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A colorimetric probe N,N’-bis(2-methoxy-ethyl)-2,3,3-trimethyl-3H-squaraine (MOESQ) with H2O solubility was synthesized to detect Cu2+. MOESQ exhibits good selectivity, high sensitivity and fast UV-Vis response toward Cu2+ over other competing ions in CH3CN. The detection limit of MOESQ for Cu2+ in CH3CN can reach 1.88 × 10−7 molL−1. By adsorbing MOESQ on the chromatography paper, a colorimetric test paper for Cu2+ was prepared, which could detect Cu2+ with the color change from blue to faint yellow even in the limit of detection concentration of 10−6 molL−1.

Excess tosyl chloride used in the tosylation of alcohols is quickly and easily removed by reacting it with cellulosic materials, e.g., filter paper, and filtering.

A novel 1,2-indanedione-based bi-functional reagent was designed for the development of latent fingerprints on paper substrates. The reagent was synthesized using a concise five-step protocol and applied using a modified multi-metal deposition (MMD) process. Positive images of latent fingerprints were developed showing preferential binding to the fingerprint ridges. Fingerprints that contain both amino acids as well as oily substances were successfully detected supporting the reagent’s efficiency.

Paraformaldehyde was employed as a hydride source in the palladium-catalyzed hydrodehalogenation of aryl iodides and bromides. High throughput screening using a paper-based colorimetric iodide sensor (PBCIS) showed that Pd(OAc)2 and Cs2CO3 were the best catalyst and base, respectively. Aryl iodides and bromides were hydrodehalogenated to produce the reduced arenes using Pd(OAc)2 and Pd(PPh3)4 catalyst. This catalytic system showed good functional group tolerance. In addition, it was found that paraformaldehyde is the hydride source and the reducing agent for the formation of palladium nanoparticles.

An efficient AcO− sensor L which contains 1,10-phenanthroline-based and nitrophenylhydrazine-based groups, and its water-soluble Ru(II) complex were synthesized, characterized and studied in this Letter. Via UV–vis experiments and 1H NMR titration in DMSO solution, it was found that there were potential hydrogen bonds between the N CH and AcO− after the deprotanation of two –NH during the reaction of L or its Ru complex with anions. Furthermore, an easy-to-prepare test paper was developed to detect AcO− at 10 mg/L in pure aqueous solution.

Irradiation of tetrahydrofuran solutions of quinone methide 1 at 350 nm resulted in the formation of yellow oligomeric products and guaiacol. The rate constants determined for the disappearance of the starting compound and those of guaiacol formation show that the primary reaction involves homolysis of the C-O bond between the allylic carbon atom and the oxygen of the phenolic group. (C) 2002 Elsevier Science Ltd. All rights reserved.

Nematodes are parasitic organisms that cause significant damage to crops. Tioxazafen (Nemastrike®), is a proprietary seed treatment being developed by Bayer AG as a broad-spectrum nematicide. Thiophene-2-carbonyl chloride (TCC) is the key raw material in the manufacture of tioxazafen. Current manufacturing routes to TCC suffer from byproduct formation and significant waste generation, which leads to high manufacturing cost. A potentially more cost-effective process for preparing TCC from commercial thiophene has been developed. The advantages of this new chemical approach are illustrated in the processing details described in this Letter.

All claims in the paper cited (Tetrahedron Lett. 3249 (1979)) should be accepted as fact after, but not before, verification by independent experiment.

This Letter aimed to develop an efficient method for the determination of cyanide ion (CN − ). A novel colorimetric chemosensor 4-[(1 E )-2-(4-hydroxyphenyl)ethenyl]-1-allylpyridinium bromide (HPEAPB) was synthesized. HPEAPB displayed good selectivity toward CN − over other competing anions in ethanol. A color change from yellow to red was immediately observed upon the addition of CN − and the limit of detection (LOD) was 3.4 × 10 −6 mol L −1 . The sensing mechanism was discussed by UV–vis, 1 H NMR titration, and a comparison study. Colorimetric test paper for CN − was prepared by attaching HPEAPB to a chromatography paper, which could be used to detect CN − in environmental samples as simply as a pH-indicator paper for pH value. The LOD of the test paper for CN − was 2.0 × 10 −4 mol L −1 . This detection method for CN − has potential applications in cyanide ion containing fields by combination of rapid and real-time advantages.

A new chemosensor based on pyrylium salt has been developed. The sensor can selectively fulfill the detection of lysine among 20 common amino acids in aqueous environment and exhibit a distinct color change and ‘turn-on’ fluorescence. Besides, simple test paper based on this sensor was also presented, which elucidated the feasibility of lysine detection in real samples.

