Microstructure elucidation of poly(epichlorohydrin) modified with thiol compounds using one- and two-dimensional NMR spectroscopy

Poly(epichlorohydrin) has been modified chemically using aromatic and aliphatic thiol compounds. The NMR results show that using both aromatic and aliphatic thiols, one achieves degrees of modification of up to 90% without any elimination side reaction. As a consequence no degradative chain-scission takes place. A microstructural analysis of the modified polymers has been carried out by ¹³C NMR, ¹H NMR and ¹³C DEPT spectroscopy. Additionally, 2D heteronuclear correlated spectroscopy (HMQC and HMBC) were used in order to determine the chemical shifts of quaternary carbons.     

Cu(I)-phosphine complex: An efficient catalyst for synthesis of 3-indole derivatives through one-pot MCR under mild conditions

An efficient copper (I) halotriphenylphosphine catalyzed one-pot multicomponent reaction (MCR) of 3-substituted indole derivatives has been developed using a variety of aldehydes (aromatic, aliphatic, and heteroaromatic), indole, and active methylene substrates such as malononitrile and ethyl 2-cyano acetate. This reaction proceeds smoothly and obtained good to excellent yields (68–93%) using water as green solvent under ambient conditions. The obtained products were confirmed by ¹H, ¹³C NMR, and mass spectroscopy techniques. The one-pot MCR occurs through formation of Knoevenagel adducts then followed by Michael addition of indole.     

Synthesis of 2-(4-amino substituted benzylidene) indanone analogues from aromatic nucleophilic substitution (SNAr) reaction

A novel, efficient and convenient procedure has been developed for the synthesis of 2-(4-amino-substituted benzylidene)indanone derivatives. In the first step, the reaction of 4-fluorobenzaldehyde with 5, 6-dimethoxy-2, 3-dihydro-1H-inden-1-one in the presence of NaOH in EtOH was described. In the next step, a variety of aliphatic and aromatic amines were reacted with 2-(4-fluorobenzylidene)-5, 6-dimethoxy-2, 3-dihydro-1H-Inden-1-one via aromatic substitution (S_NAr) reaction to produce 2-(4-aminobenzylidene)-5, 6-dimethoxy-2, 3-dihydro-1H-Inden-1-one derivatives as a novel class of 1-indanones. These products have been successfully prepared in good to excellent yields. ^1?H and ^13?C NMR, FT-IR spectroscopy and CHN analysis supported the proposed structures of the products.     

Reaktionen von fluoralkenen I. Zur nucleophilen reaktion von F-hept-1-en mit alkoholen

The reaction of F-hept-1-ene together with aromatic and aliphatic alcohols has been investigated. In the case of disodiumphenolsulfonate, $\text{trans}$-F-hept-2-enyl-1-oxybenzenesulfonate was formed, exclusively. The structure of this new fluorosurfactant was confirmed by means of ¹⁹FNMR. In contrast, phenoxide and alkoxide yield a mixture of products, including the isomers of allylic and vinylic substitution together with an addition product.     

Identification of microbial inhibitory functional groups in corn stover hydrolysate by carbon-13 nuclear magnetic resonance spectroscopy

Dilute-acid biomass hydrolysates contain biomass degradation products that are inhibitory to cell growth and fermentation. Overliming with Ca(OH)₂ has been found to be one of the most effective methods for detoxifying the dilute-acid hydrolysate for ethanol production. However, the mechanism of overliming is not well understood. Carbon-13 nuclear magnetic resonance (¹³C-NMR) spectroscopy was used to elucidate the functional groups involved in the overliming reaction. The ¹³C-NMR spectra showed that the major functional groups removed during the overliming process were aliphatic and aromatic acids or esters, and other aromatic and aliphatic compounds. Ketone and aldehyde functionalities were not detected in the spectra. This is the first time that ¹³C-NMR has been used to elucidate the overliming reaction.     

Functional polymers. XIX. Biuret oligomers and polymers of biologically active primary aliphatic amines

Biuret oligomers and polymers from primary aliphatic amines and aromatic or aliphatic diisocyanates have been synthesized. To demonstrate the feasibility of the synthesis of polybiurets, aliphatic primary amines with n-propyl, n-hexyl, n-octyl, and n-dodecyl groups have been incorporated. For the synthesis of biuret oligomers of biologically active primary aliphatic amines [8-(4-amino-1-methylbutylamino)-6-methoxyquinoline] (primaquine) and adamantanamine were selected. Primaquine was also incorporated into polyepichlorohydrin by nucleophilic substitution of the chlorine of the chloromethyl group by the primary aliphatic amino group of primaquine. The structure of the biuret polymers was established by elemental analysis, and by infrared ¹H- and ¹³C-NMR spectroscopic characterization. Several attempts to use primaquine as a diamine for the formation of condensation polymers, including reaction of primaquine with sebacoyl chloride (to form polyamides), or with diisocyanates (to form polyureas) were unsuccessful.     

