Zinc, aluminum and group 3 metal complexes of sterically demanding naphthoxy-pyridine ligands: Synthesis, structure, and use in ROP of racemic lactide and β-butyrolactone

International audienceNew potentially tridentate, bulky ortho-Ph3Si-substituted naphthol-pyridine proligands a–f were synthesized and introduced onto zinc, aluminum and group 3 metal centers (M = Sc, Y, La) using straightforward one-step alkane or amine elimination protocols. The solid-state structures of these mononuclear zinc (1a, 1c, 1d, 2c and 2e) and aluminum (3c) complexes were determined by single-crystal X-ray diffraction studies, while the solution structures were established using 1H, 13C{1H} and 29Si/29Si{1H} (when appropriate) NMR spectroscopy. For all complexes, only one species (isomer) of C1 symmetry was observed by NMR spectroscopy in the broad temperature range. Most of these complexes are effective initiators for the ring-opening polymerization (ROP) of racemic lactide (rac-LA) at 25–100 °C, affording poly(lactides)s (PLAs) generally with unimodal dispersities and molecular weights in good agreement with calculated values. An yttrium complex (4e) proved the most active (TOF = 1840 mol(LA) mol(Y)−1 h−1 at 25 °C) and yielded heterotactic-enriched PLAs (Pr up to 0.80) in toluene, while atactic PHBs were formed in the ROP of racemic β-butyrolactone (rac-BBL) under the same conditions

Bioerosion of siliceous rocks driven by rock-boring freshwater insects

Macrobioerosion of mineral substrates in fresh water is a little-known geological process. Two examples of rock-boring bivalve molluscs were recently described from freshwater environments. To the best of our knowledge, rock-boring freshwater insects were previously unknown. Here, we report on the discovery of insect larvae boring into submerged siltstone (aleurolite) rocks in tropical Asia. These larvae belong to a new mayfly species and perform their borings using enlarged mandibles. Their traces represent a horizontally oriented, tunnel-like macroboring with two apertures. To date, only three rock-boring animals are known to occur in fresh water globally: a mayfly, a piddock, and a shipworm. All the three species originated within primarily wood-boring clades, indicating a simplified evolutionary shift from wood to hardground substrate based on a set of morphological and anatomical preadaptations evolved in wood borers (e.g., massive larval mandibular tusks in mayflies and specific body, shell, and muscle structure in bivalves)

New chiral yttrium complexes for asymmetric intramolecular hydroamination of aminoalkenes

