Contribució de la trifenilfosfina en la catàlisi per espècies de ruteni en addicions de Michael i perfluoroalquilacions d'olefines

Consultable des del TDXTítol obtingut de la portada digitalitzadaUna de les línies d'interès dins el nostre grup de recerca fa referència a la síntesi d'aminoàcids no naturals. Un dels passos clau en aquesta síntesi consisteix en la inducció de asimetria en la funcionalització de compostos b-dicarbonílics. Dins aquest marc d'interès, a l'inici de la tesi doctoral es va dur a terme un estudi per a generar centres quaternaris mitjançant addicions de Michael diastereoselectives, utilitzant diversos inductors de quiralitat, sota catàlisi per RuH2(PPh3)4. Aquest catalitzador de Ru ens va permetre obtenir bons resultats en termes de reactivitat, tot i que no es va aconseguir induir elevada asimetria. Sota catàlisi per un altre complex similar, RuCl2(PPh3)3, no descrit anteriorment com catalitzador en addicions de Michael, es va aconseguir una notable millora en les rendiments, si bé no va millorar la inducció d'asimetria. Aquests resultats ens van conduir a extendre aquest estudi a tota una sèrie de substrats b-dicarbonílics no quirals, aprofitant l'excel·lent activitat catalítica del RuCl2(PPh3)3. Es va realitzar un estudi exhaustiu dels processos catalitzats per aquests complexos de Ru per tal d'intentar establir el mecanisme de la reacció. Durant el transcurs d'aquest estudi es va observar que alguns complexos de Ru que no contenen lligands fosfina (p. ex : (CpRu(N*C-CH3)3PF6), no catalitzaven les addicions de Michael. D'altra banda, es va posar en evidència l'elevada activitat catalítica que presenta la PPh3 en aquestes addicions, fins i tot en condicions sota les quals els complexos RuCl2(PPh3)3 i RuH2(PPh3)4 no mostraven activitat catalítica. Aquestes observacions ens van conduir a concloure que l'espècie responsable de la catàlisi de les addicions de Michael en presència de RuCl2(PPh3)3 i RuH2(PPh3)4, no era una espècie de Ru, sino la PPh3. S'ha proposat una hipòtesi mecanística per les addicions de Michael catalitzades per PPh3 segons la qual la fosfina inicia el procés reaccionant amb l'electròfil d'una manera equivalent a com ho fa en la reacció de Baylis-Hillman i Mitsunobu. En el segon capítol d'aquesta tesi, es van estudiar les perfluoroalquilacions d'olefines, posant un cop més en evidència l'activitat catalítica de la trifenilfosfina en processos suposadament catalitzats per RuCl2(PPh3)3. La trifenilfosfina va catalitzar eficientment l'addició del iodur de perfluorooctil a diverses olefines tant linials com cícliques. Es proposa com a hipòtesi mecanística, un procés radicalari en cadena iniciat per una transferència monoelectrònica. La inhibició de la reacció per addició d'atrapadors radicalaris, així com la manca de reactivitat d'olefines que donen lloc a la formació de radicals estabilitzats per ressonància, són evidències de la naturalesa radiacalària del procès.One of the interest topics in our research group deals with the synthesis of non-natural amino acids. One of the key steps in this synthesis is the asymmetry induction in the functionalization of b-dicarbonyl compounds. For this purpose, we undertook an study of generation of quaternary centres by diastereoselective Michael additions of acetoacetyl derivatives of several chiral inductors under RuH2(PPh3)3 catalysis. We achieved good results in terms of reactivity when working with this ruthenium catalyst, though only moderate asymmetry was induced. Yields improved remarkably when we used as a catalyst a similar ruthenium complex, RuCl2(PPh3)3, which had not been reported before as a Michael additions catalyst. Faced with these results we decided to to take advantage of the excellent catalytic activity of RuCl2(PPh3)3 to widden this study to several non-chiral b-dicarbonyl compounds. Further studies so that try to establish the reaction mechanism were undertaken. In the course of this study we observed the lack of catalytic activity of Ru species lacking phosphine ligands (e.g. CpRu(N*C-CH3)3PF6). On the other hand, PPh3 showed to be a good catalyst for Michael additions even when working under conditions under which both RuCl2(PPh3)3 and RuH2(PPh3)4 showed no catalytic activity at all. This results led us to conclude that the responsible for the catalysis of the Michael additions which underwent in the presence of RuCl2(PPh3)3 or RuH2(PPh3)4 was not a Ru specie, but the PPh3. We have postulated mechanistic hypothesis for the Michael additions catalyzed by triphenylphosphine. In this mechanism the triphenylphosphine initiates the process by reacting with the electron-deficient olefin in a reminiscent way of Baylis-Hillman reaction, or Mitsunobu reaction when the electrophile is a dialkyl azodicarboxylate. In the second chapter of this doctoral thesis, we developed an study of perfluoroalkylation of olefins. Once again, the triphenylphosphine showed high catalytic activity in the putative catalysis by RuCl2(PPh3)3 in the perfluoroalkylation of olefins. The triphenylphosphine catalyzed eficiently the addition of perfluorooctyl iodide to several both linear and cyclic alkenes. We proposed as a mechanism for this reactions a single electron transfer radical chain process. The inhibition of the reaction by a radical scavenger addition, as well as the lack of reactivity of some olefins which led to the formation of stabilized radicals, constitute some evidences of the radical nature of the process