The NMR Study of the Mechanism of Alkene Arylation with Anhydrides of Aromatic Acids

The main steps of the catalytic cycle of the alkene arylation reaction with the participation of anhydrides of aromatic acids as arylation agents were studied by ³¹P NMR spectroscopy. In contrast to the mechanism proposed earlier, palladium complexes containing benzoate anions as acidoligands were not found in the reaction mixture. It was found that the catalytic cycle of the reaction includes the steps of oxidative addition of Pd(0) formed in situ to the anhydride of acid, the substitution of acidoligand, and the elimination of the CO molecule. Further transformations probably take place according to the usual steps of the Heck reaction. It was shown that CO elimination is a limiting step.     

Reactivity of aryl chlorides with sodium sulfide in the synthesis of aromatic polyamidethioethers

The synthesis of aromatic copolyamidethioethers by reaction of dichlorobenzanilides with Na₂S has been studied. The reactivity of chlorine atoms is strongly dependent on the nature of the substituent in para position. It is related to the ¹³C NMR shifts of the relative carbons-the more deshielded, the more reactive-and hence to charge densities, agreing with aromatic nucleophilic substitution mechanisms. The results are discussed in relation to the various mechanisms which have been put forward for the reaction of Na₂S with 1, 4-dichlorobenzene (PPS synthesis).     

Copper(II)-acid co-catalyzed intermolecular substitution of electron-rich aromatics with diazoesters

The intermolecular aromatic substitution of N,N-dialkylanilines and alkoxybenzenes with diazoesters is shown to proceed in the presence of catalytic amounts of both copper(II) salt and acid (Lewis or Brønsted). This method is a mild and rare metal-free C-C bond formation reaction between aromatic (sp²) and aliphatic (sp³) carbons.     

Synthesis of Some Bromomethyl‐ and (4‐Bromomethyl)phenyl‐Derivatives of 1,4,8,11 Tetraaza[14] annulene and Their Corresponding Sulfanylmethylene‐Derivatives Using 3‐Substituted Trimethinium Salts

Four new 6,13‐di(bromomethyl)‐ and di[(4‐bromomethyl)phenyl]1,4,8,11‐tetraaza[14]annulene derivatives C , D , E , F were synthesized using the condensation reaction of the correspondingly substituted vinamidinium salts with aromatic amines in acetonitrile/acetic acid. The reaction of these annulenes with thiourea leads to the corresponding thiol derivatives G and H . The UV/vis spectral behavior of compounds C , D , E , F , G , H was examined in DMSO. Elemental analysis, IR, ¹H‐NMR, ¹³C‐NMR, and mass spectral data confirm the molecular structure of the newly synthesized compounds.     

Effect of isocyanate structure on deblocking and cure reaction of N-methylaniline-blocked diisocyanates and polyisocyanates

Two series of N-methylaniline-blocked isocyanates based on monomeric diisocyanates such as 4,4′-methylene bis(phenyl isocyanate), toluene-2,4-diisocyanate, isophorone diisocyanate and 1,6-diisocyanato hexane and their NCO terminated polyurethane prepolymer (polyisocyanates) were prepared and characterized thoroughly by FTIR, ¹H NMR, ¹³C NMR and EI-Mass spectroscopic methods. The blocking reaction of N-methylaniline with aromatic isocyanates and aromatic polyisocyanates occur faster when compared to the aliphatic isocyanates. The deblocking reactions of blocked isocyanates were carried out under dynamic and isothermal conditions using hot-stage FTIR spectrophotometer. The dynamic method was used to determine the deblocking temperature, and the isothermal method was used to calculate kinetics and thermodynamics parameters. Cure reactions of blocked isocyanates with hydroxyl-terminated polybutadiene were also followed to establish the structure-property relationship of the N-methylaniline-blocked isocyanates. The deblocking studies of blocked isocyanates reveal that the aromatic isocyanates undergo deblocking easily compared to aliphatic isocyanates. The rate of deblocking reaction of N-methylaniline-blocked aromatic polyisocyanates was found to be higher compared to N-methylaniline-blocked aromatic monomeric diisocyanate adducts. On the other hand, this trend was just reverse in the cure-reaction studies. The dissolution behavior of N-methylaniline-blocked isocyanates in Terathane-2000, polypropylene glycol-2000, polycaprolactone diol-2000 and hydroxyl-terminated polybutadiene-2500 was also studied and found that all adducts are soluble in these polyols.     