For the first time, we have successfully performed the Henry reaction in neat ‘ Natural Feedstock Extract ’ at room temperature. Herein, we used two most abundant natural feedstock extracts such as ‘ Water Extract of Banana ’ (WEB) and ‘ Water Extract of Rice Straw Ash ’ (WERSA). This protocol is highly advantageous owing to the employment of natural feedstock as green reaction media resulting in significant novelty and advancement with respect to green and sustainable chemistry.

Rhodamine hydrazide-based chemosensors that can detect volatile acidic gases in solid state have been developed. The rhodamine hydrazide probes adsorbed on filter paper respond fluorescently and colorimetrically only to volatile acidic gases but not to organic bases nor to other volatile organic compounds (VOCs). Diethyl chlorophosphate (DCP), one of model compounds used for the studies of Chemical Warfare Agent (CWA), could also be detected by using this method.

In order to establish the tosylated positions of α- and β-cyclodextrins, 13 C-nmr spectra for the monotosyl-derivatives prepared in an alkaline aqueous solution were examined and determined to be in the 6-position of one glucose unit for β-cyclodextrin and to be in the C-2 position for α-cyclodextrin.

As one of the important industrial chemicals, hydrazine (N 2 H 4 ) can be inhaled through the skin, leading to many serious health issues. In this paper, we constructed a novel turn-on fluorescent probe HBTM for N 2 H 4 detection based on ESIPT and ICT mechanism by incorporating the methyl dicyanvinyl group to 2-(2′-hydroxylphenyl) benzothiazole (HBT) fluorophore. The probe showed the following advantages: high sensitivity with detection limit of 2.9 × 10 −7 M, high selectivity over other related interfering species, wide linear range of 0–140 μM and pH value adaptation. Moreover, the probe could detect N 2 H 4 on paper strips and image N 2 H 4 in living cells.

This article has been retracted at the request of the Editor-in-Chief and Authors. Please see Elsevier Policy on Article Withdrawal ( http://www.elsevier.com/locate/withdrawalpolicy ). Reason: The Editors and Publisher would like to confirm the retraction of this paper at the request of the Authors. This work outlined in this article was a duplication of papers that had already appeared in Mehta et al. ( Indian J. Chem. , 31B (1992) 473–482) and Marchand et al. ( Synth. Commun. , 28 (1998) 541–546) and also by Chou et al. ( J. Chin. Chem. Soc. , 51 (2004) 167–174). The authors would like to apologize for this error on their part.

In this paper, a pybox-copper catalyzed enantioselective decarboxylative [4+2] cycloaddition reaction of ethynyl benzoxazinanones with azlactones has been developed, which provides optically active 3,4-dihydroquinolin-2-ones in high yields with good enantioselectivities and diastereoselectivities. In this transformation, the chiral dipolar copper–allenylidene intermediates are kinetically generated via decarboxylative ethynyl benzoxazinanones, followed by the attack of the enolate azlactones to form enantiomerically enriched 3,4-dihydroquinolin-2-one structures.

In this paper we have described the synthesis and coordination properties of monometallic Zinc complex of oxygen depleted bis(pyrazole)-p-tert-butylcalix[4]arene ligand. We also present the catalytic activity of the Zinc–bis(pyrazole) complex, in acetylation of alcohols and lactide polymerization.

© 2019 Elsevier Ltd Reactions of thioamides with nitrogen-rich 1,3-dipoles, diazo compounds and azides, have been known for long time already. However in recent years introduction of catalysts of different types (rhodium-, ruthenium- and copper-containing and Lewis acids) as well as highly electrophilic sulfonyl azides, allowed the development of new methods for the synthesis of heterocycles, enamines and N-sulfonyl amidines. Moreover, a new methodology in organic synthesis, based on generation and subsequent transformations of α-diazocarbonyl compounds was created. Reactions of sulfonyl azides with thioamides undergo readily in mild conditions to produce different sorts of N-sulfonyl amidines and represent a new type of click-type processes. Most of the cited works were published in the current decade. Earlier seminal papers are also reviewed when they constitute the background for new synthetic methods which were developed further. ispartof: TETRAHEDRON LETTERS vol:60 issue:7 pages:513-523 status: published

Benzoquinone ansamycins are known to be potent Heat shock protein (Hsp90) inhibitors, and total-synthesis-based structure modification of this natural product family may lead to the discovery of novel cancer chemotherapeutics. Described in this paper is a unified synthetic route that gives access to both natural and C-8-modified C5-C15 fragments of this natural product family.