Les hétérocycles azotés chiraux représentent une classe importante de composés biologiquement actifs. L’hydroamination asymétrique intramoléculaire correspond parfaitement au concept d’économie d’atomes et permet l’accès direct à la formation de nouvelles liaisons carbone-azote. Le développement de catalyseurs pour la formation de pyrrolidines et piperidines reste cependant une tâche importante. Le thème de cette thèse est l’étude de nouveaux complexes chiraux binaphthylamide d’yttrium facilement accessibles et leur application pour promouvoir la réaction d’hydroamination/cyclisation des amines primaires liées à des alcènes stériquement encombrés.Des complexes chiraux binaphthylamidure alkyl ate d’yttrium ont été développés. Ces systèmes catalytiques ont été préparés in situ par une réaction simple stœchiométrique en présence d’un précurseur d’yttrium [Li(THF)4][Y(CH2SiMe3)4] connu et d’une variété de ligands chiraux binaphthyldiamine substitués. Les complexes chiraux hétéroleptiques obtenus se sont révélés actifs et énantiosélectifs pour la réaction d’hydroamination asymétrique intramoléculaire des aminoalcènes 1,2-disubstitués conduisant à la formation d’hétérocycles azotés avec cinq et six châinons. Les catalyseurs d’yttrium préparés à partir du ligand (R)-N-anthrylmethyl-binaphthylamine H2L13 et des ligands (R)-benzyl N-para-substitués H2L4 or H2L6 se sont révélés les plus énantiosélectifs à 70-110°C pour la réaction d’hydroamination/cyclisation des aminoalcènes encombrés. Un excès énantiomérique de 77% a été obtenu comme valeur la plus élevée décrite jusqu’à présent pour l’hydroamination asymétrique intramoléculaire des amines comportant des alcènes 1,2-disubstitués. Les premiers exemples de la réaction d’hydroamination intramoléculaire asymétrique des aminoalcènes 1,1,2-trisubstitués ont été rapportés. Les complexes ate alkyl d’yttrium ont fourni les produits hétérocycliques avec des centres quaternaires énantiomériquement enrichis dans des conditions réactionelles plus sévères que la cyclisation des aminoalcènes 1,2-disubstitués et avec des énantiosélectivités prometteuses atteignant 55%. Les complexes alkyl d’yttrium contenant une molécule de chlorure de lithium [{(R)-C20H12(NSiMe3)2}Y{CH2SiMe3}{LiCl(THF)2}] and [{(R)-C20H12(NC5H9)2}Y{CH2SiMe3}{LiCl(THF)2}] ont été préparés et comparés aux mêmes complexes sans LiCl. Ils se sont révélés être des catalyseurs efficaces pour la réaction d’hydroamination intramoléculaire des aminoalcènes terminaux.Chiral nitrogen-containing heterocycles represent an important class of biologically active compounds. The asymmetric intramolecular hydroamination perfectly matches the concept of sustainable chemistry and allows the formation of new nitrogen-carbon bonds in an ideal atom efficiency and economy, starting from non activated substrates. The development of catalysts for formation of enantioenriched pyrrolidines and piperidines derivatives remains however a challenging task. The topic of this dissertation is the study of new easily accessible chiral yttrium binaphthylamide complexes and their application for promoting the hydroamination/cyclisation of primary amines tethered to sterically demanding alkenes. Chiral binaphthylamido alkyl ate yttrium complexes have been investigated. These catalytic systems have been prepared by a facile in situ stoichiometric reaction of a well-known yttrium precursor [Li(THF)4][Y(CH2SiMe3)4] with a variety of chiral substituted (R)-binaphthylamine ligands. These chiral heteroleptic complexes are shown to be efficient catalysts for the enantioselective intramolecular hydroamination of 1,2-disubstituted aminoalkenes leading to the formation of five and six-membered N-heterocycles. Yttrium catalysts prepared from (R)-N-anthrylmethyl-binaphthylamine ligand H2L13 and (R)-N-para-substituted benzyl ligands H2L4 or H2L6 proved to be the most enantioselective catalysts at 70-110°C for the hydroamination/cyclisation of challenging aminoalkenes. An enantiomeric excess value of 77 % was indeed disclosed as the highest value reported so far for the asymmetric intramolecular hydroamination of amines tethered to 1,2-disubstituted alkenes. The first examples of asymmetric intramolecular hydroamination of 1,1,2-tri-substituted aminoalkenes have been reported. The alkyl ate yttrium complexes produced the heterocyclic compounds with enantioenriched quaternary centres under harsher reaction conditions than the cyclisation of the corresponding 1,2-disubstituted alkenes, and with promising enantioselectivities of up to 55 %.The neutral alkyl yttrium complexes containing one molecule of lithium chloride [{(R)-C20H12(NSiMe3)2}Y{CH2SiMe3}{LiCl(THF)2}] and [{(R)-C20H12(NC5H9)2}Y{CH2SiMe3}{LiCl(THF)2}] have been prepared and compared with the same complexes lacking LiCl. They have been revealed as efficient catalysts for intramolecular hydroamination of terminal aminoalkenes

New chiral yttrium complexes for asymmetric intramolecular hydroamination of aminoalkenes

