1H NMR study of the inclusion of Costa-type organocobalt(III) complexes in cyclodextrins

The inclusion behavior between Costa-type complexes and cyclodextrins (CDs) was studied by 1H NMR in aqueous solution. The results indicated that 1:1 inclusion complex was formed, in which the alkyl group of the guest was included in the cavity of CDs. The stability constants of the inclusion complexes were determined by the quantitative 1H NMR method. The effects on stability constants were discussed when various host and guest compounds were used.     

Surface modification of hydroxyapatite to avoid bacterial adhesion

Hydroxyapatite was surface-modified by adsorption of nonionic polymers carrying phosphate groups as anchoring groups. A combination of alcohol ethoxylate and alkyl phosphate was also used. The possibility of interfering with early microbial colonization on apatite, mimicking the tooth surface, was investigated using radiolabelledStreptococcus mutans as model bacteria. The polymers, a nonionic cellulose ether and an EO/PO block copolymer based on polyglycerol as starting alcohol, were effective in buffer but gave only limited reduction of bacterial adhesion when the apatite had been pretreated with saliva. A 11 molar mixture of alcohol ethoxylate and alkyl phosphate was effective both with and without saliva, however. Studies with¹⁴C-labeled compounds, as well as microelectrophoresis experiments, indicate that an unsymmetrical double layer is formed on the apatite surface with predominantly alkyl phosphate in the inner layer and with alcohol ethoxylate pointing towards the water phase.     

Triethylaluminum- or triethylborane-induced free radical reaction of alkyl iodides and alpha,beta-unsaturated compounds

A series of alpha,beta-unsaturated compounds, 1a-c, 9, 13, and 17, were used as reactants in free radical conjugate addition reactions with different radicals generated from alkyl iodides such as 3, 4, or 5 in the presence of triethylborane-oxygen in air or via the use of triethylaluminum-benzoyl peroxide as a free radical initiator. When the reactions were carried out using triethylborane-air, the products, in most cases, were clean and were easily purified. However, higher yields of the 1,4-adducts and less side reactions occurred when less reactive substrates were used as Michael acceptors in reactions with triethylaluminum-benzoyl peroxide and alkyl iodide under similar conditions. A mechanism for this is proposed in Scheme 1.     

1-烷基-3-甲基咪唑溴化盐离子液体的晶体结构及性能

以不同链长溴代烷烃和N-甲基咪唑反应得到1-烷基-3-甲基咪唑溴化盐,用元素分析和核磁共振对化合物进行了表征.室温下用溶剂蒸发法得到了单晶,并用X射线单晶衍射法测定了晶体结构,该晶体属于三斜晶系,空间群为P-1.化合物采用双分子层结构,水分子参与结构的形成,整个化合物由交叉的线性烷基链、咪唑头基、溴离子和水分子组成,溴离子和水分子之间较强的氢键作用在(010)方向上形成了一个无限的O-H···Br氢键链.用偏光显微镜、差示扫描量热(DSC)技术研究了其液晶行为,证明其一水合物为近晶相热致液晶.液晶区域的温度范围较宽说明水分子起到稳定作用.     

Trennung der Rückstoßprodukte von Ra-224- und Cf-252-Quellen durch Bildung von Alkylverbindungen

A new method for the separation of recoil atoms produced by the decay of Ra-224 was developed applying alkyl radicals. Argon was used as carrier gas and the transported alkyl compounds thermally decomposed in front of a GeLi-detector. Under the experimental conditions Pb-212 and Bi-212 could be transported with high yields whereas transport of Tl-208 could not be proved. Their was no interference of the measurements by Rn-220. Using Cf-252 as a source for fission products the recoil atoms were stopped in argon (about 4 atm). The thermalized recoil products were mixed with alkyl radicals and the possibly formed alkyl compounds thermally decomposed in front of a detector. In the experiments with pure argon as inert gas high yields of iodine were found.     

焦脱镁叶绿酸-a甲酯的E-环格氏反应及其脱氧衍生物的合成

以焦脱镁叶绿酸-a甲酯及其3-甲酰甲基为起始原料,通过与直链烷基溴化镁或者环烷基溴化镁进行格氏反应,将131-位羰基转化为烷羟基,经脱水在E-环形成环外碳碳双键,完成单(双)烷亚甲基取代的131-脱氧焦脱镁叶绿酸衍生物的合成,并且讨论了格氏反应的立体化学.所合成的新化合物均经UV,IR,1H NMR及元素分析证明其结构.     

