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The chiral oxazolidine moiety is an important core in asymmetric synthesis due to its ability to participate in various stereoselective chemical reactions and because it forms part of more complex and important active compounds. Therefore, in this letter we report a convenient diastereoselective and practical strategy for the synthesis of chiral methyl 2-((4R)-3-acryloyl-4-phenyloxazolidin-2-yl)acetates, starting from (R)-(–)-2-phenylglycinol and methyl propiolate, which were obtained via two simple chemical and stereoselective reactions. [ABSTRACT FROM AUTHOR]

Previously unknown C-19 lappaconitine derivatives were prepared via [3 + 2] cycloaddition reactions of a nitrone based on lappaconitine with compounds containing a triple bond, i.e., propargyl alcohol, methyl propiolate, phenylacetylene, 3-phenoxypropyne-1, and propargyl aldehyde diethylacetal. [ABSTRACT FROM AUTHOR]

[Display omitted] An N , N -bis(p -methoxybenzyl)-protected α-acetyl-α-diazo-methane sulfonamide proved to be a useful building block for accessing new 5-methyl-1,2,3-thiadiazole-4-sulfonamide as well as methyl 3-sulfamoyl-1 H -pyrazole-5-carboxylate. The latter was further subjected to N -alkylation and N -arylation reactions. All resulting compounds showed potent inhibition of I, II and particularly of cancer-related IX and XII isoforms of human carbonic anhydrase. [ABSTRACT FROM AUTHOR]

The reaction of ethyl anthranilate with DMAD and with methyl propiolate in dichloromethane in the presence of ethylaluminium dichloride as catalyst at room temperature gives a mixture of the respective E- and Z-intermediate derivatives which do not cyclize even on refluxing for several hours. On carrying out the reaction in refluxing methanol in the absence of the catalyst, only one stereochemical isomer is obtained which is Z-intermediate indicating conversion of less stable isomer into the thermodynamically more stable derivative under these conditions. The resulting product did not cyclize even on refluxing in methanol in the presence of montmorillonite K10 clay catalyst. The reaction of phenyl monothioanthranilate with DMAD and with methyl propiolate gives similar results. A theoretical investigation of the reaction of ethyl anthranilate with methyl propiolate at the B3LYP/6-31 + G(d) level reveals that it occurs in five steps. [ABSTRACT FROM AUTHOR]

Double Mannich bases obtained from α-indanone and α-tetralone contain a bis-β-amino ketone fragment and are promising intermediate compounds for the synthesis of nitrogen heterocycles via reactions with dimethyl acetylenedicarboxylate and methyl propiolate. The products of these reactions are determined by the activated acetylene structure. The reaction begins with attack of the activated acetylenic compound on the tertiary nitrogen atom of the Mannich base to give 1,3-zwitterionic intermediate. The subsequent domino reaction is driven by neutralization of the charge on the nitrogen atom through formation and/or rupture of several C–C bonds. Intramolecular attack of the negatively charged center of the 1,3-zwitterion derived from the indanone base and dimethyl acetylenedicarboxylate on the carbonyl carbon atom of the indanone fragment is followed by domino process, leading to the formation of dimethyl 2-methyl-1,2-dihydro-9H-indeno[2,1-c]-pyridine-3,4-dicarboxylate. The reaction of the same Mannich base with methyl propiolate involves 1,3-sigma-tropic rearrangement with neutralization of the positive charge on the nitrogen atom in the intermediate structure and negative charge transfer to the carbonyl oxygen atom. Next follows aldolization/crotonization with the second β-amino carbonyl fragment to produce methyl 2′-methyl-1-oxo-1,1′,2′,3,5′,11′-hexahydrospiro-[indene-2,6′-indeno[2,1-c]azocine]-4′-carboxylate. One more reaction direction leading to the formation of linear enamines via intramolecular proton migration from the indan fragment to the C-anionic center in the 1,3-zwitterion with simultaneous elimination of 2-methylideneindan-1-one has been revealed by HPLC/MS analysis of both reaction mixtures. Such enamines, methyl 3-{methyl[(1-oxo-1,2,3,4-tetrahydronaphthalen-2-yl)methyl]amino}prop-2-enoate and dimethyl (2Z)-2-{methyl[(1-oxo-1,2,3,4-tetrahydronaphthalen-2-yl)-methyl]amino}but-2-enedioate, were isolated in the reactions of activated acetylenic compounds with the Mannich base derived from tetralone. Previously described synthesis of 1-azabicyclo[3.3.1]nonanes from Mannich bases has been reproduced, and detailed analysis of the reaction mixtures has revealed products resulting from elimination of one alkylaryl group from the zwitterionic intermediate. The formation of linear enamines, dimethyl (2Z)-2-[methyl(3-oxo-3-phenylpropyl)amino]but-2-enedioate and dimethyl (2Z)-2-{methyl-[3-oxo-3-(thiophen-2-yl)propyl]amino}but-2-enediate, suggests facile retro-aldol reaction of 3-aroyl-4-aryl-1-methylpiperidin-4-ols as the necessary step. PASS online predicted diverse biological activities of all newly synthesized compounds with a probability of 65–80%. [ABSTRACT FROM AUTHOR]

