Coinage Metal-Catalyzed Asymmetric Reactions of ortho-Alkynylaryl and Heteroaryl Aldehydes and Ketones.

Coinage metals have become the metal of choice due to their excellent catalytic activity in organic transformation processes. Combining various chiral ligands and coinage metals became a productive area of research and access to heterocyclic derivatives according to an efficient and sustainable manner. This review was devoted to the various recently developed coinage metal-catalyzed domino processes of ortho-alkynylaryl and heteroaryl aldehydes and ketones leading to functionalized heterocycles. Various gold chiral complexes were presented, and methods of preparations of chromenes along with indoles were covered. Ag-chiral complexes are also prone to interesting activities such as cyclization followed by reduction and functionalization with enolizable ketones or (diazomethyl)phosphonate. Asymmetric Cu-catalyzed domino cyclization and asymmetric transfer hydrogenation reactions efficiently led to functionalized chromenes. Some remarkable examples involving copper associated with ruthenium in the context of a cyclization and asymmetric hydrogenation process were also presented.

Diversity of farmland management practices (FMP) and their nexus to environment: A review.

We examined the environmental impacts of farmland management practices (FMPs), considering FMPs as frequent or single actions that change both land use AND use rights (land and property relations). Based on a review of the international literature in both the social and life sciences and using an analytical framework of landscape agronomy, we explored the links between FMPs and changes in agricultural practices designed for the achievement of environmental goals. The Web of Science (WOS) and SCOPUS bibliographic databases were used to identify references on FMP types and their environmental effects based on the following search equations: 1- " Farmland tenure OR cropland tenure OR farm size and environment " and 2- "Farmland use rights OR farmland property rights AND environment OR pollution OR biodiversity." Ninety references were selected from these databases and read in depth. Google scholar enabled us to identify an additional 20 papers, using the snowball approach. From this analysis, we present a typology of FMPs based on the distinction between bottom-up strategies, which rely on local initiatives from farmers to improve the overall functioning of their farms, and top-down strategies, which originate from public bodies or private organizations. Our results also highlight the environmental impacts of FMPs considered in the literature: tenure arrangements, whether rental or exchange of land parcels, may alter crop succession and reduce phytosanitary pressure without changing cropping plans. Considering the direct agronomic implications of farmers' land dynamics, we conclude that the area of FMPs is a potential tool for reducing the environmental impacts of agricultural activities and protecting natural resources. This is the subject of ongoing research that seeks to explore a particular FMP in greater depth, along with temporary exchanges of plots between farmers as an agri-environmental tool to reduce agricultural impacts on environment.

Regioselective trans-Hydrostannation of Boron-Capped Alkynes.

Alkynyl-B(aam) (aam=anthranilamidato) derivatives are readily available bench-stable compounds that undergo remarkably selective reactions with Bu3 SnH in the presence of [Cp*RuCl]4 as the catalyst. The addition follows a stereochemically unorthodox trans-selective course; in terms of regioselectivity, the Bu3 Sn- unit is delivered with high fidelity to the C-atom of the triple bond adjacent to the boracyclic head group ("alpha,trans-addition"). This outcome is deemed to reflect a hydrogen bonding interaction between the protic -NH groups of the benzo-1,3,2-diazaborininone ring system and the polarized [Ru-Cl] bond in the loaded catalyst, which locks the substrate in place in a favorable orientation relative to the incoming reagent. The resulting isomerically (almost) pure gem-dimetalated building blocks are amenable to numerous downstream functionalizations; most remarkable is the ability to subject the -B(aam) moiety to Suzuki-Miyaura cross coupling without need for prior hydrolysis while keeping the adjacent Bu3 Sn- group intact. Alternatively, the tin residue can be engaged in selective tin/halogen exchange without touching the boron substituent; the fact that the two -NH entities of -B(aam) do not protonate organozinc reagents and hence do not interfere with Negishi reactions of the alkenyl halides thus formed is another virtue of this so far underutilized boracycle. Overall, the ruthenium catalyzed trans-hydrostannation of alkynyl-B(aam) derivatives opens a practical gateway to isomerically pure trisubstituted alkenes of many different substitution patterns by sequential functionalization of the 1-alkenyl-1,1-heterobimetallic adducts primarily formed.

Palladium(0)-Catalyzed Enantioselective Intramolecular Arylation of Enantiotopic Secondary C-H Bonds.

