Reductive alkylation of illinois No. 6 coal. 1H and 13C n.m.r. spectra of the 13C-enriched alkylation products

The reductive alkylation of Illinois No. 6 coal has been carried out using potassium and naphthalene in tetrahydrofuran and methyl-¹³C and butyl-1 -¹³C iodides to alkylate the resultant polyanion. The soluble products of the reductive alkylation reaction were isolated by extraction and chromatography. Proton and carbon n.m.r. spectra were recorded. The intense resonance signal at δ3.95 which appears in the proton n.m.r. spectra of Illinois No. 6 coal butylated with unenriched butyl iodide is split into a doublet by the ¹³C nuclei. Similar results were obtained for the methylation products. The chemical shift and coupling interaction establish that aryl ethers are a very important constituent of the alkylated coal. The carbon n.m.r. spectra of the coal alkylated with ¹³C-enriched alkyl iodides are intense. The resonances of the C-alkylation products appear in a single broad band with a maximum intensity in spectral regions compatible with the formation of the reductive alkylation products of certain polynuclear aromatic hydrocarbons or the base-catalysed alkylation of certain benzylic carbon atoms. The resonances of the N -alkylation products appear in two distinct bands. These resonances are tentatively assigned to amines produced as a result of reductive alkylation of heterocyclic compounds. The resonances of the 0-alkylation products appear in three distinct bands which can be assigned to alkyl aryl ethers, alkyl aryl ethers with substituents at the adjacent positions, and to alkyl carboxylates. The ratio of ethers to carboxylates in the soluble alkylation products was determined to be 7.8 for butylation and 8.0 for methylation. The Chromatographic fractions contain different amounts of C-, N-, and 0-alkylation products. This finding suggests that the coal structure is not highly uniform.     

Solid state magnetic resonance spectra of Illinois No. 6 coal and some reductive alkylation products

Illinois No. 6 coal and its reductive methylation and butylation products have been studied by magnetic resonance techniques. Conventional CP-MAS¹³Cn.m.r. spectroscopy indicates that 62% of the carbon atoms in the coal are aromatic and that about 6% of the carbon atoms are carbonyl. Esters are more abundant than carboxylic acids. The resonances of methoxy groups and other novel etheric carbon atoms are apparent in the high field region. Dipolar dephasing experiments suggest that methyl carbon atoms constitute no more than 16% of the carbon, methylene and methine carbon atoms about 14% and quaternary aliphatic carbon atoms about 2%. The dipolar dephasing experiments in conjunction with previous work also permit estimates of the hydrogen atom distribution. The THF-insoluble products obtained in the reductive alkylation reactions with¹³C-enriched alkylating agents contain paramagnetic and ferromagnetic substances that adversely influence the solid state n.m.r. spectra. However, good ¹³C n.m.r. spectra were obtained after these substances were extracted with aqueous hydrochloric acid. The O:C alkylation ratios are 1.2 and 1.0 for methylation and butylation, respectively. Dipolar dephasing experiments establish that the decay constants of functional groups in the whole coal and of C- and O-methyl-¹³C and C- and O-butyl-1 -¹³C nuclei in the labelled coal molecules are very similar to those of reference compounds. These findings suggest that the decay constants measured for the ¹³C nuclei in coals and coal-derived solids provide reliable information about their degree of substitution.     

Investigation of the chemical structures of coking and non-coking coals in original and reductively alkylated solid states via 13C n.m.r. and i.r. spectroscopies

Chemical structures of four Turkish coals in original and reductively alkylated forms were investigated in the solid state by CP/MAS ¹³C n.m.r. and i.r. spectroscopies. Dilatation properties of these samples were also determined. It was observed that, while the aliphatic parts of the coking coals are mainly composed of short and straight alkyl groups and alicyclic structures, the aliphatic parts of the non-coking coals are to a larger extent composed of branched chains and/or alicyclic structures. It was concluded that ether bonds linking aromatic units are more prominent in the coking coals, whereas in the non-coking coals aromatic-O-aliphatic and/or alicyclic ethers dominate. The degree of condensation of aromatic structures was found to be higher in the coking coals, and the extent of reductive alkylations was higher in comparison with the non-coking coals. Non-coking coals were found to be alkylated preferentially at their phenolic oxygens. Difference spectra were found to be very useful in following organic chemical structural changes that accompany reductive alkylation.     

