Aromatic polyamide thin-film composite membranes are widely used in reverse osmosis (RO) and nanofiltration (NF) due to their high water permeability selectivity. However, these undergo biofouling can degrade eventually fail during free chlorine exposure. To better understand this effect, the reactivity of monomer (benzanilide (BA)) with was tested under varying pH chloride (Cl-) conditions. The kinetic results indicated that current existing mechanisms, especially Orton rearrangement, were...

A tandem ketene-trapping/Diels−Alder cyclization sequence was the pivotal transformation in an efficient, asymmetric synthesis of a decahydrofluorene tricyclic structure possessing eight stereogenic centers and key features hirsutellone class antitubercular natural products. The hirsutellone-like β-keto ester that fashioned by this (13 steps; 6% overall yield) demonstrated significant inhibitory activity against Mycobacterium tuberculosis. mechanism action compound is not yet known.

Although Cl2 and Cl2O have been recognized as highly reactive constituents of free available chlorine (FAC), robust rate constants for remain scarce in the environmental literature. In this work, we explored chlorination kinetics three structurally related alkenes (α-ionone, β-ionone, dehydro-β-ionone), a class compounds whose reactivities with not previously investigated. Second-order Cl2, Cl2O, HOCl were computed from experimental obtained at various pH values, [Cl–], [FAC]. Our results...

1,3,5-Trimethoxybenzene can be used to quench residual chlorine and bromine without altering disinfection byproducts that are reactive toward traditional quenchers.

Parabens and salicylates were examined as disinfection byproduct (DBP) precursors to explore the possible influence of ipso substitution (i.e., halogen exchange) on yield speciation trihalomethanes (THMs) formed during water chlorination. Substoichiometric conversion C-Br bonds into C-Cl was confirmed for several parabens salicylates. The co-occurrence (mono)brominated nonhalogenated in presence free chlorine (but absence added Br-) generated polybrominated THMs, implicating substitution....

This account describes a strategy for directly forming three of the six rings found in polyketide natural product hirsutellone B via novel cyclization cascade. The key step our approach comprises two transformations: large-ring-forming, nucleophilic capture transient acylketene and an intramolecular Diels–Alder reaction, both which occur tandem through thermolyses appropriately functionalized, polyunsaturated dioxinones. These thermally induced "double cyclization" cascades generate new...

Chloroacetanilide herbicides are used worldwide to control weeds that affect crops such as corn, soybeans, and cotton. These frequently paired with a "safener," which prevents herbicidal damage the crop without diminishing weed control. Formulated herbicide products include safeners other ingredients infrequently assessed for toxicity. Our goal was understand potential toxicity of + safener formulations relative associated active ingredients. We quantified concentration in commercially...

Free chlorine and free bromine (<italic>e.g.</italic>, HOCl HOBr) are employed as disinfectants in a variety of aqueous systems, including drinking water, wastewater, ballast recreational waters, cleaning products.

Aromatic polyamide-based membranes are widely used for reverse osmosis (RO) and nanofiltration (NF) treatment but degrade when exposed to free chlorine (HOCl/OCl-). The reaction mechanisms with were previously explored, less is known about the role of bromide (Br-) in these processes. Br- may impact reactions by reacting HOCl form HOBr, which then triggers other brominating agents (Br2O, Br2, BrOCl, BrCl) form. This study examined reactivities a polyamide monomer model compound, benzanilide...

The first total syntheses of the natural products pyrophen and campyrones A–C, isolated from fungus Aspergillus niger, have been achieved in six steps starting commercially available N-Boc amino acids. Key this sequence include a vinylogous Claisen condensation to achieve fragment coupling dioxinone thermolysis/cyclization cascade form α-pyrone ring. route described herein afforded 15–25% overall yield, furnishing sufficient material for testing biological assays.

The mulinane class of diterpenoids is a set tricyclic (5-6-7), biologically active natural products whose members exhibit variety oxidation states. Herein, we report the inaugural synthesis four mulinanes employing divergent approach that relies on diastereoselective anionic oxy-Cope rearrangement to relative configuration C8 stereocenter and an unprecedented vinylogous Saegusa dehydrogenation reaction address C-ring functionality.

A synthesis of the proposed structure lineariifolianone has been achieved in eight steps and 9% overall yield starting from (+)-valencene, leading to a reassignment absolute configuration this unusual cyclopropenone-containing natural product. Key synthetic route include kinetic protonation an enolate epimerize C7 stereocenter stereoconvergent epoxide opening establish trans-diaxial diol functionality. The syntheses enantiomers two other closely related products are also reported, confirming...

Safeners are used extensively in commercial herbicide formulations. Although safeners regulated as inert ingredients, some of their transformation products have enhanced biological activity. Here, to fill gaps our understanding safener environmental fate, we determined rate constants and associated with the acid- base-mediated hydrolysis dichloroacetamide AD-67, benoxacor, dichlormid, furilazole. Second-order for (HCl) (NaOH) (2.8 × 10–3 0.46 0.3–500 M–1 h–1, respectively) were, many cases...

Organic compounds containing the tricarbonylmethane functional group occupy a unique place in organic chemistry (Figure 1). As C-acylated derivatives of more familiar 1,3-dicarbonyls, tricarbon...

The first total synthesis of the novel cyclohexylethanoid natural product clerobungin A has been achieved in six steps and 14% overall yield starting from commercially available tyrosol. Key this sequence include a bioinspired oxidative dearomatization phenol hemiacetalization/oxa-Michael cascade to form tricyclic ring system. Resolution late-stage intermediate via chiral HPLC allowed for measurement chiroptical properties both enantiomers A, supporting scalemic nature product.

Electrophilic aromatic substitution reactions can initiate halogenated disinfection byproduct (DBP) formation. The rate-controlling step (RCS) of electrophilic halogenation is commonly assumed to be halogen addition (vs proton removal), although this assumption has not been previously assessed under water conditions. Herein, the herbicide dimethenamid (DM) was used as a model compound examine RCS in treated with free chlorine (chlorination), and bromide (bromination), or monochloramine...

Dichloroacetamide safeners are common ingredients in commercial herbicide formulations. We previously investigated the environmental fate of dichloroacetamides via photolysis and hydrolysis, but other potentially important, environmentally relevant processes remain uncharacterized may yield products concern. Here, we examined microbial biotransformation two dichloroacetamide safeners, benoxacor dichlormid, to identify elucidate pathways. Using aerobic microcosms inoculated with river...

A convergent synthetic route to the fungal metabolites cladosins B and C has been developed, affording these natural products in 29% 27% overall yield, respectively. The are rare examples of hybrid polyketides featuring a 3-enamine tetramic acid group derived from l-valine. Key steps this modular six-step sequence include DMAP-mediated O- C-acyl rearrangement unite side chains with core subsequent amine incorporation using either ammonium acetate or HMDS.

Abstract The enantioselective total synthesis of the alkaloid aristoquinoline has been achieved in seven steps and 26% overall yield. A new preparation useful synthetic building block (–)-α-terpinyl amine was also developed order to avoid stoichiometric mercury reagents or azide-containing intermediates. Key optimized route include an intramolecular nitrilium ion cyclization form characteristic azabicyclo[3.3.1]nonane ring system a dia­stereoselective reduction resulting imine mixture afford...