Synthesis of Chroman-2,4-diones via Ring-Opening/Ring-Closing Reaction Involving Palladium-Catalyzed Intramolecular Aryloxycarbonylation.

Palladium-catalyzed aminocarbonylation of 3-iodochromone was studied in the presence of primary and secondary amines using atmospheric pressure of carbon monoxide as a carbonyl source. This procedure successfully provided a library of chromone-3-carboxamides and 3-substituted chroman-2,4-diones in 40 to 92% isolated yields. The reaction proceeded via highly chemoselective aminocarbonylation (up to 100%) in the presence of secondary amines by using monodentate or bidentate phosphine ligands. The tendency of 3-iodochromone substrate to undergo ANRORC rearrangement with N-nucleophiles was crucial to shift the reaction toward an unprecedented chemoselective carbonylative transformation, where a late-stage carbonyl insertion is favored concomitantly to the last ring-closure step. The proposed aza-Michael addition/ring-opening/intramolecular aryloxycarbonylation sequence showed compatibility, uniquely, to primary amines when XantPhos was used as a ligand. The solid-state structures of chromone-3-carboxamide (2a) and chroman-2,4-dione (3s) were undoubtedly established by single-crystal XRD analysis. A catalytic cycle was proposed to rationalize the formation of the two types of carbonylated compounds.

PADAPT 1.0 - the Pannonian Dataset of Plant Traits.

The existing plant trait databases' applicability is limited for studies dealing with the flora and vegetation of the eastern and central part of Europe and for large-scale comparisons across regions, mostly because their geographical data coverage is limited and they incorporate records from several different sources, often from regions with markedly different climatic conditions. These problems motivated the compilation of a regional dataset for the flora of the Pannonian region (Eastern Central Europe). PADAPT, the Pannonian Dataset of Plant Traits relies on regional data sources and collates data on 54 traits and attributes of the plant species of the Pannonian region. The current version covers approximately 90% of the species of the region and consists of 126,337 records on 2745 taxa. By including species of the eastern part of Europe not covered by other databases, PADAPT can facilitate studying the flora and vegetation of the eastern part of the continent. Although data coverage is far from complete, PADAPT meets the longstanding need for a regional database of the Pannonian flora.

New thousand-seed weight dataset for plant species of Central Europe.

One of the most important and most easily measurable physical characteristics of plant seeds is their weight, which influences and indicates crucial ecological processes. Seed weight affects spatial and temporal dispersibility, and can also influence seed predation and the germination, growth and survival of seedlings. Providing trait data for species missing from international databases is key to promote studies that advance our understanding of the functioning of plant communities and ecosystems, which is an essential issue in the face of the global climate change and biodiversity loss. Compared to species from Western and Northwestern Europe, those with an Eastern or Central European centre of distribution are underrepresented in most international trait databases. Therefore, the creation of specific trait databases is key to help regional studies. In this respect, it is important not only to collect fresh seeds for weight measurements, but also to measure and process data of seeds preserved in collections and make them available to the broader scientific community. In this data paper we provide seed weight data to fill in missing trait data of plant species of Central and Eastern Europe. Our dataset includes weight measurement for 281 taxa of the Central European flora including also some cultivated and exotic species. The seeds were collected between 1971 and 2021 mostly in Central Europe. One part of the measured seeds was collected in the last decade, the other part is from an older seed collection, but all seeds were measured recently. For each species, we collected a minimum of 3 × 100 intact seeds, if possible. The seeds were air-dried at room temperature (approximately 21 °C and 50% relative humidity) for at least two weeks and measured with an accuracy of 0.001 g using an analytical balance. The thousand-seed weights reported here were calculated based on the measured values. Our goal for the future is to incorporate the seed weight data reported here in a regional database (Pannonian Database of Plant Traits - PADAPT) that gathers plant traits and other plant characteristics for the Pannonian flora. The data presented here will facilitate trait-based analyses of the flora and vegetation of Central Europe.

Palladium-Catalyzed Selective Amino- and Alkoxycarbonylation of Iodoarenes with Aliphatic Aminoalcohols as Heterobifunctional O,N-Nucleophiles.

Palladium-catalyzed amino- and alkoxycarbonylation reactions of aryl iodides were investigated in the presence of aliphatic heterobifunctional N,O-nucleophiles. Selective synthesis of amide alcohols and amide esters was realized, controlled by the base and substrate ratio. The effect of iodobenzene substituents was also studied with surprising results in terms of product selectivity. In addition to the model ethanolamine/iodobenzene system, various heteroaromatic substrates and numerous related nucleophiles were tested under optimized conditions, providing moderate to good yields of the target compounds. Reactions of serinol and 1,3-diamino-2-propanol as model trifunctional compounds showed particularly high chemoselectivity on amide ester products. Considering the coordinative properties of the applied nucleophiles, a rational catalytic cycle was proposed.