Structure analysis of coals by resolution enhanced solid state 13C n.m.r. spectroscopy

The application of experimental n.m.r. and chemical resolution enhancement techniques in cross-polarization/magic angle spinning (CP/MAS) ¹³C-n.m.r. spectroscopy yields spectra of coals and coalderived solids which contain structural information within the hybridization resonance envelopes. The sp²- and sp³-carbon resonance manifolds are partitioned into components arising from carbon centres bonded directly to oxygen, hydrogen and only other carbon atoms. The unique, observable chemical shift bands in the spectrum are increased from three (the relative areas of the sp²- and sp³-carbon resonance envelopes and a separate carbonyl band) to nine. This resolution permits the principal structural changes in chemically-modified coals to be mapped in unprecedented detail. The reductive alkylation of a typical bituminous coal has been examined by this method.     

Study of the changes in i.r. spectra bands of coal after reductive alkylation

Depolymerization reactions of a Spanish bituminous coal, such as reductive hydrolysis and alkylation, and O-alkylation, were investigated by Fourier transform infrared spectroscopy (FT-i.r.). The spectra show that the reductive hydrolysis increases the phenolic hydroxyl groups, whereas these decrease by alkylation. These changes in the OH group content were studied in relation to variations in the absorbances at 3800–2000, 1700, 1600 and 1112 cm⁻¹, and some linear correlations were found, which seem to indicate a clear contribution of the OH groups to the intensity of the broad band near 1600 cm⁻¹. The influence of the phenolic OH groups on the C=O vibration frequency at 1700 cm⁻¹ was also studied.     

Reductive alkylation of Illinois No. 6 coal in liquid ammonia

The reductive alkylation of Illinois No. 6 coal was investigated using alkali metals and alkyl halides in liquid ammonia. Potassium is the most effective reducing agent and butyl iodide is the most effective alkylating agent for the preparation of coal alkylate that is soluble in tetrahydrofuran. The overall yield of soluble product is often improved through the reaction of the tetrahydrofuran-insoluble portion of the initial reaction products with an alkylating agent in the presence of tetrabutylammonium hydroxide. The infrared spectra of these materials suggest that the phase transfer agent catalyses the esterification of residual carboxylic acid functions. The intermolecular interactions between such acid groups and acceptor groups markedly restrict the solubility of the coal alkylate. The gel permeation chromatograms of the soluble reaction products are essentially featureless with only modest maxima at short and long elution volumes. The proton and carbon nuclear magnetic resonance spectra of the reductive methylation products, prepared using methyl-¹³C iodide, suggest that carbon alkylation exceeds oxygen alkylation and that the alkylation of phenolic groups is the dominant O-alkylation reaction. The spectra also suggest that fewer ethers are cleaved in the reaction in liquid ammonia than under the conditions of the Sternberg reaction.     

Kinetics of reductive alkylations of phenylenediamines: Influence of substrates isomeric structure

Reductive alkylation of ortho-, meta- and para-phenylenediamines (PDAs) with methyl ethyl ketone (MEK) has been studied in a semi-batch slurry reactor in the presence of a commercial 3% Pt/Al₂O₃ catalyst. It was observed that the PDA isomers differ remarkably from each other in their activity in reductive alkylation and product distribution. The activity was found to decrease in the following order: PPDA>OPDA>MPDA. To understand the substrate structure–activity correlation, the homogeneous equilibrium reactions involved in the alkylation step and the overall catalytic reactions were studied separately. Kinetics of reductive alkylation of PDAs with MEK as a solvent and alkylating agent with 3% Pt/Al₂O₃ catalyst was studied in a semi-batch slurry reactor over a temperature range of 373–453 K and pressure range of 2.07–6.21 MPa. Semi-batch slurry reactor models were developed and kinetic parameters were estimated by fitting the integral batch reactor data at different temperatures to understand the influence of different reaction steps on the activity and selectivity of different products.     

Preparation of 2-Aroyl-3-methyl-1H-1,4-benzothiazines. ESR Study of 2-benzoyl-1,3-dimethyl-1H-1,4-benzothiazine

2-Aroyl-3-methyl-1 H-1,4-benzothiazine ylids ( 2a – k ) were prepared by alkylation of the corresponding 4H-benzothiazines 1 . The ylids 2 are labile at room temperature; proper analytical and ¹H-n.m.r. data were obtained for their picrates. E.s.r. studies of u. v. irradiated polycrystalline form of ( 2 ; R¹ = Me, R² = H) gave evidence for a long-lived benzothiazinyl radical with the odd electron residing on nitrogen 6 .     