One‐pot,fast cyclopropanation reaction of indandione with various aldehydes in the presence of cyanogen bromide and trimethylamine

A new, fast, and easy one‐pot cyclopropanation reaction of aromatic and aliphatic aldehydes with 1H‐indene‐1,3(2H)‐dione and cyanogen bromide (BrCN) was developed for synthesizing 3′‐(aryl[alkyl])‐dispiro[indan‐2,1′‐cyclopropane‐2′,2′′‐indan]‐1,1′′,3,3′′‐tetrone in excellent yields in a short time (about 15 s) under basic media. All structures were characterized using IR, ¹H NMR, and ¹³C NMR spectroscopy techniques.     

Zinc templated synthesis—a route to get metal ion free tripodal ligands and lariat coronands, containing Schiff bases

A new series of tripodal receptors bearing imine linkages have been prepared in high yields, by a single step condensation reaction between tripodal aromatic amines and aldehydes, using zinc perchlorate as a template. The template cation leaves the pseudo cavity after the Schiff base condensation to give metal free multidentate ligands. These products have been characterized by ¹H, ¹³C NMR, IR, elemental analysis, UV-vis absorption spectroscopy and X-ray crystallographic studies. It has been seen that the presence of a coordinating atom such as O, S, and N at position-2 with respect to the carbonyl group, is mandatory for the reaction to proceed. The template reaction has been also successfully employed to synthesize a lariat type coronand by reacting the tripodal amine with a dialdehyde.     

High resolution solid‐state 13C‐NMR study of as‐cured and irradiated epoxy resins

This article presents the effects of strong ionizing radiations on the physico‐chemical modifications of aliphatic or aromatic amine‐cured epoxy resins based on diglycidyl ether of bisphenol A (DGEBA). Such epoxy resins have a considerable number of applications in the nuclear industrial field and are known to be very stable under moderate irradiation conditions. Using extensively high resolution solid‐state ¹³C‐NMR spectroscopy we show that the aliphatic amine‐cured resin (DGEBA‐TETA) appears much more sensitive to gamma rays than the aromatic amine‐cured one (DGEBA‐DDM). On the one hand, qualitative analyses of the high resolution solid‐state ¹³C‐NMR spectra of both epoxy resins, irradiated under similar conditions (8.5 MGy), reveal almost no change in the aromatic amine‐cured resin whereas new resonances are observed for the aliphatic amine‐cured resin. These new peaks were interpreted as the formation of new functional groups such as amides, acids and/or esters and to alkene groups probably formed in the aliphatic amine skeleton. On the other hand, molecular dynamics of these polymers are investigated by measuring the relaxation times, T_CH, T_1ρH and T_1C , before and after irradiation. The study of relaxation data shows the formation, under irradiation, of a more rigid network, especially for the aliphatic amine‐cured system and confirms that aromatic amine‐cured resin [DGEBA‐4,4′‐diaminodiphenylmethane(DDM)] is much less affected by ionizing radiations than the aliphatic amine‐cured resin [DGEBA‐triethylenetetramine(TETA)]. Moreover, it has been shown that the molecular modifications generated by irradiation on the powder of the aliphatic‐amine‐cured resin appear to be homogeneously distributed inside the polymers as no phase separations can be deduced from the above analyses. Copyright © 2001 John Wiley & Sons, Ltd.     

13C NMR of polycyclic aromatic compounds. A review

The analysis of the ¹³C NMR spectra of polycyclic aromatics is discussed briefly. Basic trends of chemical shifts are mentioned, but the emphasis is placed on substituent-induced chemical shifts (SCS). Semi-empirical approaches and regressional analysis are treated. The factors controlling SCS are discussed and steric, mesomeric and π-inductive effects are analysed. CH, CF, CC, CP and C, Metal coupling constants are investigated and the influence of steric effects, bond order, mesomerism and angle distortions in relation to some of these coupling constants is discussed. Relaxation times are described in a series of compounds. The effects of dissolved oxygen or radicals are shown and the use of T₁ as a monitor of molecular tumbling is depicted. The impact of ¹³C NMR on the understanding of charged aromatic species, both positive and negative ions, is mentioned and new information about reaction intermediates in electrophilic aromatic substitution is outlined. The possibility of using ¹³C NMR to investigate charge transfer complexes is also discussed. Among other subjects treated are automerization, deuterium exchange and biosynthetic incorporation of labelled materials and, finally, quantitative analysis is briefly touched upon.     

Survey Reactivity of Some Substituted Quinazolinones with Pentafluoro(chloro)pyridine

A new series of 4‐hetroaryl substituted quinazolines were designed and synthesized by the reaction of pentafluoro(chloro)pyridine and 2‐substituted quinazolinone. The aromatic nucleophilic substitution of pentafluoro(chloro)pyridine with quinazolinone occurs at the 4‐position of pyridine ring by the oxygen site (O‐centered nucleophile) of quinazolinone. The structures of all the compounds were confirmed by IR, ¹H NMR, ¹⁹F NMR, and ¹³C NMR spectroscopy as well as elemental analysis.     