Les hétérocycles azotés chiraux représentent une classe importante de composés biologiquement actifs. L hydroamination asymétrique intramoléculaire correspond parfaitement au concept d économie d atomes et permet l accès direct à la formation de nouvelles liaisons carbone-azote. Le développement de catalyseurs pour la formation de pyrrolidines et piperidines reste cependant une tâche importante. Le thème de cette thèse est l étude de nouveaux complexes chiraux binaphthylamide d yttrium facilement accessibles et leur application pour promouvoir la réaction d hydroamination/cyclisation des amines primaires liées à des alcènes stériquement encombrés.Des complexes chiraux binaphthylamidure alkyl ate d yttrium ont été développés. Ces systèmes catalytiques ont été préparés in situ par une réaction simple stœchiométrique en présence d un précurseur d yttrium [Li(THF)4][Y(CH2SiMe3)4] connu et d une variété de ligands chiraux binaphthyldiamine substitués. Les complexes chiraux hétéroleptiques obtenus se sont révélés actifs et énantiosélectifs pour la réaction d hydroamination asymétrique intramoléculaire des aminoalcènes 1,2-disubstitués conduisant à la formation d hétérocycles azotés avec cinq et six châinons. Les catalyseurs d yttrium préparés à partir du ligand (R)-N-anthrylmethyl-binaphthylamine H2L13 et des ligands (R)-benzyl N-para-substitués H2L4 or H2L6 se sont révélés les plus énantiosélectifs à 70-110C pour la réaction d hydroamination/cyclisation des aminoalcènes encombrés. Un excès énantiomérique de 77% a été obtenu comme valeur la plus élevée décrite jusqu à présent pour l hydroamination asymétrique intramoléculaire des amines comportant des alcènes 1,2-disubstitués. Les premiers exemples de la réaction d hydroamination intramoléculaire asymétrique des aminoalcènes 1,1,2-trisubstitués ont été rapportés. Les complexes ate alkyl d yttrium ont fourni les produits hétérocycliques avec des centres quaternaires énantiomériquement enrichis dans des conditions réactionelles plus sévères que la cyclisation des aminoalcènes 1,2-disubstitués et avec des énantiosélectivités prometteuses atteignant 55%. Les complexes alkyl d yttrium contenant une molécule de chlorure de lithium [{(R)-C20H12(NSiMe3)2}Y{CH2SiMe3}{LiCl(THF)2}] and [{(R)-C20H12(NC5H9)2}Y{CH2SiMe3}{LiCl(THF)2}] ont été préparés et comparés aux mêmes complexes sans LiCl. Ils se sont révélés être des catalyseurs efficaces pour la réaction d hydroamination intramoléculaire des aminoalcènes terminaux.Chiral nitrogen-containing heterocycles represent an important class of biologically active compounds. The asymmetric intramolecular hydroamination perfectly matches the concept of sustainable chemistry and allows the formation of new nitrogen-carbon bonds in an ideal atom efficiency and economy, starting from non activated substrates. The development of catalysts for formation of enantioenriched pyrrolidines and piperidines derivatives remains however a challenging task. The topic of this dissertation is the study of new easily accessible chiral yttrium binaphthylamide complexes and their application for promoting the hydroamination/cyclisation of primary amines tethered to sterically demanding alkenes. Chiral binaphthylamido alkyl ate yttrium complexes have been investigated. These catalytic systems have been prepared by a facile in situ stoichiometric reaction of a well-known yttrium precursor [Li(THF)4][Y(CH2SiMe3)4] with a variety of chiral substituted (R)-binaphthylamine ligands. These chiral heteroleptic complexes are shown to be efficient catalysts for the enantioselective intramolecular hydroamination of 1,2-disubstituted aminoalkenes leading to the formation of five and six-membered N-heterocycles. Yttrium catalysts prepared from (R)-N-anthrylmethyl-binaphthylamine ligand H2L13 and (R)-N-para-substituted benzyl ligands H2L4 or H2L6 proved to be the most enantioselective catalysts at 70-110C for the hydroamination/cyclisation of challenging aminoalkenes. An enantiomeric excess value of 77 % was indeed disclosed as the highest value reported so far for the asymmetric intramolecular hydroamination of amines tethered to 1,2-disubstituted alkenes. The first examples of asymmetric intramolecular hydroamination of 1,1,2-tri-substituted aminoalkenes have been reported. The alkyl ate yttrium complexes produced the heterocyclic compounds with enantioenriched quaternary centres under harsher reaction conditions than the cyclisation of the corresponding 1,2-disubstituted alkenes, and with promising enantioselectivities of up to 55 %.The neutral alkyl yttrium complexes containing one molecule of lithium chloride [{(R)-C20H12(NSiMe3)2}Y{CH2SiMe3}{LiCl(THF)2}] and [{(R)-C20H12(NC5H9)2}Y{CH2SiMe3}{LiCl(THF)2}] have been prepared and compared with the same complexes lacking LiCl. They have been revealed as efficient catalysts for intramolecular hydroamination of terminal aminoalkenes.PARIS11-SCD-Bib. électronique (914719901) / SudocSudocFranceF