The enantioselective functionalization of nonactivated enantiotopic secondary C-H bonds is one of the greatest challenges in transition-metal-catalyzed C-H activation proceeding by an inner-sphere mechanism. Such reactions have remained elusive within the realm of Pd0 catalysis. Reported here is the unique reactivity profile of the IBiox ligand family in the Pd0 -catalyzed intramolecular arylation of such nonactivated secondary C-H bonds. Chiral C2 -symmetric IBiox ligands led to high enantioselectivities for a broad range of valuable indane products containing a tertiary stereocenter, as well as the arylation of secondary C-H bonds adjacent to amides. Depending on the amide substituents and upon control of reaction time, indanes containing labile tertiary stereocenters were also obtained with high enantioselectivities. Analysis of the steric maps of the IBiox ligands indicated that the level of enantioselectivity correlates with the difference between the two most occupied and the two less occupied space quadrants, and provided a blueprint for the design of even more efficient ligands.

Total Synthesis of (Nor)illudalane Sesquiterpenes Based on a C(sp3)-H Activation Strategy.

Three (nor)illudalane sesquiterpenes were synthesized from a common intermediate in racemic and enantioenriched forms using Pd0-catalyzed C(sp3)-H arylation as a key step. The configuration of the isolated, highly symmetric quaternary stereocenter of the target molecules was controlled through a matched combination of chiral substrate and catalyst. Moreover, the recently developed Ir-catalyzed C-H borylation/Cu-catalyzed methylation method was employed to install the methyl group on the benzene ring. This strategy allowed the efficient synthesis of both racemic and (S)-configured puraquinonic acid, deliquinone, and russujaponol F.

Divergent Enantioselective Synthesis of (Nor)illudalane Sesquiterpenes via Pd0-Catalyzed Asymmetric C(sp3)-H Activation.

A divergent enantioselective synthesis of (nor)illudalane sesquiterpenes was designed by using a Pd0-catalyzed asymmetric C(sp3)-H arylation as a key step to control the isolated, highly symmetric quaternary stereocenter of the target molecules. A matched combination of chiral substrate and catalyst proved optimal to reach good levels of stereoselectivity. This approach enabled the synthesis of three (nor)illudalanes, including ( S)-deliquinone and ( S)-russujaponol F, which are synthesized for the first time in enantioenriched form.

Palladium(0)-catalyzed asymmetric C(sp3)-H arylation using a chiral binol-derived phosphate and an achiral ligand.

The first efficient palladium(0)-catalyzed enantioselective C(sp3)-H activation reaction using a catalytic chiral base and an achiral phosphine ligand is reported. Fine-tuning the binol-derived phosphoric acid pre-catalyst and the reaction conditions was found to be crucial to achieve high levels of enantioselectivity for a variety of indoline products containing both tri- and tetrasubstituted stereocenters.

Palladium-Catalyzed C(sp(2))-H Alkylation of Aldehyde-Derived Hydrazones with Functionalized Difluoromethyl Bromides.

A palladium-catalyzed C(sp(2))-H difluoromethylation of aldehyde-derived hydrazones using bromodifluoromethylated compounds to afford the corresponding functionalized difluoromethylketone hydrazones has been established. It is proposed that a radical/SET mechanism proceeding via a difluoroalkyl radical may be involved in the catalytic cycle. Applications of the methodology to the synthesis of α,α-difluoro-ß-ketoesters and α,α-difluoroketones (RCOCF2 H) have been illustrated.

Identifying and measuring land-use and proximity conflicts: methods and identification.

ABSTRACT: This text aims to present the methodology of study of land-use conflicts performed in recent years by a multidisciplinary team, and to reveal the methods of survey and data collection, as well as the structure of the resulting database. We first define the scope of our study by providing a definition of these conflicts, of their characteristics and motives, of the ways they manifest themselves and of the actors involved (I). We then present the methodology we have used to identify conflicts; it is based on a spatial analysis and the combined use of different data collection methods including surveys conducted by experts, analyses of the regional daily press and of data from the administrative litigation courts (II). Finally we present the resulting Conflicts © data base, with its tables and nomenclatures, in which the data collected in different fields are reconciled and analyzed (III), before providing a few examples of how this method can be used to analyze case studies in developed and developing countries (IV). JEL CODES: D74; C83; K41.