Establishment and Expansion of harmonia axyridis Pallas (Coleoptera: Coccinellidae) in urban green areas in the Iberian Peninsula: from 2015 to 2021

Harmonia axyridis (Coleoptera: Coccinellidae) is a widespread invasive ladybird. In this study, we determine its occurrence and expansion in urban areas of the Iberian Peninsula after 2014. We also define the aphidophagous ladybird species complex in urban areas of the northeastern Iberian Peninsula and track any changes between 2015 and 2021. The expansion of the species mainly occurred in Catalonia (northeast Iberian Peninsula), where spring and summer populations on trees and shrubs and overwintering aggregations were recorded. The records of H. axyridis populations allow us to distinguish between two areas: one that has already been invaded and another that has not yet been invaded. The relative abundance of the ladybird species in each area is determined on a yearly basis. In the invaded area, H. axyridis became dominant two years after its detection, replacing Adalia bipunctata. This change in species prevalence is more pronounced in trees highly infested with aphids. In the not yet invaded area, changes in species dominance also occurred, and A. bipunctata replaced Oenopia conglobata from 2020 onwards. The yearly release of this ladybird in urban green areas for aphid control purposes could explain this shift. This study defines the current situation of H. axyridis in the Iberian Peninsula, and determines the main changes in ladybird species assemblages during the last few years

Characterization of a newly established aggregation of the invasive ladybeetle Harmonia axyridis and current status of the invader in Spain

The multicoloured Asian ladybeetle, Harmonia axyridis (Pallas), an invasive biocontrol agent introduced in North and South America, as well as in Europe for aphid control, drastically affected assemblages of native coccinellid species, local communities and people. Although the insect is common in several European countries and it was released in Spain for aphid control in 1995, no evidence of population establishment has been reported until 2011. In the present paper, 1) we summarize the records of the invasive ladybeetle in Spain and provide numerous new mentions, and 2) we follow for the first time an overwintering aggregation from autumn to spring and characterize some individual features which allow us to determine its phenology of the establishment and spreading. The results establish clearly that: 1) H. axyridis is (until now) restricted to Catalonia (NE Spain) but the invading process is in progress and the insect is able to occupy different habitats; 2) the ladybeetle overwinters successfully in Spain without significant natural mortality or parasitism; 3) the form succinea represents 73-81% of the overwintering individuals, and 4) the invasion takes probably its origin from Southern France. The potential impact of the invasion by H. axyridis in Spain is discussed

Expansión de Lysiphlebus testaceipes (Cresson) (Hym., Braconidae, Aphidiinae) en el Noreste de la Península Ibérica