A new genus and species of planthopper from Seychelles endemic palm forest (Hemiptera: Fulgoromorpha: Derbidae)

Bolotov, Ivan N., Kolosova, Yulia S., Chapurina, Yulia E., Spitsyna, Elizaveta A., Spitsyn, Vitaly M. (2021): A new genus and species of planthopper from Seychelles endemic palm forest (Hemiptera: Fulgoromorpha: Derbidae). Journal of Natural History 55 (19-20): 1311-1321, DOI: 10.1080/00222933.2021.1947536, URL: http://dx.doi.org/10.1080/00222933.2021.194753

From Syndiotactic Homopolymers to Chemically Tunable Alternating Copolymers: Highly Active Yttrium Complexes for Stereoselective Ring-Opening Polymerization of β-Malolactonates

International audienceAlternating copolymers constitute an attractive class of materials. It was shown previously that highly alternated poly(β-hydroxyalkanoate)s (PHAs) can be prepared by ring-opening polymerization (ROP) of mixtures of two different enantiomerically pure 4-alkyl-β-propiolactones. However, the approach could not be extended to PHAs with chemically tunable functional groups, which is highly desirable to access original advanced materials. Reported herein is the first highly syndioselective and controlled ROP of racemic allyl and benzyl β-malolactonates (MLAR; R=allyl, benzyl) using an yttrium complex supported by a tetradentate dichloro-substituted bis(phenolate) ligand. This highly active catalyst allows the nearly perfect alternating copolymerization of MLAAllyl and MLABenzyl. Hydrogenolysis of the benzyloxycarbonyl or functionalization of the allyl pendant groups opens a route towards a new class of functional alternating copolymers

Scandium versus yttrium{amino-alkoxy-bis(phenolate)} complexes for the stereoselective ring-opening polymerization of racemic lactide and β-butyrolactone.

International audienceScandium and yttrium amide complexes Ln{ONXO(R1,R2)}(N(SiHMe2)2)(THF)n (Ln = Sc, n = 0 or Y, n = 1; X = NMe2 or OMe; R(1) = Cumyl or p-Cl-Cumyl; R(2) = Me or Cumyl) were prepared by aminolysis of Ln[N(SiHMe2)2]3(THF) with the corresponding tetradentate diamino- or alkoxy-amino-bis(phenol) pro-ligands {ONXO(R1,R2)}H2. In the solid state and in toluene solution, the scandium complexes are monomeric and 5-coordinated, while the analogous yttrium complexes all bear an extra THF-coordinated molecule and are 6-coordinated. Sc{ONXO(R1,R2)}(N(SiHMe2)2) complexes are single-site initiators for the ring-opening polymerization (ROP) of racemic lactide but are less active than their yttrium analogues Y{ONXO(R1,R2)}(N(SiHMe2)2)(THF); also, in contrast to the latter ones, they are inactive in the ROP of the more demanding racemic β-butyrolactone. On the other hand, the scandium amide complexes feature a significantly improved control over the ROP of lactide, yielding PLAs with much narrower molecular weight distributions (Đ(M) < 1.1 for Sc vs. 1.5-2.0 for Y). The yttrium complex with the very bulky o,p-dicumyl-substituted ligand is more heteroselective than its scandium analogue (P(r) = 0.88 vs. 0.83), while the opposite is observed with complexes based on p-methyl-substituted ligands (P(r) = 0.50 in toluene or 0.72-0.75 in THF for Y vs. P(r) = 0.75-0.83 for Sc in toluene). These reactivity and selectivity trends are rationalized by a much more sterically crowded coordination sphere in scandium than in yttrium complexes

