Prediction of ammonia contaminants in the aquaculture ponds using soft computing coupled with wavelet analysis.

Intensive aquaculture practices generate highly polluted organic effluents such as biological oxygen demand (BOD), alkalinity, total ammonia, nitrates, calcium, potassium, sodium, iron, and chlorides. In recent years, Inland aquaculture ponds in the western delta region of Andhra Pradesh have been intensively expanding and are more concerned about negative environmental impact. This paper presents the water quality analysis of aquaculture waters in 64 random locations in the western delta region of Andhra Pradesh. The average water quality index (WQI) was 126, with WQI values ranging from 21 to 456. Approximately 78% of the water samples were very poor and unsafe for drinking and domestic usage. The mean ammonia content in aquaculture water was 0.15 mg/L, and 78% of the samples were above the acceptable limit set by the World Health Organization (WHO) of 0.5 mg/L. The quantity of ammonia in the water ranged from 0.05 to 2.8 mg/L. The results show that ammonia levels exceed the permissible limits and are a significant concern in aquaculture waters due to toxicity. This paper also presents an intelligent soft computing approach to predicting ammonia levels in aquaculture ponds, using two novel approaches, such as the pelican optimization algorithm (POA) and POA coupled with discrete wavelet analysis (DWT-POA). The modified and enhanced POA with DWT can converge to higher performance when compared to standard POA, with an average percentage error of 1.964 and a coefficient of determination (R2) value of 0.822. Moreover, it was found that prediction models were reliable with good accuracy and simple to execute. Furthermore, these prediction models could help stakeholders and policymakers to make a real-time prediction of ammonia levels in intensive farming inland aquaculture ponds.

Transition-metal-free Chemoselective Oxidative C-C Coupling of the sp3 C-H Bond of Oxindoles with Arenes and Addition to Alkene: Synthesis of 3-Aryl Oxindoles, and Benzofuro- and Indoloindoles.

A transition-metal (TM)-free and halogen-free NaOtBu-mediated oxidative cross-coupling between the sp3 C-H bond of oxindoles and sp2 C-H bond of nitroarenes has been developed to access 3-aryl substituted and 3,3-aryldisubstituted oxindoles in DMSO at room temperature in a short time. Interestingly, the sp3 C-H bond of oxindoles could also react with styrene under TM-free conditions for the practical synthesis of quaternary 3,3-disubstituted oxindoles. The synthesized 3-oxindoles have also been further transformed into advanced heterocycles, that is, benzofuroindoles, indoloindoles, and substituted indoles. Mechanistic experiments of the reaction suggests the formation of an anion intermediate from the sp3 C-H bond of oxindole by tert-butoxide base in DMSO. The addition of nitrobenzene to the in-situ generated carbanion leads to the 3-(nitrophenyl)oxindolyl carbanion in DMSO which is subsequently oxidized to 3-(nitro-aryl) oxindole by DMSO.

Transition-Metal-Free Selective Oxidative C(sp3)-S/Se Coupling of Oxindoles, Tetralone, and Arylacetamides: Synthesis of Unsymmetrical Organochalcogenides.

Transition-metal-free synthetic methods have been developed for the preparation of unsymmetrical diaryl and aryl alkyl chalcogenides: sulfones, sulfides, and selenides from the sp3-C-H bond of oxindole, tetralone, arylacetamide, and aryl chalcogenide precursors. Sulfones were obtained from sodium sulfinates using potassium iodide, tert-butyl hydroperoxide in DMSO, and acetic acid. Sulfides and selenides were prepared from diaryl disulfides or diselenides employing potassium tert-butoxide in DMSO. α-Tetralone underwent concomitant chalcogenation and aromatization resulting in 2-chalcogenyl-1-naphthols in one pot.

Organoselenium and DMAP co-catalysis: regioselective synthesis of medium-sized halolactones and bromooxepanes from unactivated alkenes.

A catalytic system consisting of bis(4-methoxyphenyl)selenide and 4-(dimethylamino)pyridine (DMAP) has been developed for the regioselective synthesis of medium-sized bromo/iodo lactones and bromooxepanes possessing high transannular strain. (77)Se NMR, mass spectrometry and theoretical studies reveal that the reaction proceeds via a quaternary selenium intermediate.

KO(t)Bu-mediated aerobic transition-metal-free regioselective ß-arylation of indoles: synthesis of ß-(2-/4-nitroaryl)-indoles.