Alkyl Levulinates and 2-Methyltetrahydrofuran: Possible Biomass-Based Solvents in Palladium-Catalyzed Aminocarbonylation.

In this research, ethyl levulinate, methyl levulinate, and 2-methyltetrahydrofuran as bio-derived hemicellulose-based solvents were applied as green alternatives in palladium-catalyzed aminocarbonylation reactions. Iodobenzene and morpholine were used in optimization reactions under different conditions, such as temperatures, pressures, and ligands. It was shown that the XantPhos ligand had a great influence on conversion (98%) and chemoselectivity (100% carboxamide), compared with the monodentate PPh3. Following this study, the optimized conditions were used to extend the scope of substrates with nineteen candidates (various para-, ortho-, and meta-substituted iodobenzene derivatives and iodo-heteroarenes), as well as eight different amine nucleophiles.

New data of plant leaf traits from Central Europe.

Trait-based ecology is gaining ground nowadays on species-based ecology: the number of research and publication focusing on the ecological role of taxa instead of the species themselves increased significantly in the last two decades. One great advantage of this approach is that communities with different species composition due to great geographical distances (e.g., different continents) or different environmental conditions (e.g., loess, sand, and alkaline grasslands) become comparable. Obtaining trait values is, however, labour and time consuming even in the case of so-called soft traits. It is therefore reasonable and desirable for scientists to share their data as widely as possible. Demand for such data induced the publication of data papers and the establishment of databases, which support both theoretical ecological research and practical restoration ecological projects. Although several international databases (e.g., TRY, LEDA, CLO-PLA, BiolFLOR) are available nowadays, Central and Eastern European species are either missing or underrepresented in them. Consequently, measurement and publication of the traits of species typical in the above region is necessary. This paper presents leaf trait (leaf fresh and dry weight, leaf area, specific leaf area and leaf dry matter content) data for more than 1100 species of the Central European flora.

Trade of commercial potting substrates: A largely overlooked means of the long-distance dispersal of plants.

Although long-distance dispersal (LDD) events are rare and stochastic, they are disproportionately important and drive several large-scale ecological processes; yet, we have a very limited understanding of their frequency, extent and consequences. Humanity intentionally spreads several species, which is associated with the accidental dispersal of other plant species. Although the global trade of potted plants and horticultural substrates may disperse large quantities of propagules, it has hardly been studied from an ecological point of view. We assessed the viable seed content of different types of commercial potting substrates to answer the following questions: (i) In what richness and density do substrates contain viable seeds? (ii) Does the composition of substrates influence their viable seed content? and (iii) Are there common characteristics of the species dispersed this way? We detected 438 seedlings of 66 taxa and found that 1 l of potting substrate contains an average of 13.27 seeds of 6.24 species, so an average 20-liter bag of substrate contains 265 viable seeds. There was a high variability in the seed content of the substrates, as substrates containing manure contained a substantially higher number of species and seeds than substrates without manure. Thus, this pathway of LDD is an interplay between endozoochory by grazing livestock and accidental human-vectored dispersal, implying that the diet preference of grazing animals influences the ability of a plant species to be dispersed this way. According to our results, potting substrates can disperse large quantities of seeds of a wide range of plant species over large distances. We conclude that this kind of human-vectored LDD may have complex effects on plant populations and communities; however, as this dispersal pathway is largely understudied and has hardly been considered as a type of LDD, its consequences are still unknown and further studies of the issue are of great importance.

Selective Synthesis of N-Acylnortropane Derivatives in Palladium-Catalysed Aminocarbonylation.

The aminocarbonylation of various alkenyl and (hetero)aryl iodides was carried out using tropane-based amines of biological importance, such as 8-azabicyclo[3.2.1]octan-3-one (nortropinone) and 3α-hydroxy-8-azabicyclo[3.2.1]octane (nortropine) as N-nucleophile. Using iodoalkenes, the two nucleophiles were selectively converted to the corresponding amide in the presence of Pd(OAc)2/2 PPh3 catalysts. In the presence of several iodo(hetero)arenes, the application of the bidentate Xantphos was necessary to produce the target compounds selectively. The new carboxamides of varied structure, formed in palladium-catalyzed aminocarbonylation reactions, were isolated and fully characterized. In this way, a novel synthetic method has been developed for the producing of N-acylnortropane derivatives of biological importance.

