Impacts of Perfluoroalkyl Substances on Aqueous and Nonaqueous Phase Liquid Dechlorination by Sulfidized Nanoscale Zerovalent Iron.

Per- and poly fluoroalkyl substances (PFASs) are often encountered with nonaqueous phase liquid (NAPL) in the groundwater at fire-fighting and military training sites. However, it is unclear how PFASs affect the dechlorination performance of sulfidized nanoscale zerovalent iron (S-nFe), which is an emerging promising NAPL remediation agent. Here, S-nFe synthesized with controllable S speciation (FeS or FeS) were characterized to assess their interactions with PFASs and their dechlorination performance for trichloroethylene NAPL (TCE-NAPL).

Particle-Scale Understanding of Arsenic Interactions with Sulfidized Nanoscale Zerovalent Iron and Their Impacts on Dehalogenation Reactivity.

Co-occurrence of organic contaminants and arsenic oxoanions occurs often at polluted groundwater sites, but the effect of arsenite on the reactivity of sulfidized nanoscale zerovalent iron (SNZVI) used to remediate groundwater has not been evaluated. Here, we study the interaction of arsenite [As(III)] with SNZVI at the individual-particle scale to better understand the impacts on the SNZVI properties and reactivity. Surface and intraparticle accumulation of As was observed on hydrophilic FeS-Fe and hydrophobic FeS-Fe particles, respectively.

Tailoring Fe Nanoparticles via Lattice Engineering for Environmental Remediation.

Lattice engineering of nanomaterials holds promise in simultaneously regulating their geometric and electronic effects to promote their performance. However, local microenvironment engineering of Fe nanoparticles (nFe) for efficient and selective environmental remediation is still in its infancy and lacks deep understanding. Here, we present the design principles and characterization techniques of lattice-doped nFe from the point of view of microenvironment chemistry at both atomic and elemental levels, revealing their crystalline structure, electronic effects, and physicochemical properties.

Bora-alkenes: Metal Coordination and Reactions with BH-boranes.

The neutral N-heterocyclic carbene stabilized bora-alkene 1, conveniently prepared by a BH borenium/hydroboration route, forms stable copper, gold or palladium π-complexes. The polar bora-alkene B=C system undergoes regioselective hydroboration reactions with the (C F ) BH or C F BH  ⋅ SMe boranes. The latter reaction involves a subsequent rearrangement that leads to internal hydride vs.

Boraalkenes Made by a Hydroboration Route: Cycloaddition and B=C Bond Cleavage Reactions.

Hydroboration of styrene or vinylcyclohexane with the IMes(C F )BH cation followed by deprotonation provided a convenient synthetic entry to the [B]=CHCH R boraalkenes 9 a and 9 b. The in situ generated IMes(SCN)BH system reacted similarly with 1,1-diphenylethene followed by deprotonation to give the isothiocyanato substituted boraalkene 9 c. The boraalkenes underwent [2+2] cycloaddition reactions with a small series of heterocumulenes to give the respective four-membered heterocycles.

Generation of boryl-nitroxide radicals from a boraalkene the nitroso ene reaction.

Examples of isolated boron substituted nitroxide radicals are rare. The reaction of the reactive cyclic boraalkene 3 with nitrosobenzene yields a mixture of the [2 + 2] cycloaddition product 4a, the -nitroxide radicals 5a and 6a and the azoxybenzene co-product 7a a bora nitroso ene reaction pathway, the boron analogue of the nitroso ene reaction. The products were separated by flash chromatography, and the -nitroxide radicals were characterized by X-ray diffraction and EPR spectroscopy.

A deprotonation pathway to reactive [B]CH boraalkenes.

The BH compounds IMes(Ar)BH(NTf) (Ar: CF or FpXyl) were converted to the IMes(Ar)BCH boraalkenes in a three step reaction sequence of B-methylation with methyllithium, hydride abstraction and deprotonation. The BCH boraalkenes reacted with elemental sulfur to give a thiaborirane product. They underwent [2+2] cycloaddition reactions with carbon dioxide or sulfur dioxide to give four-membered boron containing heterocycles.

