Dimethyl Acetylenedicarboxylate in Reactions with Substituted 3‐(2‐aminophenyl)‐6‐R1‐1,2,4‐triazin‐5‐(2H)‐ones: Structure and Properties of the Products

The article describes unusual [5 + 1]‐cyclocondensations of dimethyl acetylenedicarboxylate (DMAD), in which this reagent uncharacteristically acts as a 1,1‐biselelectrophilic agent. Reactions of DMAD with 1,5‐bisnucleophilic 3‐(2‐aminophenyl)‐6‐R¹‐1,2,4‐triazin‐5(2H)‐ones yielded triazinoquinazoline‐derived diesters. The latter was shown to react with nucleophiles: hydrazine cleaved the pyrimidine ring of the diesters to give anilines, while ester hydrolysis furnished corresponding carboxylic acids.     

Absolute configuration of 1,n-diols by NMR: the importance of the combined anisotropic effects in bis-arylmethoxyacetates

The absolute configuration of a 1,n-diol can be assigned from the (1)H NMR spectra of its (R)- and (S)-AMAA diesters if the chemical shifts are interpreted as the result of the joint action of the two chiral auxiliaries.     

油酸乙二醇酯添加剂中双酯组成的气相色谱-质谱分析

用硅胶玻璃色谱柱吸附样品 ,采用溶剂梯度洗脱的方法从油酸乙二醇酯添加剂中分离出乙二醇双酯 ,再用GC -MS详细地分析了乙二醇双酯的组分 ,给出了分析乙二醇双酯的优化条件 ,并通过乙二醇双酯的组分推断出油酸原料中所含酸的种类。     

A mechanistic study of the alkaline hydrolysis of diaryl sulfate diesters

Nearly all of the reported studies of reactions of sulfate diesters are for dialkyl or alkyl aryl diesters, which undergo reaction by carbon-oxygen bond fission. Sulfuryl transfer reactions of sulfate diesters (RO-SO(2)-OR') proceeding by attack at sulfur have been little explored. When both ester groups are aryl groups the hydrolysis reaction (sulfuryl transfer to water) occurs by way of attack at sulfur. The alkaline hydrolysis of diaryl sulfate diesters was shown to obey first-order kinetics with respect to [(-)OH] and proceed through S-O bond fission, in a mechanism that is most likely concerted. Activation parameters for 4-chloro-3-nitrophenyl phenyl sulfate and 4-nitrophenyl phenyl sulfate gave the following respective values: Delta H(++) = 88.0 +/- 0.1 and 84.83 +/- 0.06 kJ mol(-)(1) and Delta S(++) = -37 +/- 1 and -50.2 +/- 0.5 J mol(-)(1) deg(-)(1). The dependence of the second-order rate constant for hydrolysis on leaving group pK(a) was analyzed giving a beta(lg) slope of -0.7 +/- 0.2 and a Leffler alpha parameter value of 0.36. A (15)k kinetic isotope effect (KIE) for the hydroxide attack on 4-nitrophenyl phenyl sulfate of 1.0000 +/-0.0005 and an (18)k(lg) KIE value of 1.003+/-0.002 were obtained.     

支链淀粉-三(苯基氨基甲酸酯)手性固定相的制备及酸性外消旋药物联苯双酯的拆分

合成并制备了支链淀粉－三（苯基氨基甲酸酯）手性固定相，利用高效液相色谱首次拆分了酸性外消旋药物联苯双酯，考察了流动相中异丙醇含量对拆分的影响。     

Multiscale Porosity from Thermoreversible Poly(vinylidene fluoride) Gels in Diethyl Azelate

Poly(vinylidene fluoride) (PVF₂) produces thermoreversible gels in a series of diesters. The polymer-solvent complexation occurred for intermittent number of carbon atoms n ⩾ 2 and the enthalpy of complexation increased with increasing n. The gels were dried by replacing the diesters with low boiling solvent like cyclohexane (bp. 80 °C) and methylcyclohexane (bp. 99 °C). The porosity of the dried gels was measured using Poremaster-60. For PVF₂-DEAZ gel meso and macro porosity have been observed. The former pore dimensions have been attributed for polymer-solvent complexation while the macroporosity has been attributed for caging of solvent between the PVF₂ fibrils The porosity measured from nitrogen adsorption isotherms using BJH method indicate presence of minimum pore diameter of 3.8 nm for the 10% dried gel of PVF₂.     

Synthesis and structure of pyrazolo[5,1-a]isoindol-8-ones from Aromatic Ortho Diesters

The title compounds 2 , have now been shown to arise in certain cases from condensation of aromatic ortho-diesters with ketone, where formerly only indeno[1,2-c]pyrazol-4(1H)-ones 3 have been reported from such reaction. Heretofore 2 was obtained in a less direct fashion from phthalaldehydic acid esters. When hetero-aromatic diesters were employed, new heterocyclic ring systems as represented by 2a,b ,c were prepared for the first time. Structures of 2 have been verified from detailed ¹H and ¹³C nmr studies, while representative intermediates 4–9 in the condensation of diesters to 2 have been isolated and identified.     

