Presence Of Nucleophilic Reagents Research Articles

N‐Acyloxyphthalimide as Multitasking Directing Group for Sequential C‐H Functionalization

AbstractN‐Acyloxyphthalimide has been demonstrated as a multitasking directing group considering its easy accessibility, multiple reactive sites, and multifarious transformations available to generate valuable structural diversified scaffolds. Polysubstituted heterocycles, such as isocoumarin, isoquinolone, and its second annulation products, could be obtained from N‐acyloxyphthalimide and alkynes through a one‐pot reaction in the presence of nucleophilic reagents. Additionally, the ester group possessed on the resulting heterocycles could serve as a new building block to direct further functionalization.

Synthesis, stability in solutions, and spectral and thermal properties of alkyl-substituted 3,3′-bis(dipyrromethene) hydrobromides

3,3′-Bis(dipyrromethene) dihydrobromides (H2L · 2HBr) with various types of alkylation have been synthesized. On the basis of IR, 1H NMR, and electronic absorption spectra, spectrophotometric titration, and thermogravimetry, conclusions have been drawn about the influence of structural factors on the optical and thermal properties and salt stability in solutions. An increase in the degree of alkylation causes a significant high-frequency shift of the N-H stretching vibration band in the IR spectra, an upfield shift of the 1H NMR signals of NH protons, a decrease in the auxochromic effects of protons on the aromatic system of the chromophore, and an increase in the salt stability in solutions in the presence of nucleophilic reagents and in the thermal stability in air and argon.

Reactivity of syringyl quinone methide intermediates in dehydrogenative polymerization I: high-yield production of synthetic lignins (DHPs) in horseradish peroxidase-catalyzed polymerization of sinapyl alcohol in the presence of nucleophilic reagents

It is known that the conventional dehydrogenative polymerization of sinapyl alcohol (S-alc) gave syringyl synthetic lignins (S-DHPs), but in extremely low yields. In this article, to examine the contribution of syringyl quinone methide intermediates (S-QM) on S-DHP production, horseradish peroxidase (HRP)-catalyzed dehydrogenative polymerization of S-alc was carried out in the presence of nucleophilic reagents that promote the rearomatization of S-QM. First, the HRP-catalyzed polymerization of sinapyl alcohol γ-O-β-D-glucopyranoside (isosyringin, iso-S), which allows us to monitor the polymerization process in a homogeneous aqueous phase, was utilized for screening of a nucleophile used as an S-QM scavenger. Monitoring of iso-S polymerization in the presence of various nucleophilic reagents by UV spectroscopy and gel permeation chromatography with photodiode array detection (GPC-PDA) revealed a high ability of azide ion to convert oligomeric S-QM efficiently to S-DHP. Accordingly, azide ion was utilized as an S-QM scavenger in HRP-catalyzed polymerization of S-alc, which resulted in high-yield production of S-DHPs (∼83%), as expected. The 1H-, 13C-, and 2D-HSQC NMR investigations on the resulting S-DHPs clearly demonstrated that azide ion efficiently performed nucleophilic additions to the C-α of S-QM during the polymerization. These results provide experimental proof that the low reactivity of S-QM with nucleophiles (such as water, phenolic, and aliphatic hydroxyl groups) in the conventional polymerization system critically impedes the production of S-DHPs from S-alc.

Insight into the Reactions of Trifluorovinylsilanes with Aromatic Aldehydes

AbstractThe conditions for the selective addition of trialkyl(trifluorovinyl)silanes to the C=O bond of aromatic aldehydes in the presence of cesium fluoride to give the corresponding“silylated” alcohols in high yields was performed. The reactivity of the “silylated” alcohols in the presence of nucleophilic reagents and Brönsted acids was studied. On the basis of isolated compounds and of intermediates detected by NMR spectroscopic methods, several reaction pathways are proposed. Significant differences between the reaction behaviour of triethyl(trifluorovinyl)silane and trimethyl(trifluoromethyl)silane under comparable conditions are pointed out; the differences can be attributed to the highly reactive trifluorovinyl group. The reactions of the “silylated” alcohols proceed with high stereoselectivity to give propenes, acid fluorides and acids of the (E) isomers in better than 98 % purity. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Synthesis, kinetics and mechanism of nucleophilic substitution in octahedral (cat)2Sn(py)2

Dicatecholatodipyridinetin(IV) in nitrobenzene showed an increase in molar conductance with time, suggesting solvation of the complex. In the presence of nucleophilic reagents, such as SOCl2, C6H5COCl and CH3COCl, the conductance increased sharply owing to the substitution of pyridine by chloride ions. The data for the rate constant of solvation (k s) and for nucleophilic substitution (k 1 and k 2) have been calculated and it was found that the solvation is a slower process compared to the substitution by chloride ions, i.e., k1, k 2 > k s. The nucleophilic substitution reaction follows the SN1 mechanism.

Electronic Absorption Spectra of Alkyl-Substituted Dipyrromethenes and Biladienes-a,c in Organic Solvents

3,3',5,5'-Tetramethyl-4,4'-dibutyldipyrromethene-2,2' and 1,3,7,13,17,19-hexamethyl-2,8,12,15-tetrabutylbiladiene-a,c hydrobromides undergo deprotonation in electron-donor solvents or in the presence of nucleophilic reagents. The rate and depth of the process depend on the electron-donor properties of the solvent, concentration, and degree of self-association of the chromophore molecules. Under analogous conditions, partial decomposition of the biladiene-a,c chromophore occurs.