Reductive ethylation in ethereal solvents

Organic compounds, in particular anthracene and naphthalene, and two coals have been reductively ethylated in tetrahydrofuran (THF) and diglyme using alkali metals to form anions and ethyl iodide to produce ethylates. Product distributions were sensitive to experimental conditions. The rate of anion formation was controlled by their rate of desorption, probably as contact ion pairs, from the alkali metal surface. The enthalpy of formation of a solvated contact ion pair was ≈500 kJ mole^?1 mainly due to dipole-solvent interaction. 18-crown-6 ether was used to diagnose that, when treated with potassium in THF, anthracepe gave solvated contact ion pairs and probably di-anions whose reactions were characterized by the formation of ethyldihydroanthracene. Naphthalene under identical conditions gave loosely solvated mono-anions which reacted by electron transfer to give diethyldihydronaphthalene. With other alkali metals anthracene and naphthalene gave similar product distributions. The behaviour of other polynuclear aromatic hydrocarbons and of two coals was classified in the same way. It is suggested that when coals are readily solubilized by reductive alkylation mono-alkyldihydro products will predominate.     

Reductive and non-reductive methylation of high-sulphur coals studied by atmospheric pressure-temperature programmed reduction technique

Two kinds of high sulphur content coals Mequinenza and Illinois No. 6 have been subjected to reductive and non-reductive alkylation. The reductive alkylation was performed in the potassium/liquid ammonia system, while the non-reductive one was performed according to the procedure proposed by Liotta. In both processes the alkylating reagent was iodomethane. The products were subjected to elemental analysis and studied by IR spectroscopy and Atmospheric Pressure-Temperature Programmed Reduction (AP-TPR) technique. It has been established that much more information can be elicited from AP-TPR results obtained for the samples after modification by reductive or non-reductive alkylation than for non-modified coals. The Mequinenza coal has been found to contain aryl thiols and almost no alkyl thiols, whereas the Illinois No. 6 coal has been shown to contain alkyl thiols while practically no presence of aryl thiols has been detected.     

Synthese und Strukturermittlung von Sulfamoyl-guanidinen

Synthesis and Structure Elucidation of Sulfamoyl Guanidines A series of sulfamoyl guanidines 2a--hyphen;p and 4 was synthesized by addition of sulfurylchloride to dialkylcyanoamides and subsequent aminolysis of the N,N-dialkyl-N′-chlorosulfonyl-chloroformamidines with primary or secondary amines. Advantageously, the aminolysis can be performed with trimethylsilylamines as amine component by continuous withdrawing of the formed trimethylchlorosilane. Phase transfer catalyzed methylation led to a specific alkylation of the sulfamoyl group to form the 2-(aryl-methyl-sulfamoyl)-guanidines ( 5a--hyphen;5g, 5h ). All compounds were characterized by m.s.-, i.r.-, ¹H-n.m.r.- and ¹³C-n.m.r.-spectra. I.r. and ¹H-n.m.r. data show the existence of an intramolecular hydrogen bonding between the guanidine NH group and the SO₂ group.     

Reductive alkylation of coals in liquid ammonia

The reductive alkylation of two different rank coals was investigated using metallic potassium and alkyl iodide in liquid ammonia. The reduction reaction alone increases the dissolution of the coals in dichloromethane only to a very small extent. However, the reduction process in conjunction with alkylation leads to readily dichloromethane soluble products. The solubilization of alkylated coals depends on the type of coal and the length of the substituent alkyl chain. The extracts were characterized by infra red spectroscopy, molecular mass, hydrocarbon class analysis and elemental analysis.     

高分散型纳米级Pd/Fe对4-氯苯酚的还原脱氯

引言氯酚类化合物在医药、农药、塑料、抗氧剂、涂料、制革和造纸等生产过程中有着广泛的应用,是首批列入斯德哥尔摩国际公约的12类持久性有机污染物(POPs)之一,属于典型的环境雌激素[1]。因此,如何修复氯酚类化合物对环境的污染已成为当今环境科学界迫切需要解决的问题。在众多氯酚类化合物的治理方法中,利用廉价的金属铁(Fe0,zero-valent iron,ZVI)及其化合物脱氯为含氯有机物的处理提供了一种具有前景的途径,该法具有简单实用和操作费用低等特点[2-5]。     

Average structure of extracts of a butylated coking coal

A high-vitrinite coking coal (87%C, daf) was subjected to reductive and non-reductive butylation and the yields of their chloroform extracts (butylated coal basis) were 67.2 and 17.1 wt% respectively. The extracts were separated by adsorption and gel permeation chromatography into a few fractions so that the latter were in ‘equimolar’ ratios (considering the average molecular masses). The soluble fractions were characterized by elemental and average molecular mass analysis and data derived from ¹H and ¹³C n.m.r. spectra and average structural models of the fractions were constructed.     

