Constructing spirooxindoles from non-oxindole precursors: a one-pot nitro-reduction/double lactamization approach to spiro[indoline-3,3'-quinoline]-2,2'-diones.

2-(2-Nitrobenzyl)-2-(2-nitrophenyl)malonates, readily prepared by SAr-arylation of diethyl malonate with -fluoronitrobenzenes, followed by S2-alkylatioin of the resulting products with -nitrobenzyl bromides, undergo a tandem Fe/AcOH-promoted nitro-reduction and double lactamization sequence to afford spiro[indoline-3,3'-quinoline]-2,2'-diones in high overall yields. The method is operationally simple, economical, and has a broad substrate scope. The synthetic practicality of this methodology was illustrated by performing the reaction on a gram scale with the same efficiency.

Reduction-enhanced water flux through layered graphene oxide (GO) membranes stabilized with HO and OH ions.

Graphene oxide (GO) is one of the most promising candidates for next generation of atomically thin membranes. Nevertheless, one of the major issues for real world application of GO membranes is their undesirable swelling in an aqueous environment. Recently, we demonstrated that generation of HO and OH ions (, with an external electric field) in the interlayer gallery could impart aqueous stability to the layered GO membranes (A.

Synthesis of benzimidazole-fused 1,4-benzoxazepines and benzosultams spiro-connected to a 2-oxindole core a tandem epoxide-opening/SAr approach.

While hundreds of literature reports describe the preparation of spirooxindole-based five- and six-membered heterocycles, the construction of seven-membered heterocyclic rings spiro-connected to a 2-oxindole core has so far been less developed. Herein, we disclose a base-mediated (4 + 3) annulation of spiro-epoxyoxindoles and 2-(2-fluoroaryl)-1-benzoimidazoles or 2-fluoro--arylbenzenesulfonamides toward the synthesis of two new classes of spirooxindole-based polycyclic systems. Mechanistically, this conceptually simple and high atom-economical reaction proceeds an S2-like intermolecular epoxide ring-opening, accompanied by a concomitant intramolecular SAr reaction.

An epoxide-opening cyclization/double Smiles rearrangement cascade approach to -aryl-1,4-benzoxazines and -arylindolines.

Reported herein is a transition-metal-free protocol for a regio- and diastereoselective synthesis of hydroxyalkyl group-embedded -arylbenzo[][1,4]oxazines and -arylindolines based on an epoxide-opening cyclization/double Smiles rearrangement cascade of -nosylamide-tethered epoxides. To the best of our knowledge, this is the first report of the integration of epoxide-opening cyclization with Smiles rearrangement in a cascade fashion, enabling simultaneous construction and -arylation of N-heterocycles. The reaction employs substrates derived from commercially available 2-nitrophenols and easily accessible allylic halides/alcohols, and exhibits a broad substrate scope and delivers the products in high yields.

Arresting Aqueous Swelling of Layered Graphene-Oxide Membranes with HO and OH Ions.

Over the past decade, graphene oxide (GO) has emerged as a promising membrane material with superior separation performance and intriguing mechanical/chemical stability. However, its practical implementation remains very challenging primarily because of its undesirable swelling in an aqueous environment. Here, we demonstrated that dissociation of water molecules into HO and OH ions inside the interlayer gallery of a layered GO membrane can strongly affect its stability and performance.

Effect of an ionic environment on membrane fouling: a molecular dynamics study.

The effect of the ionic environment on membrane fouling was investigated for polyamide (PA) and graphene oxide (GO) membranes using equilibrium molecular dynamics (MD) simulations. For each of these membranes, bovine serum albumin (BSA) was considered as the model foulant. The effect of the foulant on the membranes is investigated at seawater concentration and also in a normal aqueous environment.

Influence of the presence of cations on the water and salt dynamics inside layered graphene oxide (GO) membranes.

Although over the past few years, graphene oxide (GO) has emerged as a promising membrane material, the applicability of layered GO membranes in water purification/seawater desalination is still a challenging issue because of the undesirable swelling of GO laminates in the aqueous environment. One of the ways to tune the interlayer spacing and to arrest the undesirable swelling of layered GO membranes in the aqueous environment is to intercalate the interlayer spacing of the GO laminates with cations. Although the cation intercalation imparts stabilization to GO laminates in the aqueous environment, their effect on the performance of the membrane is yet to be addressed in detail.

Climate Change, Health and Mosquito-Borne Diseases: Trends and Implications to the Pacific Region.

Climate change is known to affect Pacific Island nations in a variety of ways. One of them is by increasing the vulnerability of human health induced by various climate change impacts, which pose an additional burden to the already distressed health systems in the region. This paper explores the associations between climate change and human health on the one hand, and outlines some of the health care challenges posed by a changing climate on the other.

What governs the nature of fouling in forward osmosis (FO) and reverse osmosis (RO)? A molecular dynamics study.

Membrane fouling is a performance hampering phenomenon, which impacts forward osmosis (FO) and reverse osmosis (RO) differently. Experiments have found that the fouling layer structure for FO and RO is very different, but the reasons are not yet very clear, and hence a mechanistic understanding of the fouling in FO and RO is indispensable. Here we used molecular dynamics (MD) simulations to characterize the nature of fouling in FO and RO.

Effect of graphene oxide (GO) nanosheet sizes, pinhole defects and non-ideal lamellar stacking on the performance of layered GO membranes: an atomistic investigation.

The effect of non-idealities, namely pinhole defects and non-ideal lamellar stacking of nanosheets, on the performance of size-differentiated graphene oxide (GO) laminates is investigated using equilibrium molecular dynamics (MD) simulations. With the increase in sizes of the constituent GO nanosheets the water permeability of the layered GO membranes decreases and salt rejection increases. But with the inclusion of non-idealities the difference in water permeability between these membranes substantially reduced.

Aggregation-Induced Emission Active Metal-Free Chemosensing Platform for Highly Selective Turn-On Sensing and Bioimaging of Pyrophosphate Anion.

We report the synthesis of a metal-free chemosensor for highly selective sensing of pyrophosphate (PPi) anion in physiological medium. The novel phenylbenzimidazole functionalized imine containing chemosensor (L; [2,6-bis(((4-(1H-benzo[d]imidazol-2-yl)phenyl)imino) methyl)-4 methyl phenol]) could sense PPi anion through "turn-on" colorimetric and fluorimetric responses in a very competitive environment. The overall sensing mechanism is based on the aggregation-induced emission (AIE) phenomenon.

Anion complexation with cyanobenzoyl substituted first and second generation tripodal amide receptors: crystal structure and solution studies.

Anion complexation properties of two new tripodal amide receptors have been extensively studied here. Two tripodal receptors have been synthesized from the reaction of cyanobenzoyl acid chloride with two tri-amine building blocks such as (i) tris(2-aminoethyl)amine and (ii) tris(2-(4-aminophenoxy)ethyl)amine, which resulted in the first (L1) and second (L2) generation tripodal amides respectively. A detailed comparison of their coordination behavior with anions is also described by crystallographic and solution state experiments.