Synthesis of Novel Heteroaromatic Polyfused as‐Triazines by Ring Transformation[1]

AbstractRing transformation of the tricyclic furo‐fused as‐triazinium salt 1 in the presence of nucleophilic reagents (e.g. sodium hydrogensulfide, sodium salts of malonic ester, ethyl cyanoacetate, acetylacetone, dimedone, or malononitrile) leads to the two new heteroaromatic ring systems thieno[2,3‐e]pyrido[1,2‐b]‐as‐triazinium salt (5) and differently substituted cyclopenta[e]pyrido[1,2‐b]‐as‐triazine compounds (8, 9, 10, 11, and 13).

1H and 13C NMR studies of substituted isoquinolinium derivatives in different solvents

Abstract1H and 13C NMR data for 1‐cyano‐, 4‐cyano‐, 4‐bromo‐ and 4‐bromo‐5‐nitro‐substituted isoquinolines, isoquinoline N‐oxides and N‐methoxy and N‐ethyl salts in different solvents are reported. The substituent chemical shifts are discussed with regard to the reactivity of the N‐methoxy compounds in the presence of nucleophilic reagents.

ChemInform Abstract: α‐Hydroxyalkylphosphonic Acid Dichlorides. Synthesis, Spectroscopic Properties, and X‐Ray Analysis.

AbstractPhosphorus trichloride (I) reacts with the carbonyl compounds (II) in the presence of nucleophilic reagents (H2O, AcOH, H3PO3) to give the title compounds (III).

Electrochemistry of phosphaferrocenes: III. Reaction of nucleophiles with the phosphaferrocenium cations

A comparative electrochemical study of the oxidation of ferrocene and three phosphaferrocene complexes: 1,1′-diphosphaferrocene, 3,3′-dimethyl-1-phosphaferrocene and 3,3′,4,4′-tetramethyl-1,1′-diphosphaferrocene in the presence of nucleophilic reagents (X = Cl, Br; L = o-phen, bipy) has shown that phosphaferrocenium cations are less stable than ferrocenium cation towards nucleophilic attack. It has been shown that the electron-withdrawing groups on the (η 5-C 5H 5) ligands are responsible for ligand exchanges on the oxidized species. The main products of the ligand exchange have been identified, and a general reaction scheme is proposed.

Reaction of 1,1-dichloro-1-nitrosoalkanes with trivalent phosphorus acid chlorides

1,1-Dichloro-1-nitrosoalkanes react with trivalent phosphorus acid chlorides not containing a P-O ether bond in the presence of nucleophilic reagents (sulfur dioxide, ethanethiol) to produce phosphorylated alkylchloroformoximes. This is rationalized in terms of intermediate O-alkylchloroformiminoyldichlorophosphorane formation.

ChemInform Abstract: Reaction of Diethylchlorophosphine with Cyclohexane in the Presence of Nucleophilic Reagents.

AbstractTreatment of diethylchlorophosphine (I) with cyclohexanone (II) in the presence of butanol (III) gives the phosphine oxides (IV) and (V).

ESR and 1H NMR studies of a new class of nitroxyl, nitronylnitroxyl and iminonitroxyl radicals

AbstractA new synthesis of nitronylnitroxyl (NNR), iminonitroxyl (INR) and nitroxyl radicals (NR) is suggested, involving oxidation of 4H‐imidazol di‐N‐oxides with O2 or PbO2 in the presence of nucleophilic reagents. This method allowed the preparation of radicals which could not be synthesized by known procedures. These radicals were studied by ESR and 1H NMR spectroscopy. The hyperfine interaction constants of the NNR were measured and assigned (in some cases radicals containing 15N were used). The influence of protonation and deprotonation of functional groups (OH, NH2) in the NNR on their ESR spectra was investigated and the pK values of these radicals were measured by ESR.Differences between the ESR spectra of two isomeric INR were found, and the structures of these radicals were established by 1H NMR. Changes in spin density delocalization in 3‐imidazoline 3‐oxide nitroxyl radicals were studied, and the spin density was found to be ‘pushed out’ to the peripheral fragments of these radicals on increasing the number of methoxy groups in the α‐position to the N—O. fragment. Hindered rotation around the σ‐bond of a bulky substituent in the α‐position to the N—O. fragment was detected by ESR. The activation energy of this hindered rotation was ΔE = 30±1.7 kJ mol−1.

Luminescence studies on physostigmine, rubreserine and adrenochrome

Fluorescence and phosphorescence spectra of physostigmine (eserine) are determined and compared with those reported for the phenyl carbamate pesticides Matacil and Zectran. The conversion of physostigmine to rubreserine is studied in the presence of nucleophilic reagents and inhibitors. Spectral characteristics of rubreserine and adrenochrome are compared with particular reference to the adrenolutin reaction. The fluorometric estimation of physostigmine is described.

The reaction of metallic mercury with alkyl halides in the presence of nucleophilic reagents

1. In the reaction of normal butyl iodide with metallic mercury in the presence of sodium iodide in air, butylmercury iodide and butyl ethyl ether are formed. The influence of a number of factors upon this reaction was studied. 2. Metallic mercury is activated by mercurous iodide and enters into a reaction at room temperature with normal butyl iodide, giving an organomercury compound.