N-Heterocyclic Carbene Stabilized 1-Bora-1,3-butadienes.

Deprotonation of [(NHC)(Fmes)B-allyl] borenium cations (NHC, IMes () or IMe (); Fmes, 2,4,6-(CF)CH) provides an easy entry to the NHC-stabilized 1-bora-1,3-butadienes. They feature a planar s-trans-conformation just like 1,3-butadiene. The 1-borabutadiene undergoes hydroboration reactions; the HB(CF) hydroboration product is trapped with CO or an isonitrile to give the respective cyclic zwitterionic borenium-borate enolate or enamide products.

Formation and Cycloaddition Reactions of a Reactive Boraalkene Stabilized Internally by N-Heterocyclic Carbene.

The synthesis of element-carbon double bonds is of great importance for the development and understanding of reactive π-bonded systems in chemistry. The seven-membered heterocyclic system 4 b is readily made by internal C-H activation at a pendent isopropyl methyl group of the respective [(IPr)C F BH] borenium ion. Subsequent deprotonation with the IMes carbene gives the neutral cyclic boraalkene system 5 b.

A BH Borenium-Derived Thioxoborane, Its Persulfide, and Their Li-Induced Reactions with Alkynes and with Carbon Dioxide.

Insertion of sulfur into the B-H bond of the BH borenium salt [IMes(CF)BH] followed by deprotonation gave the thioxoborane IMes(CF)B═S. Subsequent treatment with additional sulfur gave the corresponding boron persulfide, a NHC-stabilized boradithiirane. The B═S compound reacted with carbon dioxide in the presence of the lithium salt Li[B(CF)] by formal [2+2] cycloaddition to give a boron thiocarbonate-type product.

The [(NHC)B(H)C F ] Cations and Their [B](H)-CO Borane Carbonyls.

Hydride abstraction from the heterocyclic carbene borane adducts (NHC)BH C F (NHC: IMes or IMe ) gave the B-H containing [(NHC)B(H)C F ] borenium cations. They added carbon monoxide to give the respective [(NHC)B(H)(C F )CO] boron carbonyl cations. Carbon nucleophiles add to the boron carbonyl to give [B](H) acyls.

A rare olefin 1,1-carboboration reaction opens a synthetic pathway to an unusually structured frustrated Lewis pair.

(2,6-Dimesitylphenyl)P(vinyl)5d reacts with HB(CF) in a sequence involving a rare example of a 1,1-carboboration of an olefin to give the borylated tetrahydrophosphole derivative 6d. Compound 6d is an active frustrated Lewis pair that splits dihydrogen under mild conditions and serves as a metal-free hydrogenation catalyst. It also adds to carbon dioxide.

Palladium(II)-Catalyzed Enantioselective Aminotrifluoromethoxylation of Unactivated Alkenes using CsOCF as a Trifluoromethoxide Source.

Asymmetric Pd -catalyzed intramolecular aminotrifluoromethoxylation of unactivated alkenes using readily accessible and stable CsOCF as a trifluoromethoxide source has been developed, which affords a wide variety of enantiomerically enriched β-substituted OCF -containing piperidines in good yields. Introducing a sterically bulky group into pyridine-oxazoline (Pyox) ligands is crucial to increasing both reactivity and enantioselectivity for the reaction. Additionally, the reaction features good functional group compatibility and mild reaction conditions.

Enantioselective Pd(II)-Catalyzed Intramolecular Oxidative 6- endo Aminoacetoxylation of Unactivated Alkenes.

A novel asymmetric 6-endo aminoacetoxylation of unactivated alkenes by palladium catalysis, which yields chiral β-acetoxylated piperidines with excellent chemo-, regio- and enantioselectivities under very mild reaction conditions, has been established herein by employing a new designed pyridine-oxazoline (Pyox) ligand. Importantly, introducing a sterically bulky group into the C-6 position of Pyox is crucial to enhance the reactivity of the aminoacetoxylation of alkenes.

Palladium-Catalyzed Intermolecular Ditrifluoromethoxylation of Unactivated Alkenes: CFO-Palladation Initiated by Pd(IV).