Lysyphlebus testaceipes (Cresson), un parasitoide exótico de pulgones establecido en la costa mediterránea, se ha encontrado regularmente en Lleida y en los Pirineos parasitando varias especies de pulgones, lo que demuestra su expansión desde las zonas costeras hacia el interior y zonas de montaña. Las especies de pulgón Aphis ruborum Börner, específica de Rubus sp., Aphis fabae Scopoli, polífaga, Brachycaudus cardui L., típica de cardos y Aphis urticata J.F. Gmelin, específica de Urtica sp., fueron hospedantes comunes de L. testaceipes en las zonas de estudio. La existencia de biocorredores transzonales, junto con el rango oligófago de hospedantes de L. testaceipes y su capacidad de alternar entre las especies de pulgones disponibles ha contribuido a la positiva expansión del parasitoide hacia zonas interiores o de montaña.Lysiphlebus testaceipes (Cresson), an exotic aphid parasitoid established in the Mediterranean coast, has been regularly found in Lleida, and in the Pyrenees parasitising several aphid species. This shows the expansion of the parasitoid from coastal areas to the inland and mountain areas. The aphid species Aphis ruborum Bõrner, specific of Rubus sp., the polyphagous Aphis fabae Scopoli, Brachycaudus cardui L., and Aphis urticata J.F. Gmelin, specific of Urtica sp., were usual host of L. testaceipes in the studied areas. The presence of transzonal biocorridors, joint to the oligophagous host range of L. testaceipes and its capacity to alternate between available host aphid species has contributed to the successful expansion of the parasitoid from the coast to the inland or mountain areas

Representative taxa in field trials for environmental risk assessment of genetically modified maize

When assessing the benefits and risks of transgenic crops, one consideration is their relative effects on non-target arthropod (NTA) abundance and functions within agroecosystems. Several laboratory and field trials have been conducted in Spain since the late 1990s to assess this issue. A consideration in the design of field trials is whether it is necessary to sample most NTAs living in the crop or only representative taxa that perform main ecological functions and have a good capacity to detect small changes in their abundance. Small changes in the field abundance of an effective representative taxon should be detectable using standard experimental protocols. The ability of a species to reveal differences across treatments may be analysed by examining the detectable treatment effects for surveyed non-target organisms. Analysis of data from several NTAs recorded in 14 field trials conducted over 10 years using complete block designs allowed us to select a number of representative taxa capable of detecting changes in the density or activity of arthropod herbivores, predators, parasitoids and decomposers in transgenic and non-transgenic maize varieties. The most suitable NTA as representative taxa (with detectable treatment effects below 50%) included leafhoppers among arthropod herbivores, Orius spp., Araneae, and Carabidae among predators, chalcidids, particularly the family Mymaridae, among parasitoids and Chloropidae as decomposer. Details of sampling techniques for each sampled taxa and their advantages and disadvantages are discussed. It is concluded that abundance of taxa is the most influential factor determining their capacity to detect changes caused by genetically modified varieties.Peer ReviewedPostprint (published version

Optimal Supply Chain Strategy through Stochastic Programming

In this project, a new two-stage stochastic programming decision model has been developed to assess: (a) the convenience of introducing 3D printing into any generic manufacturing process, both single and multi-product; and (b) the optimal degree of postponement known as the customer order decoupling point (CODP) while also assuming uncertainty in demand for multiple markets. To this end, we propose the formulation of a generic supply chain through an oriented graph that represents all the deployable alternative technologies. These are defined through a set of operations for manufacturing, assembly and distribution, each of which is characterized by a lead time and cost parameters. Based on this graph, we develop a mixed integer two-stage stochastic program that finds the optimal manufacturing technology to meet the demand of each market, the optimal production quantity for each operation, and the optimal CODP for each technology. The results obtained from several case studies in real manufacturing companies are presented and analyzed. The work presented in this master s thesis is part of an ongoing research project between UPC and Accenture