1,721,046 research outputs found
MODELING PROPERTIES AND REACTIVITY OF QUINONE METHIDES BY DFT CALCULATIONS
No full textA review on the properties and reactivity of Quinone Methides as alkylating agents modelled in silico by density functional theor
Hydrosoluble and solvatochromic naphthalene diimides with NIR absorption
No full textMimicking biochromophore anions containing phenolate moieties, eight conjugated naphthalene diimides (NDIs) have been synthesized in order to develop probes, displaying charge-transfer transitions affected by the nearby environment. NIR absorption of the resulting phenolates and their solvatochromic properties in both organic solvents and water are described
Vinylidene–Quinone Methides, Photochemical Generation and β-Silicon Effect on Reactivity
No full textIrradiation of 2-alkynylphenols resulted in the
generation of vinylidene−quinone methides (QMs), which
were detected by laser flash photolysis in organic solvents and aqueous acetonitrile. QMs' spectroscopic properties and
electrophilicity were both significantly affected by β-silicon
effect. The hydration of the alkynyl moiety was an acid- and
base-catalyzed process. The addition of amines was fast, yielding ketimines, with primary amine
Quinone Methides as DNA Alkylating Agents: An Overview on Efficient Activation Protocols for Enhanced Target Selectivity
No full textThe following review analyzes the most effective activation protocols for the generation of transient electrophilic quinone methides, merged into the recent strategies to achieve recognition and alkylation of nucleic acids. The covalent targeting has to be specific for selected oligonucleotide sequences (sequence-specificity) or for those oligonucleotides capable to fold into supramolecular structures, such as G-quadruplexes (structure-specificity). The reversibility of the DNA alkylation process by QM is reviewed underlining the opportunities (in term of selectivity and delivery) and drawbacks (in term of product characterization of the covalent damage) in the DNA targeting
Selective Arylation, Alkenylation, and Cyclization of Dibromonaphthols, Using Visible Light, via Carbene Intermediates
No full textThe photoreactivity of several 3-substituted-1,6-dibromo-2-naphthols has been investigated in neat acetonitrile in the presence of diluted Et3N and in aqueous buffered acetonitrile (pH 8, phosphate buffered), using visible light (450 nm). Hydrobromic acid loss in the presence of the base, for the unsubstituted naphthol, or heterolytic C-Br cleavage directly from the naphtholates, for the more acid 3-substutited naphthols (R=COOCH3, CONH2, CONMe2), generates electrophilic carbene
intermediates, which have been successfully trapped by molecular oxygen, pyrrole, acrylonitrile, ethyl vinyl ether, and allyltrimethylsilane. Product distribution analysis reveals three types of products arising from (i) arylation, (ii) alkenylation, and (iii) cyclization reactions. The generation and the reactivity of a ketocarbene intermediates, as electrophilc diradicals, has been supported by laser flash photolysis, with the detection of both the carbene (λmax 510 nm) and 1,2-naphthoquinone-O-oxide (R=CONMe2, λmax 600 nm) in the presence of oxygen
Naphthalene diimides as selective naked-eye chemosensor for copper(II) in aqueous solution
No full textSubstituted and water-soluble naphthalene diimides (NDIs) exhibiting (CH2)2NMe2 coordinating moieties have been shown to be selective and fast responding mono- and di-nuclear colorimetric Cu(II) chemosensor
The flavonoids and oil composition of parsley [Petroselinum crispum (Mill) Nyman] fruits
No full textThe chemical composition of the volatile, fixed oil and flavonoid fraction extracted from the fruits of parsley was investigated in two cultivar and a local ecotype of the species. Nine compounds were detected in the flavonoid fraction, being glycosyl and glycosyl malonate derivatives of apigenin and chrysoeriol the most abundant. Among these, apigenin 7-O-[apiofuranosyl(1→2)-β-glucopyranoside] (apiin) counted up to 6.97 mg·g−1 on average, while the compounds apigenin 7-O-[apiofuranosyl(1→2)-(6”-O-malonyl-β-glucopyranoside)] and chrysoeriol 7-O-[apiofuranosyl(1→2)-(6”-O-malonyl-β-glucopyranoside)], accounting for 15.01 mg·g−1 and 6.52 mg·g−1, respectively, were detected for the first time in the fruits of the species. Furthermore, the complete identification of the latter compound, performed by NMR techniques, was reported for the first time. The local ecotype contains higher amounts of six out of nine flavonoids detected, this result supporting the interest for its possible valorisation. Additionally, sixteen compounds were detected in the volatile fraction, being the alkenylbenzenes apiole, myristicin and 1-allyl-2,3,4,5-tetramethoxybenzene the most abundants, accounting respectively for 45.63 %, 35.89 % and 3.97 %, on average. In the fixed oil, petroselinic (60.92 %) and linoleic acid (10.30 %) were the main fatty acids, and apiole (11.95 %) the main alkenilbenzene detected. This study, aimed at the complete identification and quantitation of different classes of metabolites, representes to date the most exhaustive report on the evaluation of bioactive compounds in parsley fruits, a particular food resource endowed with promising nourishing features
Photoarylation of Alkenes and Heteroaromatics by Dibromo-BINOLs in Aqueous Solution
No full textThe photochemistry of 6,6’-dibromo-BINOLs (BINOL=2,2’-dihydroxy-1,1’-binaphthyl) under mild conditions has been investigated in neat and aqueous acetonitrile through product distribution analysis and laser flash photolysis. Arylation and alkylation have been successfully achieved in the presence of allyltrimethylsilane, ethyl vinyl ether, pyrrole, pyridine, thiophene, benzene, and indole. Such a photoreactivity offers a metal and protecting group free synthetic protocol toward mono- and disubstituted 6-aryl/alkyl BINOLs, since the BINOL chirality is preserved in the photoactivation process
Photoarylation/Alkylation of Bromo-Naphthols
No full textThe photochemistry of 6-bromo-2-naphthols has been studied in acetonitrile, aqueous acetonitrile, and isopropyl alcohol in the absence and in the presence of triethylamine by product distribution analysis, laser flash photolysis (LFP), fluorescence, phosphorescence, electrochemical measurements, and DFT calculations. Hydrobromic acid loss in the presence of Et3N occurs from the triplet state of 6-bromo-2-naphthol, generating an electrophilic carbene intermediate, which has been successfully trapped by oxygen, allyltrimethylsilane, 2,3-dimethylbut-2-ene, pyrrole, acrylonitrile, 1,4-dimethoxybenzene, and also pyridine.
The generation and the reactivity of a triplet carbene intermediate has been supported by LFP, with the
detection of 2,6-naphthoquinone-O-oxide (530-650 nm) in the presence of O2. The electrophilic diradical character of the carbene has been supported by DFT calculations, using the B3LYP, PBE0, and MPWB1K functionals, with the 6-31+G(d,p) basis set and PCM solvation model
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