Highly Selective Synthesis of 6-Glyoxylamidoquinoline Derivatives via Palladium-Catalyzed Aminocarbonylation.

The aminocarbonylation of 6-iodoquinoline has been investigated in the presence of large series of amine nucleophiles, providing an efficient synthetic route for producing various quinoline-6-carboxamide and quinoline-6-glyoxylamide derivatives. It was shown, after detailed optimization study, that the formation of amides and ketoamides is strongly influenced by the reaction conditions. Performing the reactions at 40 bar of carbon monoxide pressure in the presence of Pd(OAc)2/2 PPh3, the corresponding 2-ketocarboxamides were formed as major products (up to 63%). When the monodentate triphenylphosphine was replaced by the bidentate XantPhos, the quinoline-6-carboxamide derivatives were synthesized almost exclusively under atmospheric conditions (up to 98%). The isolation and characterization of the new carbonylated products of various structures were also accomplished. Furthermore, the structure of three new mono- and double-carbonylated compounds were unambiguously established by using a single-crystal XRD study.

The protected flora of long-established cemeteries in Hungary: Using historical maps in biodiversity conservation.

The role of anthropogenically influenced habitats in conserving elements of the original wildlife has increased worldwide simultaneously with the disappearance of natural sites. Burial places are able to conserve original elements of the wildlife, and this fact has been known for at least a century. To this day, little is known about long-time changes and the effect of long-time management methods in cemeteries on the flora they harbor. The utility of historical maps in research focused on natural values, as well as in answering questions related to conservation was recently demonstrated, but the use of digitized historical maps in biodiversity research of the Carpathian Basin is very limited. In the present paper, we aimed to predict the conservation potential of long-established and newly established cemeteries of Hungarian settlements with various population sizes based on the digitized maps of the 2nd Military Survey of the Austrian Empire (1819-1869), by categorizing cemeteries into 3 distinct (anthropogenic habitat, cemetery, or natural habitat) types. To build our models, we used records of the protected flora from Hungarian cemeteries, based on data of thematic botanical surveys of 991 cemeteries. Out of the surveyed cemeteries, 553 (56%) harbored protected plants, totaling 306.617 estimated individuals of 92 protected species, belonging to 28 plant families. These species represent 12% of the entire protected flora of Hungary. Hungarian cemeteries play a key role mainly in preserving steppe and dry grassland plant species. Long-established and large cemeteries harbor more protected plant species than small and newly established ones. Human population size of the settlements correlated negatively with the number of protected species and individuals. Moreover, woodland cover and proportion of grassland also significantly positively affected the number of protected plant species in cemeteries.

Exact Concentration Dependence of the Landolt Time in the Thiourea Dioxide-Bromate Substrate-Depletive Clock Reaction.

The thiourea dioxide (TDO)-bromate reaction has been reinvestigated spectrophotometrically under acidic conditions using phosphoric acid-dihydrogen-phosphate buffer within the pH range of 1.1-1.8 at 1.0 M ionic strength adjusted by sodium perchlorate and at 25 °C. The title system shows a remarkable resemblance to the classical Landolt reaction, namely, the clock species (bromine) may only appear after the substrate TDO is completely consumed. Thus, the title system can be classified as substrate-depletive clock reaction. Despite the well-known slow rearrangement characteristic of TDO in acidic solution, it is surprisingly found that the Landolt time of the title reaction does not depend at all on the age of TDO solution applied. It is, however, shown experimentally that the inverse of Landolt time linearly depends on the initial bromate concentration as well as on the square of the hydrogen ion concentration. In addition to this, it is also noticed that dihydrogen phosphate markedly affects the Landolt time as well, and this feature may easily be taken into consideration by the H2PO4- dependence of the rate of bromate-bromide reaction quantitatively. Based on the experiments, a simple three-step kinetic model is proposed from which a complex formula is derived to indicate the exact concentration dependence of the Landolt time.

Resurrection and typification of Elatine campylosperma (Elatinaceae), a long-forgotten waterwort species.

The name Elatine campylosperma Seub. is generally treated as one of the synonyms of E. macropoda Guss. However, recent morphological, phylogenetic and karyological studies indicate that this judgement should be revised. In the present paper we typify the name E. campylosperma, review its taxonomic history and provide a thorough description, with compilation of previously published data and our new measurements from in vitro cultures. Based on our herbarium survey, we outline its Atlantic-Mediterranean distribution area (Spain, France, Italy, Greece, Turkey and Algeria). Habitat preferences are summarized from our field observations, water quality measurements and the label information of the herbarium specimens examined. Intact E. campylosperma seeds were found in faecal samples of the Eurasian Coot (Fulica atra L.) in southern Spain and two of them were germinated, suggesting that E. campylosperma has a capacity for long distance dispersal via endozoochory.