Mass spectra of substituted uracils

The mechanisms for the major fragmentations obtained with selected substituted uracils are discussed. Interpretation of data was facilitated by use of metastable peaks, high-resolution data, and low-voltage spectra. The major fragmentation obtained with N-alkyl substituted uracils, when the alkyl group contains 2 or more carbons, is due to cleavage of the alkyl substituent. This cleavage is accompanied by a rearrangement of 1 or 2 hydrogens from the alkyl group to the uracil ring. Possible mechanisms for the rearrangements are discussed. It was found that the molecular ion of 1- and 3-alkyl substituted uracils (where the alkyl group has 2 or more carbons) does not undergo the expected ‘retro Diels-Alder Reaction’. Instead, the odd-electron ion formed by loss of the alkyl substituent with a single hydrogen rearrangement undergoes this reaction (loses HNCO). Since it is formed as a secondary reaction product, the relative abundance of the ‘retro Diels-Alder’ fragment is low compared to what is obtained in the spectra of the simple uracils. The ‘retro Diels-Alder Reaction’ can be used to differentiate between 2- and 4-thiouracils, and between 1- and 3-methyl and phenyl substituted uracils. It was found that 1- and 3-alkyl substituted uracils (alkyl group of 2 or more carbons) can be differentiated by the mass of the M-alkyl fragment since the 3-substituted compounds give predominantly a double hydrogen rearrangement and the 1-substituted compound gives mainly a single hydrogen rearrangement. In addition the intensity of the molecular ion, relative to the M-alkyl ion, is considerably stronger in the 1-substituted uracils.     

Stereoselective synthesis of 1-nitrobicyclo[3.1.0]hexanes and fused isoxazoline-N-oxides from primary nitro compounds

The one-step preparation of 1-nitrobicyclo[3.1.0]hexane and bicycloisoxazoline-N-oxide was readily achieved from conjugate adducts of nitro alkenes and allylmalonates by treatment with Ag(2)O and iodine under basic conditions. We observed that when a primary alkyl group was present at the β-position of the nitro group, bicyclo[3.1.0]hexane was preferentially formed, whereas if a secondary alkyl group occupied that position, isoxazoline-N-oxide was predominantly produced. High cis-selectivity was observed for the formation of cyclopentane units for both reactions. An iodomethyl adduct, considered an intermediate of the cyclization, was isolated, and its conversion to isoxazoline-N-oxide was successfully achieved. The isoxazoline-N-oxide underwent 1,3-dipolar cycloaddition with alkenes to yield tricycloheterocyclic compounds, which were readily converted to spirolactam in good yield by reductive cleavage of N-O bonds using Raney-Ni. On the other hand, 1,3-dipolar cycloaddition of the isoxazoline-N-oxide to terminal alkynes yielded tricyclic aziridines stereoselectively.     

Highly selective photoreactions of α-oxoamides and α-tropolone alkyl ethers in crystalline inclusion complexes

Control of photocyclization of three α-oxoamides in crystalline inclusion complexes with three kinds of host compounds was studied. In all cases, β-lactams were obtained exclusively. In two cases, cis-β-lactams were formed selectively. By an enantioselective control using an optically active host compound, 1,6-di(o-chlorophenyl)-1,6-diphenylhexa-2, 4-diyne-l,6-diol, optically active β-lactams of high enantiomeric excess were obtained. Irradiation of complexes of α-tropolone alkyl ethers with the above optically active host compound in a solid state, gave the [2+2] photoreaction product, 1-alkoxybicyclo[3.2.0]hepta-3,6-dien-2-one, and its ring-opened derivative, alkyl 4-oxo-2-cyclopentene-1-acetate, in 100 and 72–91% enantiomeric excess, respectively.     