A novel palladium-catalyzed intermolecular ditrifluoromethoxylation of unactivated alkenes has been developed, using a new electrophilic reagent, Selectfluor, as a strong oxidant, and AgOCF as a trifluoromethoxide source. Preliminary mechanistic studies revealed that the reaction was possibly initiated by Pd(IV) species, and an unusual cis-addition of CFO-Pd(IV) into the double bond leads to the formation of the first C-OCF bond; in addition, the second C-OCF bond was produced through reductive elimination at high-valent palladium center.

Palladium-Catalyzed Intramolecular Aminotrifluoromethoxylation of Alkenes.

The first catalytic trifluoromethoxylation of unactivated alkenes has been developed, in which Pd(CH3CN)2Cl2 was used as catalyst, AgOCF3 as trifluoromethoxide source, and Selectfluor-BF4 as oxidant. A variety of 3-OCF3 substituted piperidines were selectively obtained in good yields. Direct evidence was provided to address the facile reductive elimination of Pd(IV)-OCF3 complex to form sp(3) C-OCF3 bond.

Copper-catalyzed trifluoromethylselenolation of aryl and alkyl halides: the silver effect in transmetalation.

A catalytic trifluoromethylselenolation of aryl and alkyl halides by a Cu(I) catalyst has been developed. A key intermediate, [(phen)Cu(SeCF3)]2 (5) was successfully isolated and characterized by X-ray diffraction. The important role of silver in the transmetalation process during the catalytic cycle was elucidated.

Synthesis of Cu(I) trifluoromethylselenates for trifluoromethylselenolation of aryl and alkyl halides.

The development of new strategies for synthesis of trifluoromethylthiolate compounds is of considerable importance in pharmaceuticals, agrochemicals, and advanced materials. Accordingly, currently much attention is being devoted to the development of effective methods and reagents for their synthesis. In contrast, considerably less effort has been afforded to the development of preparing CSeCF3 bonds.

Synthesis of Copper(I) Thiolate Complexes in the Thioetherification of Aryl Halides.

The copper(I) thiophenolato complexes 1-3 containing 1,10-phenanthroline (phen) and 2,9-dimethyl-1,10-phenanthroline (Me(2)phen) were isolated in excellent yields from reactions of [CuOtBu](4) with the dative ligands and subsequent addition of 1 equiv of arylthiol and characterized spectroscopically. X-ray structural analysis of a single crystal of [(phen)Cu(µ-SC(6)H(5))](2) (1) revealed that this complex adopts a neutral dimeric form with a weak Cu-Cu bonding interaction. These complexes were found to react with iodoarenes to form aryl sulfide products.

Thermosensitive hydrogels composed of hyaluronic acid and gelatin as carriers for the intravesical administration of cisplatin.

The aim of this work was to evaluate the use of thermosensitive hydrogels for intravesical cisplatin delivery into the bladder. Poly(N-isopropylacrylamide) (PNIPAM) was grafted onto hyaluronic acid (HA) to synthesize an HPN copolymer, which was further grafted with gelatin to form an HPNG copolymer. A 3% concentration of HPN and HPNG was sufficient to exert a thermosensitive response, whereas a concentration of 8% was needed for PNIPAM to form the hydrogel.

Intravesical delivery of 5-aminolevulinic acid from water-in-oil nano/submicron-emulsion systems.

The present work reports on the development of water-in-oil (w/o) emulsions for the intravesical administration of 5-aminolevulinic acid (ALA). The physicochemical properties of droplet size, zeta potential, and viscosity of the emulsions are characterized and the ability of the emulsions to release ALA following in vitro application is tested. The delivery systems are administered intravesically for 1 and 3 h in rats to examine the drug accumulation in bladder tissue.

Permeation enhancer-containing water-in-oil nanoemulsions as carriers for intravesical cisplatin delivery.

Purpose: In the present work, we developed water-in-oil (w/o) nanoemulsions for the intravesical administration of cisplatin.

Methods: The nanoemulsions were made up of soybean oil as the oil phase and Span 80, Tween 80, or Brij 98 as the emulsifier system. alpha-Terpineol and oleic acid were incorporated as permeation enhancers.