4′-tert-Alkylbenzo[15]krone-5-ether. Synthesen und Kaliumthiocyanat-Komplexe

4′-tert-Alkylbenzo[15]Crown-5-Ether. Syntheses and Complexes with Potassium Thiocyanate The title compounds 4 are synthesized either by alkylation of pyrocatechole 1 in 4-position and followed by ring closure with 1,11-dichloro-3,6,9-trioxaundecane or by alkylation of benzo[15]-crown-5 3 . In most cases the way first mentioned gives better results. Analytical samples of the alkylated benzo[15]crown-5 ethers 4 are obtained through complexing with KSCN. Physical data and ¹H-n.m.r.-spectra of 5 new pyrocatecholes 2 and 6 new benzo[15]crown-5 ethers 4 are given.     

Late-Stage Hydrocarbon Conjugation and Cyclisation in Synthetic Peptides and Proteins

The conventional S-alkylation of cysteine relies upon using activated electrophiles. Here we demonstrate high-yielding and selective S-alkylation and S-lipidation of cysteines in unprotected synthetic peptides and proteins by using weak electrophiles and a Zn²⁺ promoter. Linear or branched iodoalkanes can S-alkylate cysteine in an unprotected 38-residue Myc peptide fragment and in a 91-residue miniprotein Omomyc, thus highlighting selective late-stage synthetic modifications. Metal-assisted cysteine alkylation is also effective for incorporating dehydroalanine into unprotected peptides and for peptide cyclisation via aliphatic thioether crosslinks, including customising macrocycles to stabilise helical peptides for enhanced uptake and delivery to proteins inside cells. Chemoselective and efficient late-stage Zn²⁺-promoted cysteine alkylation in unprotected peptides and proteins promises many useful applications.     

Reduction alkylation of aromatic hydrocarbons

The reductive alkylation of the aromatic hydrocarbons naphthalene and perylene is investigated. Reduction with potassium metal in tetrahydrofuran at room temperature leads to the naphthalene radical anion and the perylene dianion, which react with alkyl iodides to yield di-alkyl di-hydro species. The reductive alkylation of coals can be more complex.     

氨基酸的N-甲基化方法

光学纯的／N-甲基-α-氨基酸是许多具有生物活性的天然产物化合物的重要组成部分。本文综述了近年来α-氨基酸的N-甲基化方法,主要包括直接甲基化方法,还原胺化法,通过生成噁唑烷酮中间体的甲基化方法,以及其他特殊方法,如α-叠氮酸类化合物的还原烷基化、应用Mitsunobu反应、应用亚胺氮正离子的逆Diels-Alder反应等方法。     

Alkylation of phthalic anhydride in a low-temperature methane plasma

The results of the reductive alkylation of phthalic anhydride with a low-temperature methane plasma are reported. The reaction products were identified by mass-selective chromatography (GC/MSD).     

Reactivity of O-methylated Illinois No. 6 coal towards alkyllithiums/methyl iodide

An O-methylated Illinois No. 6 vitrain was treated repeatedly with a series of C-H indicator bases of known pK_a and quenched with ^13,14C-methyl iodide. The extent of ¹⁴CH₃ incorporation depended strongly upon base strength, increasing in the order 9-phenylfluorenyllithium < fluorenyllithium < trityllithium. A significant number of methyl groups ($\text{0.7–1.2}\text{100}$ coal carbons) were introduced with fluorenyllithium and trityllithium as the base. Additional methyl groups were added upon a second and third treatment with base and alkylating agent. After three treatments, the number of added methyl groups had doubled. The extent of base reagent incorporation was established by parallel experiments using ¹⁴C-enriched bases. CP/MAS ¹³C n.m.r. of the first coal alkylation product using trityllithium and ¹³C-enriched methyl iodide was consistent with predominantly C-alkylation. From these results, a unified picture for coal structure emerges which contains a distribution of reactive C-H sites, distinguishable on the basis of their acid-base properties. Possible reactive sub-structures are considered.