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

Translating habitat class to land cover to map area of habitat of terrestrial vertebrates.

Area of habitat (AOH) is defined as the "habitat available to a species, that is, habitat within its range" and is calculated by subtracting areas of unsuitable land cover and elevation from the range. The International Union for the Conservation of Nature (IUCN) Habitats Classification Scheme provides information on species habitat associations, and typically unvalidated expert opinion is used to match habitat to land-cover classes, which generates a source of uncertainty in AOH maps. We developed a data-driven method to translate IUCN habitat classes to land cover based on point locality data for 6986 species of terrestrial mammals, birds, amphibians, and reptiles. We extracted the land-cover class at each point locality and matched it to the IUCN habitat class or classes assigned to each species occurring there. Then, we modeled each land-cover class as a function of IUCN habitat with (SSG, using) logistic regression models. The resulting odds ratios were used to assess the strength of the association between each habitat and land-cover class. We then compared the performance of our data-driven model with those from a published translation table based on expert knowledge. We calculated the association between habitat classes and land-cover classes as a continuous variable, but to map AOH as binary presence or absence, it was necessary to apply a threshold of association. This threshold can be chosen by the user according to the required balance between omission and commission errors. Some habitats (e.g., forest and desert) were assigned to land-cover classes with more confidence than others (e.g., wetlands and artificial). The data-driven translation model and expert knowledge performed equally well, but the model provided greater standardization, objectivity, and repeatability. Furthermore, our approach allowed greater flexibility in the use of the results and uncertainty to be quantified. Our model can be modified for regional examinations and different taxonomic groups

Drivers of habitat availability for terrestrial mammals: Unravelling the role of livestock, land conversion and intrinsic traits in the past 50 years

The global decline of terrestrial species is largely due to the degradation, loss and fragmentation of their habitats. The conversion of natural ecosystems for cropland, rangeland, forest products and human infrastructure are the primary causes of habitat deterioration. Due to the paucity of data on the past distribution of species and the scarcity of fine-scale habitat conversion maps, however, accurate assessment of the recent effects of habitat degradation, loss and fragmentation on the range of mammals has been near impossible. We aim to assess the proportions of available habitat within the lost and retained parts of mammals' distribution ranges, and to identify the drivers of habitat availability. We produced distribution maps for 475 terrestrial mammals for the range they occupied 50 years ago and compared them to current range maps. We then calculated the differences in the percentage of 'area of habitat' (habitat available to a species within its range) between the lost and retained range areas. Finally, we ran generalized linear mixed models to identify which variables were more influential in determining habitat availability in the lost and retained parts of the distribution ranges. We found that 59% of species had a lower proportion of available habitat in the lost range compared to the retained range, thus hypothesizing that habitat loss could have contributed to range declines. The most important factors negatively affecting habitat availability were the conversion of land to rangeland and high density of livestock. Significant intrinsic traits were those related to reproductive timing and output, habitat breadth and medium body size. Our findings emphasize the importance of implementing conservation strategies to mitigate the impacts caused by human activities on the habitats of mammals, and offer evidence indicating which species have the potential to reoccupy portions of their former range if other threats cease to occur.This study investigates the impact of habitat degradation on terrestrial mammal species. By comparing historic and current distribution maps for 475 species, we found that 59% of them have less available habitat in their lost ranges, suggesting habitat loss contributed to range declines. Factors like land conversion to rangeland and high livestock density negatively affected habitat availability. Intrinsic traits such as reproductive timing, habitat breadth and medium body size also played a role. The study underscores the need for conservation efforts to mitigate human-induced habitat threats and identifies species that could potentially reclaim lost range if threats are addressed.imag

Where will further Key Biodiversity Areas be identified? A modeling approach to focus efforts