Imidovanadium(v) complexes as reaction partners for kinetically stabilized phosphaalkynes: synthesis of 1,2,4-azaphosphavanada(v)-cyclobutenes, 1,3,5-triphosphabenzenes, and 1H-1,2,4-azadiphospholes

Cycloaddition reactions of the kinetically stabilized phosphaalkynes 1 with the imidovanadium(v) trihalides 9 furnish the 1,2,4-azaphosphavanada(v)cyclobutenes 10. The stability of these novel metallacyclic compounds depends solely on the substitutents of the imido unit. Thus, the imidovanadium(v) species 9 with tertiary alkyl groups on the N atom form stable addition products with 1 while in the cases of compounds 9 with a lower degree of substitution at N (primary and secondary alkyl groups) the primarily formed adducts 10 undergo irreversible decomposition to afford the 1H-1,2,4-azadiphospholes 13. Reactions of an excess of the phosphaaalkyne 1 with the vanadium complexes 9 furnish the corresponding triphosphabenzenes 8 in good yields (36-68%). A catalytic reaction course has been demonstrated for the all-tert-butyl system 1a/9a in which the metallacyclic species 10a serves as the catalytically active species. Poisoning of the catalyst leads to a second reaction pathway, which results in formation of the azatetraphosphaquadricyclanes 16. By means of the stepwise use of different phosphaalkynes 1a,b this methodology provides the first access to the differently substituted triphosphabenzenes through cyclotrimerization.     

Novel nucleophilic substitution of alkyl bromo-2(1H)-pyridones

Nucleophilic substitution of certain alkyl bromo-2(1H)-pyridones gave some unexpected products where the alkyl group is substituted and the ring bromine is replaced by hydrogen. The expected ring substituted product is also formed, but only as the minor product in most cases. Many reactions are cited with various nucleophiles, and a plausible mechanism is also presented.     

Highly Enantioselective Catalytic Hetero-Diels–Alder Reaction with Inverse Electron Demand

Valuable substrates for the synthesis of natural products , compounds 3 (R¹=alkyl, aryl, alkoxy; R², R³=alkyl) are formed from β,γ-unsaturated α-keto esters 1 and vinyl ethers 2 by the title reaction [Eq. (1)]. Copper(II ) bisoxazolines act as catalysts, and in many cases enantiomeric excesses higher than 99.5 % are achieved.     

Thermal decomposition of some perfluoroalkyl grignard reagents. Synthesis of trans-1-halo and trans-1-alkylperfluorovinyl compounds

The thermal decomposition of perfluoroalkyl Grignard reagents (R_fMgX), formed from halogen-metal exchange with alkyl Grignard reagents, provides a good synthetic route to trans-1-haloperfluorovinyl compounds.

The decomposition of R_fMgX (where X = Cl, Br, I) in the presence of RMgX generally leads to a mixture of trans-1-alkylperfluorovinyl and trans-1-haloperfluorovinyl compounds. However, the choice of RMgX with respect to both the alkyl group and halogen is critical as regards the formation of the trans-1-alkylperfluorovinyl compounds.Several possible mechanisms are suggested to account for the experimental observations.     

Clathrate and Inclusion Compounds. Part 13 [1]. Vibrational and NMR Spectroscopic Studies of Carboxylic Acid Guests in Urea

Infrared, Raman and solid state¹³C NMR spectra have been recorded for arange of inclusion compounds of urea containingstraight chain aliphatic carboxylic acids(butyric – decanoic) as guests. Inclusioncompounds are not formed with formic, acetic andpropionic acids. Thiourea does not forminclusion compounds with any of the C1 to C10acids. The vibrational and NMR data support theconclusion that the acids are present ashydrogen bonded dimers in the channels of thehost. The alkyl chain ¹³C chemical shiftvalues are very different from those of acidguests in the cavities formed in Dianin'scompound. These suggest that the alkyl chainsare present in the all-trans conformation,although weak bands observed in the spectrum ofthe decanoic acid inclusion compound lend somesupport to suggestions based on MM calculationsthat other conformations might be present.     

Triphenylphosphine-m-sulfonate/carbon tetrabromide as an easily recoverable catalyst system for the efficient synthesis of xanthene and xanthenone derivatives under solvent-free conditions

A solid complex,readily prepared from commercially available sodium triphenylphosphine-m-sulfonate（TPPMS） and carbon tetrabromide,can be used as an easily recoverable and reusable catalyst system for one-pot condensation of 2-naphthol with aldehydes to construct 14-aryl（alkyl）-14H-dibenzo[a j]-xanthene derivatives and one-pot condensation of 2-naphthol with aldehydes and cyclic 1 3-dicarbonyl compounds to construct 12-aryl（alkyl）-8 9 10 12-tetrahydrobenzo[a]xanthen-11-one derivatives.     