Selected hetaryl and aryl thioketones react with acetylenecarboxylates under thermal conditions in the presence of LiClO4 or, alternatively, under high-pressure conditions (5 kbar) at room temperature yielding thiopyran derivatives. The hetero-Diels–Alder reaction occurs in a chemo- and regioselective manner. The initially formed [4 + 2] cycloadducts rearrange via a 1,3-hydrogen shift sequence to give the final products. The latter were smoothly oxidized by treatment with mCPBA to the corresponding sulfones.

Transformations of 2-methyl-1-phenylethynyl-1,2,3,4-tetrahydroisoquinoline resulting from the action of activated alkynes in trifluoroethanol and hexafluoroisopropanol were studied. In reactions with dimethyl acetylenedicarboxylate, 6-phenylethynyl-substituted benzazocines were prepared, while methyl 4-benzyl-5-(2-ethenylphenyl)-1-methyl-1H-pyrrole-3-carboxylate and benzo[d][3]-azacyclodeca[4,6,7]triene with the allene fragment, respectively, were isolated in reactions with methyl propiolate and acetylacetylene in addition to the corresponding benzazocines. As a rule, in hexafluoroisopropanol, the yields of azocines are higher. In reaction with acetylacetylene in dichloromethane, 1-(2-acetylvinyl)-1-phenylethynyltetrahydroisoquinoline is formed in high yield. [ABSTRACT FROM AUTHOR]

A metal-free highly efficient synthesis of a wide range of 4-propenyl 1,4-DHPs from pyridines, methyl propiolate, and aromatic acids is described. The reactions are conducted under convenient conditions and provide products with excellent regioselectivity in good to excellent yields, with broad substrate scope. [ABSTRACT FROM AUTHOR]

1-Tetrazolyl-substituted tetrahydro-β-carbolines undergo a reaction with activated alkynes (acetylacetylene, methyl propiolate, and dimethyl acetylenedicarboxylate) over 4-8 days in MeOH or 1 day in CF3CH2OH with the formation of multicomponent mixtures, from which spiro[indole-3,4'-pyridines] were isolated chromatographically. Additionally, two azocino[5,4- b]indoles were isolated from methyl propiolate and acetylacetylene reactions. [ABSTRACT FROM AUTHOR]

Base-catalyzed domino reaction between N -methylisatin and methyl propiolate afforded four diastereomeric dispiro-1,3-dioxolane bisoxindoles. The reaction mechanism involved sequential 1,2-addition of acetylide anion to the carbonyl group of isatin, 1,2-addition of the resulting oxyanion to a second molecule of isatin, and the final 5- exo - dig cyclization process. [ABSTRACT FROM AUTHOR]

[Figure not available: see fulltext.] Three-component reactions of cotarnine chloride with silver acetylides and methyl propiolate or ethynyl methyl ketone in acetonitrile, as well as two-component reactions of 5-phenylethynyl-substituted tetrahydro[1,3]dioxolo[4,5- g]isoquinoline with alkynes in various solvents were studied. Performing them in 2,2,2-trifluoroethanol as the solvent, 10-phenylethynyl-substituted tetrahydro[1,3]dioxolo[4,5- i]-[3]benzazocines were obtained in good yields. [ABSTRACT FROM AUTHOR]

A novel HPLC method has been established for the determination of thiols in fruit samples, introducing, for the first time, methyl propiolate as an advantageous precolumn derivatization reagent for cysteine (CYS), glutathione (GSH), and N-acetylcysteine (NAC). The formed derivatives were detected at 285 nm, following isocratic separation on a core-shell column (Ascentis Express C18, 50 × 2.1 mm i.d., 2.7 μm) with a mobile phase of 15 mmol L (ΝΗ)ΗPO/HPO (pH = 2.2)/methanol (92:8 v/ v), containing 1 mmol L EDTA, at a flow rate of 0.2 mL min. Derivatization parameters were optimized including pH and concentration of buffering medium, amount concentration of methyl propiolate, derivatization time, and temperature, by the univariate approach. Under optimal conditions, the developed analytical scheme offers a total analysis time of less than 10 min, limits of detection in the range 0.1-0.5 μmol L, and satisfactory linearity up to 100 μmol L for all analytes. The method proved also to be equally selective and robust. Endogenous thiols were determined in melon, watermelon, and avocado, using the standards addition approach, after minimal sample preparation, with no use of organic solvents. The accuracy was evaluated by recovery experiments resulting in the range of 86.4-118.5 %. [ABSTRACT FROM AUTHOR]