In this paper, we have described a simple and efficient strategy for the synthesis of fused pyrazole derivatives. The key steps of our strategy involves hydroamination, copper-catalyzed cross dehydrogenative coupling (CDC) followed by aromatization (aerial oxidation) in one-pot. Our strategy offers a valuable alternative to known methods for synthesis of fused pyrazole derivatives. Overall, we have synthesized 13 diverse fused pyrazole derivatives in moderate to excellent yields.

A general approach for a collective synthesis of natural products containing substituted THF ring is described. In this paper, Arbusculone, a small molecule natural product accomplished using a short route, is used as the key intermediate to achieve the total synthesis of Andirolactone, Pinnatolide, Ipomolactone, Cyclocapitelline, Isocyclocapitelline and their two isomers in less than ten steps. The present effort highlights protecting-group-free total syntheses and the shortest route to access these natural products from commercially available cheap starting materials.

Direct catalytic asymmetric vinylogous reaction serves as a powerful tool to introduce stereocenter(s) at the γ- or/and even more remote position(s) of the vinylogous products in an atom-economical and efficient way. A variety of direct catalytic asymmetric vinylogous reactions with broad substrate scope and mild reaction conditions has been developed. Both metal catalysis and organocatalysis contributed in this field and led to the vinylogous products in high stereoselectivity. These vinylogous reactions provided efficient pathways for the synthesis of highly functionalized optically pure compounds, especially these with potential biological activity and pharmacological activity. This digest paper mainly focuses on the most recent developments in this field, including both nucleophilic addition and nucleophilic substitution.

Copper(I) catalyzed radical benzylation and cyclization reaction of tertiary enamides was investigated and 3,3-disubstituted N-Alkyl isoindolin-1-ones were obtained in moderate to good yields. In this reaction, two new C–C bonds were formed in one step with high atom economy. Possible reaction pathway for the formation of the products was also discussed in this paper.

This paper describes the use of poly(α -olefin)s (PAOs) as safer alternatives to cyclohexane, hexanes, and heptane as solvents for alkyllithium reagents. While PAOs like any alkane are flammable, PAOs do not readily catch on fire because they contain 20 or more carbon atoms, a low volatility, and have a high flash point vis-a-vis alkanes like hexane. Also unlike conventional alkanes, PAOs can be quantitatively separated from polar organic solvents and polar organic products either by a simple gravity separation or by an extraction after a reaction. Any leaching of the PAO solvent into a polar phase during such a separation can be minimized by addition of small amounts of water to the polar phase. However, while these PAO solvents have some physical differences from conventional low molecular weight volatile alkanes, they otherwise behave like alkanes and alkyllithium reagents in these PAO solvents can used in their conventional reactions in these PAO solvents.

Sulfoxide-promoted ortho-C–H functionalization reactions of aromatic compounds have emerged as powerful tools for organic synthesis. Among them, [3,3] sigmatropic rearrangement induced by interrupted Pummerer reaction or electrophilic activation of sulfoxides has proved to be a fruitful strategy due to its versatility and high reaction efficiency. This digest paper mainly focuses on recent progress on C–H functionalization reactions of aryl sulfoxides via [3,3] sigmatropic rearrangement of sulfonium-tethered intermediates.

In this paper, a Rh(III)-catalyzed cascade reaction of benzoyl acetonitriles/methylsulfones (1) with cyclic 2-diazo-1,3-dicarbonyl compounds (2) leading to a convenient and efficient preparation of diversely functionalized naphtho[1,8-bc]pyrans is presented. Mechanistically, the formation of the title compounds involves a cascade process including: 1) C(sp2) H/C(sp3) H bonds cleavage, metalation and carbeniod insertion of 1 with 2 followed by an intramolecular annulation to afford substituted 1-naphthol as a key intermediate; 2) C(sp2) H/O H bonds cleavage, metalation and carbeniod insertion of the in situ formed 1-naphthol intermediate with 2 followed by an intramolecular cyclization to give the naphtho[1,8-bc]pyran product. Compared with literature methods for the synthesis of naphtho[1,8-bc]pyran derivatives, this new protocol has advantages such as simple operational procedure, easily obtainable substrates, high efficiency and excellent atom-economy.

