobiaryl and 2,2’-bis(isothiocyanato)biaryl derivatives. The splitting of these bis(thioureas) into two units of the respective cyclic monothioureas has been monitored by NMR, shedding some light on the factors that control these processes. Additionally, a computational study revealed up to three mechanistic paths for the conversion of the 2,2’-biphenyl-derived bis(thiourea) into the corresponding monothiourea. The proposed mechanisms account for the participation of a molecule of water as an efficient proton-switch, as well as for different classes of putative intermediates. The computational study also supports the ability of the thiourea group to participate in a plethora of processes, such as prototropic equilibria, sigmatropic shifts, heteroene and retro-heteroene reactions, and cis-trans isomerizations

Unlocking the synthetic potential of aziridine and cyclopropane-fused quinolin-2-ones by regioselective fragmentation of its three-membered rings

The cyclization of cis-2-(2-azidophenyl)-1-benzyl-3-ethoxycarbonylaziridines and trans-2-(2-azidophenyl)-3-nitrocyclopropane-1,1-dicarboxylates yielded the respective aziridino[2,3-c]quinolin-2-ones and cyclopropa[c]quinolin-2-ones. Ring-opening of the aziridine-fused species under silica gel catalysis provided 3-aminoquinolin-2-ones whereas the ring-expansion of the cyclopropane-fused derivatives by the action of sodium hydride gave 1-benzazepin-2-ones, in both cases in a regioselective manner. A computational study using DFT methods revealed that the mechanism for the transformation of cyclopropa[c]quinolin-2-ones into 1-benzazepin-2-ones involves the initial deprotonation step of its amide function followed by two pericyclic events: a 6π-electrocyclic ring opening and a subsequent [1,5]-H shift

Changes in Soil Microbial Community Structure Influenced by Agricultural Management Practices in a Mediterranean Agro-Ecosystem

Agricultural practices have proven to be unsuitable in many cases, causing considerable reductions in soil quality. Land management practices can provide solutions to this problem and contribute to get a sustainable agriculture model. The main objective of this work was to assess the effect of different agricultural management practices on soil microbial community structure (evaluated as abundance of phospholipid fatty acids, PLFA). Five different treatments were selected, based on the most common practices used by farmers in the study area (eastern Spain): residual herbicides, tillage, tillage with oats and oats straw mulching; these agricultural practices were evaluated against an abandoned land after farming and an adjacent long term wild forest coverage. The results showed a substantial level of differentiation in the microbial community structure, in terms of management practices, which was highly associated with soil organic matter content. Addition of oats straw led to a microbial community structure closer to wild forest coverage soil, associated with increases in organic carbon, microbial biomass and fungal abundances. The microbial community composition of the abandoned agricultural soil was characterised by increases in both fungal abundances and the metabolic quotient (soil respiration per unit of microbial biomass), suggesting an increase in the stability of organic carbon. The ratio of bacteria:fungi was higher in wild forest coverage and land abandoned systems, as well as in the soil treated with oat straw. The most intensively managed soils showed higher abundances of bacteria and actinobacteria. Thus, the application of organic matter, such as oats straw, appears to be a sustainable management practice that enhances organic carbon, microbial biomass and activity and fungal abundances, thereby changing the microbial community structure to one more similar to those observed in soils under wild forest coverage

Threats to soil biodiversity - global and regional trends

Using the information provided on the main threats in the ten ecoregions present in the six world regions (Table of threats for Sub-Saharan Africa, South West Pacific, Latin America and Caribbean, North Africa and Near East, North America and Europe; FAOand ITPS, 2015), a summary table of the main threats common to these ecoregions was produced. This exercise showed that the most widespread threat to soil biodiversity in the world was the loss of SOM and SOC, and that this could be associated with other threats such as deforestation and agricultural intensification (both linked withland use change) and with climate change (particularly in tundra). This clearly shows the importance of sustainable management and conservation practices, to maintain this resource in soils, which represents one of the bases for the soils food webs. Deforestation and agricultural intensification were also major threats worldwide, being important intropical and temperate broad leaf and mixed forests and temperate and montane grassland sand boreal forests/taiga, although the level of available information on the topic was highly variable, depending on the particular world regions where these ecoregions occur. The ecoregions with the highest number of threats were the deserts and dry shrublands, the tropical and subtropical grasslands, and the temperate broad leaf and mixed forests. Invasive species also represented an important threat, particularly in Mediterranean and temperate forests and tundra.Fil: Brown, George. Ministerio da Agricultura Pecuaria e Abastecimento de Brasil; BrasilFil: Cooper, Miguel. Universidade do Sao Paulo. Escola Superior de Agricultura Luiz de Queiroz; BrasilFil: Kobayashi, Mónica. Food And Agriculture Organization Of The United Nations; ItaliaFil: Orgiazzi, Alberto. No especifíca;Fil: Domínguez, Anahí. Universidad Nacional de Río Cuarto. Facultad de Ciencias Exactas Fisicoquímicas y Naturales. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente; ArgentinaFil: Dias Turetta, Ana Paula. No especifíca;Fil: Franco, André. No especifíca;Fil: Zaitsev, Andrey. No especifíca;Fil: Winding, Anne. No especifíca;Fil: Foereid, Bente. No especifíca;Fil: Singh, Brajesh. No especifíca;Fil: Guerra, Carlos. No especifíca;Fil: Rojas, Claudia. No especifíca;Fil: Spurgeon, David. No especifíca;Fil: Aksoy, Ece. No especifíca;Fil: Moreira, Fátima Maria. No especifíca;Fil: Bautista, Francisco. No especifíca;Fil: Xu, Jianming. No especifíca;Fil: Rousk, Johannes. No especifíca;Fil: Bedano, José Camilo. Universidad Nacional de Rio Cuarto. Facultad de Cs.exactas Fisicoquimicas y Naturales. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente. - Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Cordoba. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente.; ArgentinaFil: Bagyaraj, Joseph D.. No especifíca;Fil: Saxena, Krishna. No especifíca;Fil: da Silva, Laura Fernanda Simões. No especifíca;Fil: Tedersoo, Leho. No especifíca;Fil: Byrne, Loren. No especifíca;Fil: Callaham, Mac A.. No especifíca;Fil: Choudhary, Madhu. No especifíca;Fil: Aller, M. Fernanda. No especifíca;Fil: Delgado Baquerizo, Manuel. No especifíca;Fil: García Orenes, Maria Fuensanta. No especifíca;Fil: Tsiafouli, Maria. No especifíca;Fil: de Graaf, Marie. No especifíca;Fil: Hart, Miranda. No especifíca;Fil: Thuita, Moses. No especifíca;Fil: Karanja, Nancy. No especifíca;Fil: Fromin, Nathalie. No especifíca;Fil: Eisenhauer, Nico. No especifíca;Fil: Kaneko, Nobuhiro. No especifíca;Fil: Mele, Pauline. No especifíca;Fil: Pastor, Pilar Andres. No especifíca;Fil: Ochoa-Hueso, Raul. No especifíca;Fil: Kuperman, Roman. No especifíca;Fil: Ichami, Stephen. No especifíca;Fil: Fonte, Steven J.. No especifíca;Fil: Santillan, Vinisa Saynes. No especifíca;Fil: Tapia Torres, Yunuen. No especifíca