An efficient strategy for N-alkylation of benzimidazoles/imidazoles in SDS-aqueous basic medium and N-alkylation induced ring opening of benzimidazoles

A sustainable route for the N-1 alkylation of imidazole and benzimidazole derivatives has been developed under volatile organic solvent free condition in alkaline water-SDS system. Incorporation of SDS in the reaction medium enhances the reaction rate by suppressing the solubility issue that arises for different substrates. This method provides high yield of the alkylated product in a shorter reaction time. For reactive alkyl halides reaction proceeds at ambient temperature whereas in the cases of less reactive alkyl halides require 55–60?°C to complete alkylation process. N-alkylation induced ring opening of the heterocyclic ring in benzimidazole derivatives to multifunctional aromatic compounds were noticed at 60?°C when more than two equivalents of alkyl halide was used.     

Synthetic transformations of 1-cyanomethylbenzotriazole

Lithiation of 1-cyanomethylbenzotriazole ( 4 ) with LDA and subsequent reactions with alkyl halides or carbonyl compounds afforded the corresponding 1-(α-cyanoalkyl)- and 1-(α-cyanoalkenyl)-benzotriazoles. Bromination of 4 with NBS formed 1-(bromocyanomethyl)benzotriazole. 1-Cyanoalkylbenzotriazoles condensed with hydrazine hydrate to give 4-amino-3,5-bis(benzotriazol-1-yl)triazoles which underwent deamination with sodium nitrite to yield 3,5-bis(benzotriazol-1-yl)triazoles.     

Pinacol Rearrangement of 3,4‐Dihydro‐3,4‐dihydroxyquinolin‐2(1H)‐ones: An Alternative Pathway to Viridicatin Alkaloids and Their Analogs

3‐Alkyl/aryl‐3‐hydroxyquinoline‐2,4‐diones were reduced with NaBH₄ to give cis‐3‐alkyl/aryl‐3,4‐dihydro‐3,4‐dihydroxyquinolin‐2(1H)‐ones. These compounds were subjected to pinacol rearrangement by treatment with concentrated H₂SO₄, resulting in 4‐alkyl/aryl‐3‐hydroxyquinolin‐2(1H)‐ones. When a benzyl (Bn) group was present in position 3 of the starting compound, its elimination occurred during the rearrangement, and the corresponding 3‐hydroxyquinolin‐2(1H)‐one was formed. The reaction mechanisms are discussed for all transformations. All compounds were characterized by IR, ¹H‐ and ¹³C‐NMR spectroscopy, as well as mass spectrometry.     

Ion-selective electrodes in titrations involving azo-coupling reactions: Part 2. Titrations with diazonium salts derived from 1-aminonaphthalenes and 1-amino-9,10-anthraquinone

Lipophilic arenediazonium salts dreived from 1-aminonaphthalene, 1-amino-4-bromonaphthalene, 1-amino-4-nitronaphthalene and 1-amino-9,10-anthraquinone were tested as titrants for determination of aromatic hydroxy compounds, amines, and compounds containing active methylene groups, usually at the 10^?2 M level. The potentiometric titrations were monitored with indicator electrodes selective for organic cations which were based on PVC membranes plasticized with 2-nitrophenyl alkyl ethers (where alkyl is n-octyl or 2-ethylhexyl). Titrations of 11 compounds ranging from 1,2-diaminotoluene to 1-phenyl-3-methyl-5-pyrazolone were examined; 4-bromo-1-naphthalenediazonium chloride seemed to be the most widely applicable titrant.     

13C chemical shift subsitituent parameters for alkyllithium compounds in hydrocarbon solvents

¹³C chemical shift substituent parameters are presented for carbons α, β, γ, and δ to the lithium atom based on the chemical shifts of 14 ⁶Li-enriched alkyllithium compounds. The chemical shift of the carbon α to lithium depends on the branching of alkyl group at the α-carbon and on the aggregation state of the alkyllithium compound. Increased branching results in increased upfield shifts. This is interpreted in terms of the varying electronic nature of the alkyllithium compounds. The chemical shift of the carbon β to lithium substitution is shifted downfield approximately 5 ppm from the corresponding carbon in the parent hydrocarbon, irregardless of the alkyl group or the aggregation state of the alkyllithium compound. The chemical shift of the γ-carbon depends on the steric requirements of the alkyl group. Carbons four or more bonds from lithium have the same chemical shift as those of the parent hydrocarbon. The derived chemical shift parameters are used to assign the α-carbons of two alkyllithium compounds formed from the reaction of t-butyllithium and trimethylvinylsilane.