Roadside verges as habitats for endangered lizard-orchids (Himantoglossum spp.): Ecological traps or refuges?

Alterations in traditional land use practices have led to severe declines in the area of semi-natural grasslands, thereby seriously threatening plant and animal species dependent on these habitats. Small anthropogenic managed habitats, like roadsides can act as refuges and might play an important role in conserving these species. Colonization of roadside verges by endangered lizard orchids (Himantoglossum spp.) has long been known, but few studies have systematically explored the suitability of roadside habitats for these orchids and the impact of roads on them. In this paper we present results of targeted surveys of three lizard orchid taxa on roadsides from eight European countries. During these surveys we searched for lizard orchids inhabiting roadside verges and recorded their distance from road, aspects of the roadside environment, as well as vegetative and reproductive characteristics of individual plants. We found large numbers of lizard orchids on roadside verges. Distance from roads was not uniformly distributed: orchids occurred more closely to roads than expected by chance. This suggests that regular management of roadsides (e.g. mowing) might enhance colonization and survival of lizard orchids. On the other hand, we also found that close proximity to roads negatively affects reproductive success, suggesting that the immediate vicinity of roads might act as an ecological trap (i.e. favorable in terms of colonization and survival but unfavorable in terms of reproduction). Nonetheless, the fact that significant and viable populations are maintained at roadsides suggests that traditionally managed roadside verges may allow long-term persistence of lizard orchid populations and may serve as refuges in a landscape context.

Turkish graveyards as refuges for orchids against tuber harvest.

Harvest of orchid tubers for salep production is widespread in southwestern Asia and the Balkans and constitutes a major conservation risk for wild orchid populations. Synanthropic habitats, such as graveyards, are important refuges for orchids and other organisms and could offer protection from salep harvesting because of their special cultural role. However, little is known about the occurrence and factors influencing harvesting of salep in graveyards. During field surveys of 474 graveyards throughout Turkey, we observed 333 graveyards with orchids, 311 graveyards with tuberous orchids, and salep harvest in 14 graveyards. Altogether, 530 individuals of 17 orchid species were collected, representing 9% of the individuals recorded. Harvesting intensity was relatively low, and populations were usually not wholly destroyed. However, some species were clearly more affected than others. Salep harvesting risk of orchid species was significantly associated with flowering time, with early-flowering species being more affected. A marginally significant positive relationship between harvesting risk and species-specific tuber size was also detected. Our data suggest that graveyards might offer some protection against salep harvesting in Turkey, but they also show that some orchid taxa are much more affected than others. Overall, our observations add more weight to the conservation value of these special habitats.

A systematic approach to the synthesis of androstane-based 3,17-dicarboxamides (homo- and mixed dicarboxamides) via palladium-catalyzed aminocarbonylation.

3,17-Dicarboxamido-androst-3,5,16-triene derivatives possessing various amine moieties were synthesized under mild conditions using palladium-catalyzed homogeneous aminocarbonylation as key reaction. Compounds containing the corresponding iodoalkene functionalities, i.e., 17-iodo-16-ene and 3-iodo-3,5-diene structural motifs, were used in the aminocarbonylation and the N-nucleophiles were varied systematically. Three amines, such as tert-butylamine, piperidine and methyl alaninate were used as N-nucleophiles in the aminocarbonylation. All variations of 3,17-dicarboxamides were synthesized using this methodology. Androst-4-ene-3,17-dione was used as starting material. The synthetic strategy of the multistep synthesis was based on the systematic variation and consecutive use of three different reactions: (i) the protection/deprotection of one of the keto functionalities (3-one or 17-one) as ethylene ketals, (ii) the transformation of the other keto group to iodoalkene functionality via its hydrazone, and (iii) palladium-catalyzed aminocarbonylation of the iodoalkene functionality.

Systematic investigation on the synthesis of androstane-based 3-, 11- and 17-carboxamides via palladium-catalyzed aminocarbonylation.

3,17-Dicarboxamido-androst-3,5,16-triene, 3-carboxamido-androst-3,5-dien-17-one, 17-carboxamido-androst-4,16-dien-3-one and 11-carboxamido-androst-5,9(11)-dien-3,17-dione derivatives were synthesized in homogeneous carbonylation reactions from the corresponding 3,17-diiodo-androst-3,5,16-triene, 3-iodo-androst-3,5-diene-17-ethylene ketal, 17-iodo-androst-5,16-dien-3-ethylene ketal, 11-iodo-androst-5,9(11)-diene-3,17-bis(ethylene ketal) derivatives, respectively. A highly chemoselective palladium-catalyzed aminocarbonylation of the corresponding iodo-alkene, carried out under mild reaction conditions, can be considered as the key-step for the introduction of the carboxamide functionalities. The synthesis of the iodo-alkene substrate is based on the transformation of the corresponding keto derivative to hydrazone, which was treated with iodine in the presence of a base (1,1,3,3-tetramethyl guanidine). The aminocarbonylation reaction is highly tolerant towards the N-nucleophiles, i.e. various primary and secondary amines including amino acid methyl esters can also be used.