The development of rapid and simple approaches for detection of G-quadruplex DNA structures has attracted significant attention to disclose their diverse physiological and pathological functions. Thiazole orange (TO) is a common fluorescence probe used for the detection of G-quadruplexes. However, it still suffers from some common problems like non-selective for G-quadruplex and emission in the lower wavelength region of spectrum, thus hampering its further applications. Probes with turn-on fluorescence in the far-red region are highly sought-after due to minimal auto-fluorescence and cellular damage. In this paper, we described a far-red fluorescent probe (L-1) by introducing an amine group into styrylquinolinium scaffold. The experimental results indicated that L-1 exhibited significant fluorescence enhancement when treated with G-quadruplexes but retained weak fluorescence in the presence of duplex DNAs. In addition, this probe also displayed higher binding affinity for parallel G-quadruplexes. The characteristics of L-1 were further investigated with UV–vis spectrophotometry, fluorescence, circular dichroism, KI quenching, FID assay and molecular docking to validate optical photophysical properties, as well as the selectivity, sensitivity and detailed binding mode toward G-quadruplex DNAs.

Cryptands, seen as a kind of crown ether derivatives, have attracted much attention because of their three dimensional spatial structures and additional binding sites. Moreover, by changing functional groups on the third arm, various stimuli-responsive host–guest systems were obtained, which have played key roles in the construction of functional supramolecular systems. The recent advances in supramolecular systems constructed by crown ether-based cryptands, and further applications, especially in supramolecular polymers are summarized in this digest paper.

In this Digest paper, various approaches toward chemical synthesis of negamycin, a natural dipeptide-like antibiotic, were summarized. The strategy and tactics in each individual synthesis were highlighted. Although the chemical structure of negamycin is relatively simple, the promising bioactivity against Gram-negative bacteria with a novel mechanism of action renders it as an intriguing lead compound for medicinal development.

In this paper, we describe our efforts toward the asymmetric synthesis of Daphniphyllum alkaloid 21-deoxymacropodumine D which led to efficient preparation of a ABC tricyclic framework containing five consecutive stereocenters. This synthetic work features (1) utilization of an asymmetric conjugate addition to install the C5 all-carbon quaternary center, (2) an intramolecular aza-Michael addition followed by Pd-catalyzed α-alkenylation to build the bowl-shaped tricyclic core.

The 1,3-dithian-2-yl-methyl (Dim) and its analogous groups including dimethyl-Dim (dM-Dim) can provide a new dimension of orthogonality for carboxylic acid protection. They can be deprotected under nearly neutral oxidative conditions. In this paper, the protection of carboxylic acid with dM-Dim, deprotection of dM-Dim ester with sodium periodate, stability of dM-Dim protected carboxylic acid under acidic and basic conditions, and selective deprotection of dM-Dim protected carboxylic acids in the presence of tertiary butyl and methyl esters are presented.

The deoxygenation of tertiary and secondary alcohols to give the corresponding alkanes is conventionally performed using an organosilane and a strong acid. In this study, a deoxygenation method was developed for tertiary and secondary alcohols, using trimethylsilane and trimethylsilyl iodide generated in situ from sodium borohydride and trimethylsilyl chloride, and trimethylsilyl chloride and potassium iodide, respectively. With our method, tertiary and secondary alcohols, which provided stable carbocations, were converted into the corresponding alkanes. This paper also presents the optimization of the reaction conditions, the reaction mechanism, as well as the scope and limitations of the method.

As a rigid and planar aza-based heteroaromatic scaffold, hexaazatriphenylene (HAT) exhibits excellent electron-deficient property and high π-π stacking tendency, which makes it an ideal building block in the construction of supramolecular architectures and functional materials. In addition, HATs have also been picked out as building blocks for the construction of novel porous organic polymers, one of the most attractive fields of porous materials in the past decade, which includes intrinsic microporosity (PIMs), π-conjugated microporous polymers (CMPs), and covalent organic frameworks (COFs). In this digest paper, the synthetic methods of HAT derivatives have been briefly introduced and some recent advances of HATs in the applications of supramolecular self-assembly and porous organic materials have been highlighted.

Transfer hydrogenation using inexpensive and safe hydrogen sources of alcohols and formic acid has been studied thoroughly over the decades. In particular, the asymmetric version offers the state-of-the-art methods to obtain optically active alcohols and amines, which are valuable synthetic intermediates in the field of pharmaceutical and agrochemical industry. This digest paper highlights the recent notable advances in homogeneous transfer hydrogenation using transition metal complexes, especially in direction to establish practical greener processes by upgrading the catalyst performance or by expanding the scope of reducible functional groups.