[Figure not available: see fulltext.] Three-component reactions of tetrahydropyrrolo[1,2- a][1,4]benzodiazepines with methyl propiolate or acetylacetylene and СН, NH, SH, and ОН acids were studied in various solvents. The reaction direction is assumed to depend on the nucleophilicity of anion, formed through deprotonation of acid by the anionic center of initial Michael-type zwitterion. [ABSTRACT FROM AUTHOR]

A novel method for the assembly of multisubstitued dihydropyridines has been developed starting from methyl propiolate and propargylamines. The reactions were efficiently catalyzed by AuPPh3Cl to get high regioselectivity and high yields. And alternatively, since propargylamines could be easily derived by the CuCl-mediated addition of methyl propiolate to imines, the reactions could be carried out as a sequential three-component model. [ABSTRACT FROM AUTHOR]

[Figure not available: see fulltext.] 2-(Chloromethyl)-5,6,7,8-tetrahydropyrido[4',3':4,5]thieno[2,3- d]pyrimidin-4(3 Н)-ones reacted with acetylenedicarboxylate ester, methyl propiolate or acetylacetylene, forming mixtures of 2-(chloromethyl)-5,6,7,10-tetrahydropyrimido[5',4':4,5]thieno[3,2- d]azocin-4(3 Н)-ones and 2'-chloromethyl-6'-methylidene-2,3-dihydro-1 Н-spiro[pyrido[4,5']thieno[2,3- d]pyrimidin]-4'(3' H)-ones in various ratios. Analogous products were also obtained in the reaction of 2-(methoxymethyl) derivative with methyl propiolate, while using 2-[(morpholin-4-yl)-methyl] derivative in a similar reaction led to the formation of a more complex product mixture. [ABSTRACT FROM AUTHOR]

Highlights: [•] Methylpropiolate for derivatization of thiols in CE. [•] First application of methylpropiolate in CE. [•] Determination of glutathione in baker's yeasts. [ABSTRACT FROM AUTHOR]

In the present study, we report a new method for the determination of two primary thiols, cysteine ( CYS) and glutathione ( GSH), by hydrophilic interaction LC. The polar analytes are separated isocratically using a mobile phase consisting of 65% acetonitrile/35% ammonium acetate (15 mmol/L, pH 2.0) and are detected at 285 nm following on-line postcolumn derivatization by the thiol-selective reagent methyl propiolate. The main figures of merit included linearity in the range of 5-200 μmol/L and an LOD 0.6 μmol/L for both compounds. The absence of matrix effect allowed the determination of CYS and GSH in various yeast samples. GSH was present in most of the samples at levels ranging between 0.9 and 3.1 mg/g, whereas CYS was determined in only one sample at a significantly lower concentration. In terms of accuracy, the percent recoveries ranged between 91.2 and 105.6% for GSH, and 91.6 and 106.9% for CYS. [ABSTRACT FROM AUTHOR]

Abstract: The reactions of methyl propiolate and ethyl buta-2,3-dienoate with cyclohexanone induced by SmI2 occurred either at α- or β-position to yield different products depending on with or without a proton source. The synthesis of terpenic acid was demonstrated using this reaction. [Copyright &y& Elsevier]

Three-component reactions involving azaarenes (quinoline, isoquinoline, and phenanthridine) with acetylenic esters such as methyl propiolate or ethyl propiolate in the presence of NH-heterocyclic compounds (carbazole, maleimide, 5-nitroindazole, 2-benzoxazolinone, indole, and 2-methylindole) or 1,3-dicarbonyl compounds involving acetylacetone and N,N′-dimethylbar bituric acid are described. The reactions proceeded smoothly at room temperature without a catalyst and with excellent yields. This method is very useful for functionalizing aza-aromatic compounds in a one-pot operation. [ABSTRACT FROM AUTHOR]

Iodide complexes of Pt in acetone solution react with an excess of CHI and the stoichiometric amount of methyl propiolate (MP) by oxidative addition of CHI and iodoplatination of the triple bond of the alkyne with the formation of [InlineMediaObject not available: see fulltext.]. The regioselectivity of iodoplatination here formally contradicts the Markovnikov rule; the Pt atom forms a σ bond with the terminal C atom of the initial alkyne. With an excess of the MP reversible iodoplatination of a second molecule of the alkyne occurs with the formation of a methyl-divinyl derivative of Pt. The addition of the second molecule of the alkyne to Pt atom occurs in accordance with the Markovnikov rule at the more electron-saturated internal carbon atom. [ABSTRACT FROM AUTHOR]

