The synthesis of aromatic amines is of utmost importance in a wide range of chemical contexts. We report a direct amination of boronic acids with nitro compounds to yield (hetero)aryl amines. The ...novel combination of a dioxomolybdenum(VI) catalyst and triphenylphosphine as inexpensive reductant has revealed to be decisive to achieve this new C−N coupling. Our methodology has proven to be scalable, air and moisture tolerant, highly chemoselective and engages both aliphatic and aromatic nitro compounds. Moreover, this general and step‐economical synthesis of aromatic secondary amines showcases orthogonality to other aromatic amine syntheses as it tolerates aryl halides and carbonyl compounds.
C−N coupling: A new electrophilic amination of boronic acids with simple and inexpensive nitro compounds has been developed allowing the preparation of a variety of highly substituted and functionalized aromatic secondary amines. The process employs affordable PPh3 as reducing agent, in the presence of an easily available and highly stable dioxomolybdenum(VI) complex as catalyst.
Bryophytes have been proposed as ideal indicators of ecosystem change, because they are important components of forest integrity, and considerable research indicates that some groups are sensitive to ...the changes associated with specific human disturbances. Bryophyte richness and abundance have been found to vary predictably along elevational gradients, but the role of human impacts on these distribution patterns remains unclear. The aim of this study is to explore the impact of human disturbance on the elevational patterns of bryophyte diversity, along an elevational gradient. Along the gradient we collected three datasets in the following sites: preserved (P), forest track roadsides (R) and disturbed by agriculture/silviculture practices (D). Two survey plots of 100 m2 were established at every 200 m elevational step for each sites P, R, D, and in each plot bryophytes were sampled in a stratified manner. At each plot we recorded all species on available substrates and estimated their percentage cover. Our results showed that species number did not differ among studied sites, but that species diversity pattern differs among the three gradient types and species life strategy composition along the elevational gradient showed a clear response to the disturbance of mature communities. We conclude that human impact has strongly changed the elevational pattern of diversity, and that these changes vary depending on the ecological and taxonomical group considered.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
In recent years, the study of women entrepreneurship has experienced great growth, gaining a broad consensus among academics and contributing above all to understanding all those factors that explain ...the difficulty of women in undertaking an entrepreneurial career. This document tries to contribute to the field of study, thanks to a systematic analysis through the publications present in the topic. For this purpose, 2,848 peer-reviewed articles were analyzed, published between 1950 and 2019, using the Scopus database (SCImago Research Group). Through the use of a series of bibliometric indicators it was possible to define the current state of research on the international scene. The analysis revealed that it is a multidisciplinary field of study and that has started to expand further since 2006, culminating in 2019, which makes it become a current and valid object of study. The analysis of the clusters allowed to isolate 6 different lines of research in which emerged, on the one hand, the importance of entrepreneurial education, social entrepreneurship and the socio-cultural context of reference (e.g., culture, family, and institutional support) as tools to overcome the gender gap, on the other, the importance that women entrepreneurship assumes in the economic growth of the country (especially in developing economies), promoting social inclusion and combating poverty and discrimination. The study presents an important contribution to reflect on current policies and to outline future lines of investigation.
In recent years, honeybees (Apis mellifera) have been strangely disappearing from their hives, and strong colonies have suddenly become weak and died. The precise aetiology underlying the ...disappearance of the bees remains a mystery. However, during the same period, Nosema ceranae, a microsporidium of the Asian bee Apis cerana, seems to have colonized A. mellifera, and it's now frequently detected all over the world in both healthy and weak honeybee colonies. For first time, we show that natural N. ceranae infection can cause the sudden collapse of bee colonies, establishing a direct correlation between N. ceranae infection and the death of honeybee colonies under field conditions. Signs of colony weakness were not evident until the queen could no longer replace the loss of the infected bees. The long asymptomatic incubation period can explain the absence of evident symptoms prior to colony collapse. Furthermore, our results demonstrate that healthy colonies near to an infected one can also become infected, and that N. ceranae infection can be controlled with a specific antibiotic, fumagillin. Moreover, the administration of 120 mg of fumagillin has proven to eliminate the infection, but it cannot avoid reinfection after 6 months. We provide Koch's postulates between N. ceranae infection and a syndrome with a long incubation period involving continuous death of adult bees, non-stop brood rearing by the bees and colony loss in winter or early spring despite the presence of sufficient remaining pollen and honey.
Abstract We report the efficient, sustainable one‐pot synthesis of a wide variety of N ‐polyheterocycles, such as imidazo‐quinolines and quinoxalines, and furoquinolines, from easily available ...nitroaromatics and glycols via a molybdenum catalytic domino reduction‐imine formation‐intramolecular cyclization‐oxidation sequence. It is worth highlighting that the recycling and incorporation of the waste carbonyl byproduct, generated in the reduction step, into the final compound is realized. In addition, the overall efficiency and atom economy of the process are further improved owing to the participation of one reaction intermediate as reductant that allows lowering the amount of external reducing agent employed.