Synthesis of Thrombolytic Sol–Gel Coatings: Toward Drug-Entrapped Vascular Grafts

As is evident from numerous investigations, drug-eluting vascular grafts and stents have not solved the main problems associated with thrombosis and due to drug release only postpone their advance for a longer period. Here we point to a potential solution of this problem by developing thrombolytic sol–gel coatings which potentially could lead to drug-entrapped vascular grafts: urokinase-type plasminogen activator was entrapped within a porous alumina sol–gel film with a subsequent deposition on a polymer graft

New Molecular-Based Phylogeny of Mussel-Associated Mites Reveals a New Subgenus and Three New Species Representing an Example of a Host-Driven Radiation in Indochina and Confirms the Concept of Division of the Genus Unionicola Haldeman, 1842 (Acari: Unionicolidae) into Numerous Subgenera

Here we describe a new subgenus and three new species of parasitic water mites in the genus Unionicola (Acari: Hydrachnidia) from Myanmar: Myanmaratax&nbsp;subgen. nov., Unionicola (Myanmaratax) savadiensis&nbsp;subgen. and sp. nov. (hosts: Lamellidens savadiensis and L. generosus), U. (My.) generosa&nbsp;sp. nov. (the same hosts), and U. (My.) trapezidenssp. nov. (hosts: Trapezidens dolichorhynchus and T. angustior). These taxa were identified based on a two-gene phylogenetic analysis (COI + 28S), which also confirms the division of the genus Unionicola into numerous subgenera. The new species are cryptic species, which are morphologically indistinguishable but strongly resemble U. (Prasadatax) brandti Vidrine, 1985 described from Thailand (hosts: Lens spp. and Ensidens spp.). We also transfer the latter taxon from Prasadatax to Myanmaratax based on a set of morphological evidence and propose U. (My.) brandti&nbsp;comb. nov. The new subgenus contains a total of five species, one of which needs future sampling efforts and will be described elsewhere. Additionally, 56 valid subgenera, which were placed in the synonymy of the genus and in one case raised to the genus level, are restored here until robust phylogenetic evidence on their taxonomic status is available. Our results also confirm that Unionicola mites are narrow host specialists that are associated with either one or a few closely related freshwater mussel species belonging to one or two sister genera

A freshwater mussel species reflects a Miocene stream capture between the Mekong Basin and East Asian rivers

Freshwater mussels belonging to the genus Cristaria Schumacher, 1817 (Bivalvia: Unionidae) are widespread from Mongolia to Indochina while the range of one species, C. plicata (Leach, 1814), covers two biogeographic subregions, i.e., East Asian (Amur River to Vietnam) and Sundaland (Mekong River basin). We present here a taxonomic revision of the nominal taxon Anodonta bellua Morelet, 1866 which was described from the Mekong (Lake Tonle-Sap, Cambodia) but is currently considered a synonym of C. plicata. We obtained molecular data for newly collected Cristaria representatives from the Mekong’s tributaries in Laos, which were found as a divergent species-level phylogenetic clade within the genus that is distant from C. plicata. Nevertheless, comparative morphological and morphometric studies did not reveal any significant differences between these two congeners. Our time-calibrated biogeographic modeling reveals that the split between Cristaria bellua (Mekong) and C. clessini (East Asia) probably occurred in the mid-Miocene (15.8 Ma) and may reflect an ancient stream capture between the Mekong Basin and East Asian rivers