A KO(t)Bu-mediated intermolecular oxidative C-C coupling of nitroarenes with indoles is presented in DMSO at room temperature in an open flask. By using this mild and economical methodology, syntheses of ß-(2/4-nitroaryl)-indoles with sensitive functionalities such as bromo, iodo, cyano, and nitro were achieved chemo- and regioselectively. Synthesized ß-(2/4-nitroaryl) indoles were transformed into densely functionalized biindoles, indoloindoles, and (4-aminoaryl)-indoles which demonstrate post-transformation utility of the developed methodology.

Transition metal free intramolecular selective oxidative C(sp3)-N coupling: synthesis of N-aryl-isoindolinones from 2-alkylbenzamides.

A synthetic method has been developed for the preparation of biologically important isoindolinones including indoprofen and DWP205190 drugs from 2-alkylbenzamide substrates by transition metal-free intramolecular selective oxidative coupling of C(sp(3))-H and N-H bonds utilizing iodine, potassium carbonate and di-tert-butyl peroxide in acetonitrile at 110-140 °C.

Chemoselective arylation of phenols with bromo-nitroarenes: synthesis of nitro-biaryl-ols and their conversion into benzofurans and carbazoles.

A series of electron withdrawing or donating group substituted phenols were chemoselectively arylated with various substituted bromo-nitroarenes using KO(t)Bu at room temperature via an SNAr pathway. The synthesis of natural alkaloids (carbazoles), dibenzofurans, and a biaryl-indole was achieved from the synthesized nitro-biaryl-ols.

Metal free sulfenylation and bis-sulfenylation of indoles: persulfate mediated synthesis.

A method which avoids metal and halogen for the synthesis of 3-arylthioindoles from indoles and diaryl disulfides using ammonium persulfate in methanol has been presented. Moreover, double C-H sulfenylation of indoles at 2 and 3-positions has also been achieved using iodine and ammonium persulfate.

Transition-metal-free synthesis of unsymmetrical diaryl chalcogenides from arenes and diaryl dichalcogenides.

A transition-metal-free synthetic method has been developed for the synthesis of unsymmetrical diaryl chalcogenides (S, Se, and Te) from diaryl dichalcogenides and arenes under oxidative conditions by using potassium persulfate at room temperature. Variously substituted arenes such as anisole, thioanisole, diphenyl ether, phenol, naphthol, di- and trimethoxy benzenes, xylene, mesitylene, N,N-dimethylaniline, bromine-substituted arenes, naphthalene, and diaryl dichalcogenides underwent carbon-chalcogen bond-forming reaction to give unsymmetrical diaryl chalcogenides in trifluoroacetic acid. To understand the mechanistic part of the reaction, a detailed in situ characterization of the intermediates has been carried out by (77)Se NMR spectroscopy by using diphenyl diselenide as the substrate. (77)Se NMR study suggests that electrophilic species ArE(+) is generated by the reaction of diaryl dichalcogenide with persulfate in trifluoroacetic acid. The electrophilic attack of arylchalcogenium ion on the arene may be responsible for the formation of the aryl-chalcogen bond.

Isoselenazolones as catalysts for the activation of bromine: bromolactonization of alkenoic acids and oxidation of alcohols.

Isoselenazolones were synthesized by a copper-catalyzed Se-N bond forming reaction between 2-halobenzamides and selenium powder. The catalytic activity of the various isoselenazolones was studied in the bromolactonization of pent-4-enoic acid. Isoselenazolone 9 was studied as a catalyst in several reactions: the bromolactonization of a series of alkenoic acids with bromine or N-bromosuccinimide (NBS) in the presence of potassium carbonate as base, the bromoesterification of a series of alkenes using NBS and a variety of carboxylic acids, and the oxidation of secondary alcohols to ketones using bromine as an oxidizing reagent. Mechanistic details of the isoselenazolone-catalyzed bromination reaction were revealed by (77)Se NMR spectroscopic and ES-MS studies. The oxidative addition of bromine to the isoselenazolone gives the isoselenazolone(IV) dibromide, which could be responsible for the activation of bromine under the reaction conditions. Steric effects from an N-phenylethyl group on the amide of the isoselenazolone and electron-withdrawing fluoro substituents on the benzo fused-ring of the isoselenazolone appear to enhance the stability of the isoselenazolone as a catalyst for the bromination reaction.