Triphenylantimony diester preparation

A series of triphenylantimony diesters of monocarboxylic acids has been prepared in a simple way by reacting triphenylantimony oxide with the corresponding acids in methanol. The antimony content was determined in the obtained compounds and the ¹H NMR spectra were measured.     

Novel approaches to analysis of 3-chloropropane-1,2-diol esters in vegetable oils

A sensitive and accurate method utilizing ultra-high performance liquid chromatography (U-HPLC) coupled to high resolution mass spectrometry based on orbitrap technology (orbitrapMS) for the analysis of nine 3-chloropropane-1,2-diol (3-MCPD) diesters in vegetable oils was developed. To remove the interfering triacylglycerols that induce strong matrix effects, a clean-up step on silica gel column was used. The quantitative analysis was performed with the use of deuterium-labeled internal standards. The lowest calibration levels estimated for the respective analytes ranged from 2 to 5 μg kg⁻¹. Good recovery values (89–120%) and repeatability (RSD 5–9%) was obtained at spiking levels of 2 and 10 mg kg⁻¹. As an alternative, a novel ambient desorption ionization technique, direct analysis in real time (DART), hyphenated with orbitrapMS, was employed for no separation, high-throughput, semi-quantitative screening of 3-MCPD diesters in samples obtained by chromatographic fractionation. Additionally, the levels of 3-MCPD diesters measured in real-life vegetable oil samples (palm oil, sunflower oil, rapeseed oil) using both methods are reported. Relatively good agreement of the data generated by U-HPLC-orbitrapMS and DART-orbitrapMS were observed. With regard to a low ionization yield achieved for 3-MCPD monoesters, the methods presented in this paper were not yet applicable for the analysis of these contaminants at the naturally occurring levels.     

Factors Influencing the Course of the Macrocyclization of α,ω‐Diamines with Esters of α,ω‐Dicarboxylic Acids

The efficient synthesis of eight new macrocyclic amides (lactams) via reaction of diesters with diamines under normal dilution conditions is described. The role of intermolecular H‐bond formation and steric hindrance is discussed based on ¹H‐ and ¹⁵N‐NMR studies of appropriate model compounds. Principles for the optimal choice of esters that can be efficiently transformed into diamides have been developed.     

Copper(I)-catalyzed [2 + 2] photocycloadditions with tethered linkers: synthesis of syn-photodimers of dicyclopentadienes.

Cu(I)-catalyzed intramolecular photocycloadditions of diesters made of endo-dicyclopentadiene derivatives linked by the ester bonds with tethers are highly regio- and stereoselective and complete within hours, and the tethers can be easily cleaved afterward upon reduction with LiAlH4-Irradiation of the diesters afforded a 1:1 mixture of the heretofore unknown exo-cis-exo dimer, originating from the (R,S/S,R) diastereomer of the diester and the exo-trans-exo, deriving from the (R,R/S,S) diastereomer. The intermolecular photodimerization yielded, instead, only exo-trans-exo isomers and side products after irradiation for several days. The role of the tether's length and structure on the course of the photocycloadditions was investigated, and it was observed that short tethers introduce considerable strain in the products' framework. Adamantyl-containing tethers provided the shortest reaction times and highest yields. X-ray diffraction analysis of an exo-cis-exo stereoisomer containing adamantane in the tether exhibited an unusually close approach between H atoms on the methylene bridges and a long C-C distance in the cyclobutane ring. A rearrangement induced by X-ray irradiation was observed in this molecule.     

Features of reactions of phthalic anhydride with polyfluorinated alcohols

Polyifluoroalkyl mono- and diesters of phthalic acid were obtained by the reaction of phthalic anhydride with polyfluorinated alcohols. The structure of the polyfluoroalkyl phthalates was studied using IR and ¹H, ¹³C NMR spectroscopy. The nature of the associative interactions between cyclohexanone and polyfluorinated alcohols was revealed.     

The Synthesis and Mechanistic Considerations of a Series of Ammonium Monosubstituted H-Phosphonate Salts

A series of ammonium monosubstituted H-phosphonate salts were synthesized by combining H-phosphonate diesters with amines in the absence of solvent at 80 °C. Variation of the ester substituent and amine produced a range of ionic liquids with low melting points. The products and by-products were analyzed by spectroscopic and spectrometric techniques in order to get a better mechanistic picture of the dealkylation and formal dearylation observed. For dialkyl H-phosphonate diesters, (RO)₂P(O)H (R=alkyl), the reaction proceeds via direct dealkylation with the reactivity increasing in the order R=iPr<Et<Me corresponding to DFT calculated activation enthalpies of 22.6, 20.8, and 17.9 kcal mol⁻¹. For the diphenyl H-phosphonate diesters, (PhO)₂P(O)H, the dearylation was found to proceed via phenol-assisted formation of a 5-coordinate intermediate, (PhO)₃PH(OH), from which P(OPh)₃ and water were eliminated. The presence of an equivalent of water then facilitated the formation of P(OH)₂OPh and the amine, R'NH₂, subsequently abstracted a proton from it to yield [(PhO)PH(O)O]^-[R'NH₃]⁺.     