In this study, a new, green analytical method is proposed for the determination of N-acetylcysteine (NAC) in pharmaceutical formulations. The analyte was separated from the samples matrix using a 100% aqueous mobile phase [0.05% v/v CH3COOH+1 mmol L−1 ethylenediaminetetraacetic acid (EDTA) in water] and a suitable analytical column (Prevail reversed phase column). Detection was carried out at 285nm after on-line post-column derivatization (PCD) with methyl-propiolate (MP) in alkaline medium. Method development included both chromatographic and reaction parameters, while validation was based on international recommendations. The developed analytical scheme excludes the use of organic modifiers from all steps of pretreatment/analysis and offers adequate figures of merit for the quality control (assay and content uniformity) of NAC-containing formulations. [ABSTRACT FROM AUTHOR]

Abstract: Pentathiepinopyrroles reacted with methyl propiolate and triphenylphosphine to give regioselectively dithiinopyrroles in agreement with the electron distribution in the proposed reaction intermediate. Thieno[2,3-f][1,2,3,4,5]pentathiepin when treated with methyl propiolate and triphenylphosphine gave a pair of regioisomers where the higher yielding regioisomer contained the same mode of junction as in the case of pentathiepinopyrroles. X-ray crystal structures are provided for the thieno[2,3-b][1,4]dithiine carboxylate isomers. Quantum-chemical calculations B3LYP/6-31G(d) and B3LYP/6-311++G(d,p) have been carried out for better understanding of the reaction mechanisms; the index of synchronism of the S h addition and the index of a relative difference in bond orders in transition states are in good agreement with the formation of the regioisomers by the reaction of unsymmetrical pentathiepins with alkynes containing one electron-withdrawing group. [Copyright &y& Elsevier]

For the first time, a novel, simple, and highly efficient synthesis of N-aryl-N-[1,3]thiazino[3,4a][1,3]benzimidazol-1-ylidenamines is presented. The one-pot reaction of o-phenylenediamine, aryl isothiocyanate, and methyl acetylenecarboxylate proceeds in toluene-dichloromethane without any catalyst under reflux conditions to produce the title compounds in 60-70% yield. From a mechanistic point of view, the reaction is proposed to occur via two cyclizations and four heteroatom-carbon bond formations. [ABSTRACT FROM AUTHOR]

A novel [Cu(OH)˙TMEDA]2Cl2 catalyzed tandem reaction has been developed for the synthesis of a series of sterically and electronically divergent phenacyl tertiary phosphine-boranes. [ABSTRACT FROM AUTHOR]

Abstract: The reaction conditions for the Pd-catalyzed cyclization reaction of 2-(2-carbomethoxyethynyl)aniline derivatives were investigated. The amounts of Pd(PPh3)4, methyl propiolate, and ZnBr2 could be significantly reduced compared with those reported in our preliminary publication by careful tuning of the solvent and the reaction temperature. In addition to the above results, formal syntheses of pyrroloquinoline quinone (PQQ) and its analogue from 2-amino-5-nitrophenol using a Pd-complex-catalyzed sequential coupling-cyclization reaction between methyl propiolate and 2-iodoaniline derivatives are described. [Copyright &y& Elsevier]

The reactions of arylaldehydes with 3-butyn-2-one, methyl propiolate or propynenitrile in the presence of Lewis acids such as titanium(IV) bromide (TiBr4) or boron(III) tribromide (BBr3) (1.4 equiv.) can be drastically affected by the reaction temperature. When the reaction of arylaldehydes with 3-butyn-2-one was carried out at <−20°C, brominated compounds were obtained as the major product. However, when the reaction was carried out at room temperature (20°C), both the brominated compounds and α,β-dibrominated compounds were formed as the major products. Moreover, at 70°C in 1,2-dichloroethane, the α,β-dibrominated compounds were obtained as the sole products. On the other hand, the reactions of arylaldehydes with methyl propiolate or propynenitrile in the presence of TiBr4 are very slow at room temperature (20°C). The corresponding α-brominated compounds, derived from the reactions of arylaldehydes with methyl propiolate, were obtained in low yields. While, at 70°C in 1,2-dichloroethane, β,β-dibrominated compounds were obtained from the reactions of arylaldehydes with methyl propiolate or propynenitrile in the presence of TiBr4 in moderate yields. The substituent on the phenyl ring can affect the reaction rate and the E/Z ratio. In addition, with two substrate, palladium catalyzed allylic substitution and Suzuki-type coupling reaction have been examined. [Copyright &y& Elsevier]