Novel 13ß- and 13α-D-homo steroids: 17a-carboxamido-D-homoestra-1,3,5(10),17-tetraene derivatives via palladium-catalyzed aminocarbonylations.

17a-Methoxycarbonyl- and 17a-carboxamido-D-homoestra-1,3,5(10),17-tetraene derivatives were synthesized by palladium-catalyzed carbonylation reactions of the corresponding 17a-iodo-D-homoestra-1,3,5(10),17-tetraene derivatives using methanol and various amines as O- and N-nucleophiles, respectively. Both the natural (13ß) and the epi (13α) series of compounds were isolated. The 17a-iodo-17-ene functionalities in the two 13-epimer series differ in reactivity. While the aminocarbonylations were practically complete in the 13ß series in reasonable reaction time under mild conditions and high isolated yields were achieved, the corresponding 13α-17a-iodo-17-ene substrate has shown decreased reactivity resulting in moderate to low yields. However, under high carbon monoxide pressure (40 bar) excellent yields can be obtained even in the 13α series. The aminocarbonylation was completely chemoselective in both series, i.e., the corresponding 17a-carboxamido-17-ene derivatives were formed exclusively.

The synthesis of 13alpha-androsta-5,16-diene derivatives with carboxylic acid, ester and carboxamido functionalities at position-17 via palladium-catalyzed carbonylation.

17-Alkoxycarbonyl- and 17-carboxamido-3beta-hydroxy-13alpha-androsta-5,16-diene derivatives were synthetized in high yields in the palladium-catalyzed carbonylation reactions of the corresponding 3beta-hydroxy-17-iodo-13alpha-androsta-5,16-diene. This substrate with a 17-iodo-16-ene functionality was obtained from the 17-keto derivative via its 17-hydrazone, which was treated with iodine in the presence of a base (1,1,3,3-tetramethylguanidine). 17-Carboxamides were obtained by chemoselective aminocarbonylation through the use of amines, including amino acid esters, as N-nucleophiles. The 17-methoxycarbonyl-16-ene derivative was synthetized by using methanol as O-nucleophile. The parent compound of this series, the 17-carboxylic acid derivative, was formed in the presence of water via hydroxycarbonylation.

The synthesis of 17-alkoxycarbonyl- and 17-carboxamido-13alpha-estra-1,3,5(10),16-tetraene derivatives via palladium-catalyzed carbonylation reactions.

17-Alkoxycarbonyl- and 17-carboxamido-13alpha-estra-1,3,5(10),16-tetraenes were synthesized from the 17-iodo-13alpha-estra-1,3,5(10),16-tetraene derivative in palladium-catalyzed alkoxycarbonylation and aminocarbonylation reactions, respectively. The synthesis of the 17-iodo-16-ene derivative, used as substrate, is based on the transformation of the 17-keto derivative (epiestrone methyl ether) to hydrazone, which was treated with iodine in the presence of a base (1,1,3,3-tetramethyl guanidine). 17-Carboxamides were obtained in good yields (up to 88%) not only with simple alkyl/aryl amines but also with amino acid methyl esters as N-nucleophiles. The use of alcohols as O-nucleophiles in alkoxycarbonylation resulted in the corresponding 17-esters; however, yields of synthetic interest were obtained only with methanol.

Facile synthesis of 11-carboxamido-androst-4,9(11)-dienes via palladium-catalyzed aminocarbonylation.

11-Carboxamido-androst-4,9(11)-dienes were synthesized from the corresponding 11-iodo-androst-4,9(11)-diene derivative in palladium-catalyzed aminocarbonylation reaction under mild reaction conditions. The synthesis of the iodo-alkene substrate is based on the transformation of the 11-keto derivative to hydrazone, which was treated with iodine in the presence of a base (1,1,3,3-tetramethyl guanidine). The 11-carboxamides were synthesized in moderate to high isolated yields by using simple alkyl/arylamines or amino acid methylesters as N-nucleophiles. The highly active palladium catalysts enable the homogeneous catalytic functionalization at one of the most hindered position (C-11) of the steroidal skeleton.