Life on Earth is facing a sixth mass extinction, and the main driver of biodiversity loss is habitat destruction. Area-based conservation has been proven vital in preventing species extinction and protecting habitats. However, the current network is not ecologically representative, diminishing the potential role of area-based conservation in reducing biodiversity loss. In this context, identifying new Key Biodiversity Areas (KBAs) is essential. KBAs are defined as 'sites contributing significantly to the global persistence of biodiversity'. Although the KBAs approach is built on previous site-based conservation methodologies, the KBAs identification process still has some challenges to overcome. With this PhD, I aimed to standardize, improve and facilitate the KBAs identification process providing accurate and available biodiversity data for the identification of KBAs and contributing to the KBAs Guidelines for Criterion E, irreplaceability through quantitative analysis. Area of Habitat (AOH) stands out as a crucial assessment parameter to identify KBAs because it generally reduces the risk of commission error of range maps and is more available than other assessment parameters such as Area of Occupancy (AOO) or the number of mature individuals. AOH is 'the habitat available to a species, that is, habitat within its range'. The production of AOH maps requires an understanding of which habitats a species occurs in. Habitat associations are documented using the IUCN Habitats Classification Scheme. Unvalidated expert opinion is typically used to match habitat to land-cover classes, generating a source of uncertainty in AOH maps. In the first research chapter, Translating habitat classes to land cover to map Area of Habitat for terrestrial vertebrates, I developed a standardised, data-driven methodology to translate IUCN habitat classes into two land-cover maps using point locality data for mammals, birds, amphibians, and reptiles. I generated two translation tables, quantifying the strength of association between habitat and land-cover classes using the odd ratio values of logistic regression models. I calculated the association between habitat and land-cover classes as a continuous variable. However, to map AOH as binary presence or absence, it was necessary to apply an association threshold that can be chosen by the user according to the required balance between omission and commission errors. The data-driven translation provided greater standardisation, objectivity, and repeatability, and the model can be modified for regional examinations and different taxonomic groups. In the second research chapter, Mapping Area of Habitat for the world's terrestrial birds and mammals, I produced an updated version of global AOH maps 5,481 terrestrial mammals and 10,651 terrestrial bird species. For 1,816 bird species defined by BirdLife International as migratory, I developed three AOH maps, one for the resident range, one for the breeding range and one for the non-breeding range. The maps have a resolution of 100 m. On average, AOH covered 66±28% of the range maps for mammals and 64±27% for birds. I used AOH maps to produce global maps of the species richness of mammals, birds, globally threatened mammals and globally threatened birds. These maps represent an increase in resolution compared with species richness maps produced using the IUCN range maps, helping to identify biodiversity hotspots accurately. Having clear and standardised guidelines to identify KBAs is as crucial for identifying KBAs as having the most accurate high-quality data. The KBAs identification process requires all users to apply the KBAs Standard consistently. However, for KBAs Criterion E, the guidelines are still incomplete as methods are still in development. Sites qualify as Key Biodiversity Areas (KBAs) under KBAs Criterion E if they have a very high irreplaceability value (>0.9 on a 0-1 scale) derived from a quantitative spatial prioritisation analysis. The irreplaceability of a site is determined by both the biodiversity found within it and the biodiversity contained in the other sites considered in the analysis. In the third research chapter, Evaluating Irreplaceability in KBAs and the effects of the geographical scale, I explored the identification of KBAs based on Criterion E in two geographical regions, South America and East Africa, for terrestrial mammals. In the South American analysis, I found that, on average, 47% of regionally irreplaceable planning units were not represented in country-level analyses, while country-level analyses mainly represented a subset of the regional ones. These results indicated that at the regional level, irreplaceability was driven by endemic species and species richness, while at the country level, exclusively by endemic species. For some African counties, the analysis produced very few or no highly-irreplaceable planning units. This could indicate that the current targets were too low for these countries. I concluded that the results obtained from the current formulation of Criterion E are affected by the geographical scale and region in which it is applied. The KBAs Standards and Appeals Committee could take some actions to make the analysis more robust, such as setting the scale of application at the regional level and revising the targets. I expect that the research carried out in this PhD constitutes an advance of the current knowledge on KBAs and serve as a starting point for future developments

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

Una 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

Important first steps towards designing the freshwater, marine and terrestrial Essential Biodiversity Variable (EBV) workflows for the European Biodiversity Observation Network

The EuropaBON project aims to co-design a European Biodiversity Observation Network by utilising Essential Biodiversity Variables (EBVs) as the foundation for its monitoring system. To co-design the workflow steps for each EBV, the project organised a virtual workshop to engage a diverse group of experts and stakeholders. The workshop focused on describing various workflow components, identifying future needs for EBV implementation and specifying the relative importance of different monitoring techniques for each EBV. With 520 participants from 49 countries, the workshop benefited from a large stakeholder engagement and a wide range of expertise across realms, EBV classes, monitoring techniques and workflow components. During the 3-day workshop (2 hours per day), participants captured different workflows components (i.e. data collection and sampling, data integration and modelling), specified current EU or national initiatives and identified emerging tools and future needs for all 70 currently proposed EBVs. By the end of the workshop, all 70 templates of EBV workflows contained details about workflow components and future needs. Specific future needs for data collection and sampling highlighted by participants were to increase sampling efforts (e.g. number of sites, geographic coverage, sampling frequency and taxonomic scope), to develop and better incorporate novel monitoring techniques (e.g. eDNA, remote sensing and digital sensors) and to create new or improved sampling designs at a European scale. For data integration, combining and harmonising data from diverse sources and data collectors and developing standards and protocols were mentioned as key needs. For modelling, participants especially highlighted the need to develop spatially-explicit models or improve other types of existing models, ideally with open-source software and code. Next steps for designing EBV workflows are to analyse the gathered workshop information, to provide detailed descriptions of EBV workflows and to formulate specific recommendations for the development of a European Biodiversity Observation Network. Recommendations for each monitoring technique (structured in-situ monitoring, citizen science, digital sensors, genetics, satellite remote sensing and aerial remote setting) will also be identified. The gathered information will contribute to the co-design of the European Biodiversity Observation Network and to supporting the establishment of a Biodiversity Monitoring Coordination Centre in Europe

Essential Biodiversity Variable workflows: designing the freshwater, marine and terrestrial EBV workflows from data collection to modeling

This document will form the basis for the EuropaBON virtual workshop on EBV workflows (22-24 February 2023) and for developing the co-design of the European Biodiversity Observation Network

Maps of area of habitat for Italian amphibians and reptiles

Planning conservation actions requires detailed information on species’ geographic distribution. Species distribution data are most needed in areas hosting unique or endangered biodiversity. Italy is one of the European countries with the highest levels of herpetological diversity and endemism and is home to several threatened species of amphibians and reptiles. Information on the distribution of species’ habitats can help identify sites where the species is most likely to thrive, as viable populations depend on it. Area of Habitat (AOH) maps reveal the distribution of the habitat available to the species within their geographic range. We produced high resolution, freely accessible global area of habitat maps for 60 species of reptiles and amphibians distributed in Italy, which represent 60% of all Italian amphibian and reptile species. We validated a total of 44 AOH maps through a presence-only based evaluation method, with 86% of these maps showing a performance better than expected by chance. AOH maps can be used as a reference for conservation planning, as well as to investigate macroecological patterns of Italian herpetofauna. Furthermore, AOH maps can help monitoring habitat loss, which is known to be a major threat to many reptile and amphibian species in Europe