On the assignment of the absolute configuration at the isolated methyl branch in miyakosyne A,cytotoxic linear acetylene,from the deep-sea marine sponge Petrosia sp.

Absolute configuration of miyakosyne A at its isolated branched methyl stereogenic center has been studied by chemical degradation in combination with esterification with the Ohrui's acid. Comparison of the ¹H NMR data of the relevant diesters for the degradation product and the synthetic standards indicated the 14R-configuration.     

Syntheses of stereoregular and optically active polyamides from active 4-chloro-1-benzotriazolyl diesters and diamines

A new route to prepare optically active polyamides was established, based on the polycondensation of two new active diesters: the active diesters of 4-chloro-1 hydroxybenzotriazole, such as 1,1'-(terephthaloyldioxy)bis(4-chloro-benzotriazole), and 1,1'-(isophthaloyldioxy)bis(4-chlorobenzotriazole), with optically active isomers of 2,4-diaminopentane. Dipolar aprotic solvents such as N,N-dimethylformamide and dimethyl sulfoxide were used as reaction solvents. The solution polycondensation carried out in solution at room temperature afforded optically active polyamides. The aminolysis of the two active diesters was carried out as a model reaction study.     

Pyrroloindoles. 17. Synthesis and condensation reactions of benzo[e]pyrrolo[3,2-g]indole-2,9-dicarboxylic acid dichloride

1H, 10H-benzo[e]pyrrolo[3,2-g]indole-2,9-dicarboxylic acid dichloride has been synthesized and condensed with amines and phenols to give the corresponding diamides and activated diesters. The mass spectra of the dichloride and several diamides have been investigated.For Communication 16 see [1].Iv. Dzhavakhishvili State University, Tbilisi 380028, Georgia. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 942–948, July, 1998.     

Esters of pyromellitic acid. Part II. Esters of chiral alcohols: para pyromellitate diesters as a novel class of resolving agents and use of pyromellitates as duplicands for chiral purification

Methods are presented for the preparation of pyromellitate esters of chiral terpene alcohols, including d- (3) or l-menthol (4), d-isomenthol (7), l-borneol (8), or d- (5) or l-isopinocampheol (6). Alcoholysis of PMDA in CH2Cl2/Et3N led to the formation of monoesters (e.g., 18) or diesters (11, 12), as needed, relying on the differential reactivity of the two anhydride groups. The easily isolated para diester (11) crystallized before the meta diester (12) from HOAc. Nicotine (1, 14) was efficiently resolved as 1:1 salts with the menthyl (11a, 11b) or bornyl (11f) para diesters, prototypes of what promises to be a large class of novel resolving agents. Recrystallization of para-di-d-menthyl pyromellitate (11a) greatly improved the chiral purity of the contained d-menthol (3), an example of purification by "duplication". An alternative synthesis of specific diesters took advantage of the easily separated benzyl diesters and their derived acid chlorides (19, 21), with the benzyl esters serving as temporary blocking groups removable by catalytic hydrogenolysis. Pyromellitate tetraesters (26) were prepared by base-catalyzed transesterification of the tetraethyl ester (25). Tri- l-menthyl pyromellitate (27b) was obtained by catalytic hydrogenolysis of benzyl tri-l-menthyl pyromellitate (31b), itself prepared from the alcoholysis of benzyl pyromellitate triacid chloride (30) with l-menthol (4).     

Thermochemical Reactions of H Complexes

Thermal reactions of H complexes formed by methyl and ethyl diesters of aromatic tetracarboxylic acids with diamines were studied by thermal analysis. Some kinetic parameters of formation and degradation of polyimides during thermolysis in the self-generated atmosphere were determined.     

Separation of geometric isomers of native lutein diesters in marigold (Tagetes erecta L.) by high-performance liquid chromatography-mass spectrometry

Lutein is found in many foods; the richest and purest plant source is marigold flower (Tagetes erecta L.). In this plant, lutein is in the form of saturated fatty acid diesters. By using a binary mobile phase consisting of ethyl acetate and acetonitrile-methanol (9:1), improved separation was achieved on a C18-bonded phase. The unique absorption of lutein cis isomers at 330nm was used in combination with MS to identify the novel cis-lutein isomeric dimyristate, myristate-palmitate, dipalmitate, and palmitate-stearate diesters, as well as the rare combinations of both trans- and cis-lutein laurate-palmitate and trans- and cis-lutein myristate-stearate. The presence of the all-trans-lutein laurate-myristate, dimyristate, myristate-palmitate, palmitate-stearate, and distearate diesters, reported by others, was also confirmed.