A catalytic domino reduction–imine formation–intramolecular cyclization–oxidation for the general synthesis of a wide variety of biologically relevant N‐polyheterocycles, such as quinoxaline‐ and ...quinoline‐fused derivatives, and phenanthridines, is reported. A simple, easily available, and environmentally friendly dioxomolybdenum(VI) complex has proven to be a highly efficient and versatile catalyst for transforming a broad range of starting nitroarenes involving several redox processes. Not only is this a sustainable, step‐economical as well as air‐ and moisture‐tolerant method, but also it is worth highlighting that the waste byproduct generated in the first step of the sequence is recycled and incorporated in the final target molecule, improving the overall synthetic efficiency. Moreover, selected indoloquinoxalines have been photophysically characterized in cyclohexane and toluene with exceptional fluorescence quantum yields above 0.7 for the alkyl derivatives.
A catalytic domino reduction / imine formation / intramolecular cyclization / oxidation allows the synthesis of a wide variety of biologically relevant N‐polyheterocycles. The reported process employs an inexpensive and nontoxic dioxomolybdenum(VI) complex as catalyst, easily available nitroarenes as starting materials and different glycols as reducing agents with reuse of the waste reduction carbonyl byproduct, which is embodied into the final compounds.
Evolutionary multiobjective optimization has been a research area since the mid-1980s, and has experienced a very significant activity in the last 20 years. However, and in spite of the maturity of ...this field, there are still several important challenges lying ahead. This paper provides a short description of some of them, with a particular focus on open research areas, rather than on specific research topics or problems. The main aim of this paper is to motivate researchers and students to develop research in these areas, as this will contribute to maintaining this discipline active during the next few years.
Questions: We addressed three questions: (1) what is the variation of α- and β-diversity of bryophyte communities across spatial scales in an elevational gradient; (2) is spatial variation ...characteristic of different phylogenetic (mosses/liverworts) and/or ecological groups (terrestrials/epiphytes); and (3) what is the contribution of species richness and species replacement (true turnover) to β-diversity along the elevational gradient? Location: La Palma, Canary Islands, Spain. Methods: An elevational transect spanning 0–2200 m a.s.l was sampled at altitudinal intervals of ca. 200 m, two 10 m × 10 m plots were established at each elevation and inside each plot three 2 m × 2 m quadrats were randomly selected. Within each quadrat, bryophytes were sampled in three replicate microplots of 10 cm × 5 cm, for each substrate: soil, rocks, leaves, humus, decaying wood and tree trunks at three heights. We evaluated α- and β-diversity at plot and elevational level for all bryophytes and for phylogenetic and ecological groups. Values of β-diversity were further decomposed into replacement and richness differences. We tested the relationship between α- and β-diversity and elevation using linear models with and without a quadratic term (elevation2) in an AICc-based framework. Results: A total of 121 species were recorded along the transect. Alpha-diversity showed a hump-shaped pattern with elevation for all bryophytes, liverworts and epiphytic species, however, terrestrial species and mosses displayed no clear pattern. Species replacement was the main driver of β-diversity for all bryophytes and also for mosses and terrestrial species, and at different scales (elevational belt and quadrat). The contribution of species replacement increased with elevation, except for epiphytes and terrestrials. Conclusions: Our study contributes towards an understanding of the spatial organization of bryophyte diversity at different scales along an insular elevational gradient. We showed that bryophyte diversity was mostly influenced by species replacement at the largest scale. The observed differences in β-diversity decomposition between bryophyte phylogenetic and ecological groups could be dependent on climatic conditions and substrate availability. The strong differences observed along the elevational gradient related to true turnover are especially important in the current global change scenario.
In non-fire prone ecosystems, like some subtropical humid forests, fire produces habitat destruction and intensifies land degradation by inducing changes in native species composition, soil ...properties and erosive processes. Bryophytes are key components of the Macaronesian laurel forests playing an important role in regulating water cycling and microclimate. Ecological and taxonomical bryophytes groups have distinct ecological and physiological requirements and may respond in a different way to the same fire events. Therefore, analysing post fire recovery of bryophyte communities represents a key step towards a better understanding of forest fire drivers and post fire management. We investigated how species richness and composition of different ecological and taxonomical bryophyte groups varied in 1158 samples within a fire chronosequence from 5 to 57 years in the best-preserved laurel forest from Canary Islands (Garajonay National Park) analysing communities in terms of differences with comparable surrounding old growth unburnt stands. Epiphyte, terricolous and saxicolous bryophytes were sampled at each plot and the influence of the time since fire was analyzed together with environmental variables (temperature, precipitation, mist precipitation and elevation) and forest structure variables. Our results indicate that there is no general pattern of post fire recolonization, as recolonization varies depending on the ecological and phylogenetic groups considered. Climate and forest structure play an important role in post-fire recolonization, such that time since fire is not the most important variable influencing richness and composition. The results increase the understanding of the processes that shape compositional patterns in groups with high dispersal capacities and high microclimate dependence, such as mosses and liverworts.
•Bryophytes are evaluated here as potential bioindicators of heterogeneous fire effects in non-fire prone subtropical cloud forests.•There is no general post-fire recolonization pattern by bryophytes and the effects vary depending on the ecological and phylogenetic studied group.•Climate and forest structure play an essential role in post-fire recolonization.•Time since fire is not the most important driver influencing abundance and composition in bryophytes.•There is a notable influence of colonization from the surrounding non-burnt forests and the distance to the dispersal source.
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