Fluoroalkene chemistry: Part 1. Highly-toxic fluorobutenes and their mode of toxicity: reactions of perfluoroisobutene and polyfluorinated cyclobutenes with thiols

The reactions of four highly-toxic fluorobutenes - perfluoroisobutene (PFIB), 1-hydropentafluorocyclobutene (1-H), hexafluorocyclobutene (HFCB) and 3-chloropentafluorocyclobutene (3-Cl)—with propanethiol, 2,6-dimethoxybenzenethiol and N-acetylcysteine isopropyl ester were studied. PFIB and HFCB reacted with two molar equivalents of the aliphatic thiols, but with only one molar equivalent of the aromatic thiol (presumably due to steric hindrance) and resembled phosgene in their reactivity. The fluorocyclobutenes 1-H and 3-Cl reacted with one and up to three molar equivalents of the aliphatic thiols, respectively, but with only one molar equivalent of the aromatic thiol. The products of allyl and vinyl substitution were isolated and characterised as fully as possible. The inhalation toxicities of the fluorocyclobutenes to rodents correlated with the number of easily-displaceable fluorine substituents, supporting the contention that toxicity is due to reaction with biological thiols in the lung.     

A Convenient Synthetic Method and Spectral Characterization of New Tetrahydro[1,3]oxazinothieno[2,3‐c]isoquinoline and Its Pyrimidine Derivatives

Acetylation of 1‐amino‐5‐morpholin‐4‐yl‐6,7,8,9‐tetrahydrothieno[2,3‐c ]isoquinoline‐2‐phenyl carboxamide 3 afforded the corresponding tetrahydro[1,3]oxazinothieno[2,3‐c ]isoquinolinone compound 4 . The oxazinone compound 4 underwent nucleophilic substitution reactions with various primary aliphatic and aromatic amines including some sulfa drugs such as sulfanilamide, sulfaguanidine, and sulfathiazole to afford the substituted pyrimidinone compounds 6–10 . Chlorination of the pyrimidinone 10 with phosphorus oxychloride yielded the chloropyrimidine derivative 11 . The latter compound was used as a versatile precursor for the synthesis of other heterocyclic rings containing the tetrahydropyrimidothienoisoquinoline moiety 12–23 through reaction with a variety of organic reagents. The newly synthesized compounds were fully characterized by elemental and spectral analyses, including melting point, TLC, and FT IR and ¹H NMR spectroscopy, as well as ¹³C NMR and mass spectroscopy for most of them. These molecules should allow to us in the future to investigate their pharmacological activities.     

Calculation of 13C NMR chemical shifts for aromatic carbons in polyalkylated benzenes

¹³C NMR spectra of a large number of polyalkylated benzenes with branched and linear aliphatic chains have been studied. This resulted in the development of a general procedure that can be used for the calculation of the aromatic chemical shifts in any polyalkylated benzene.     

O-Alkylation of a lignite humic acid by phase-transfer catalysis

A mild phase-transfer catalytic reaction has been conducted to O-alkylate the acidic functions of a lignite humic acid (HA), using tetrabutylammonium hydroxide as the phase-transfer catalyst. The HA acidic functional groups were made to react, in tetrahydrofuran, by nucleophilic substitution with several alkyl halides—methyl iodide, and ethyl, propyl, and butyl, and benzyl bromide. The occurrence of the O-alkylation reaction was assessed by elemental analysis and ¹H NMR, CPMAS ¹³C NMR, and FTIR spectroscopy. Bonding of alkyl groups increased the carbon and hydrogen content and the H/C ratios of all the humic reaction products. Increased nitrogen in the reaction products suggested incomplete removal of the phase-transfer catalyst after purification of the alkylated HA. ¹H NMR and CPMAS ¹³C NMR spectra of alkylated products provided evidence of the successful occurrence of the alkylation reactions. Infrared spectra confirmed the NMR results, revealing the characteristic absorption of newly formed alkyl and aryl ethers and esters in the alkylated products and C–H stretching in the aromatic ring of the benzylated derivative. These findings indicate that humic matter can be successfully alkylated with several different alkylating groups by catalysed phase-transfer reaction. This O-alkylation reaction has the advantage of being mild, versatile, and high-yielding compared with traditional methylation reactions applied to HA. The possibility of introducing different alkyl groups into the HA by a mild phase-transfer reaction may become useful by enabling improved fractionation of humic supramolecular associations and further understanding of the molecular nature of humic substances.