Syntheses of substituted 1-methyl-2-(1,3,4-thiadiazol-2-yl)-4-nitropyrroles and 1-methyl-2-(1,3,4-oxadiazol-2-yl)-4-nitropyrroles

Starting from readily available ethyl-4-nitropyrrole-2-carboxylate ( 1 ), substituted 1-methyl-2-(1,3,4-thiadiazol-2-yl)-4-nitropyrroles and 1-methyl-2-(1,3,4-oxadiazol-2-yl)-4-nitropyrroles were prepared. The reaction of 1 with diazomethane gave ethyl 1-methyl-4-nitropyrrole-2-carboxylate ( 2 ). Reaction of compound 2 with hydrazine hydrate afforded the corresponding hydrazide 3 . The reaction of 3 with formic acid yielded 1-(1-methyl-4-nitropyrrole-2-carboxyl)-2-(formyl)hydrazine ( 7 ). Refluxing of the latter with phosphorus pentasulfide in xylene yielded compound 6 in 40% yield. Reaction of compound 7 with phosphorus pentoxide afforded compound 9 . Reaction of compound 3 with 1,1′-carboxyldiimidazole in the presence of triethylamine yielded 2-(1-methyl-4-nitro-2-pyrrolyl)-1,3,4-oxadiazoline-4(H)-5-one ( 11 ). Refluxing compound 3 with cyanogen bromide in methanol gave compound 12 . Compound 13 could be obtained through the reaction of compound 3 with carbon disulfide in basic medium. Alkylation of compound 13 afforded the correspanding alkylthio derivative 14 . Reaction of 1-methyl-4-nitropyrrole-2-carboxylic acid ( 15 ) with thiosemicarbazide and phosphorus oxychloride gave 2-amino-5-(1-methyl-4-nitro-2-pyrrolyl)-1,3,4-thiadiazole ( 16 ). Sandmeyer reaction of compound 16 yielded 2-chloro-5-(1-methyl-4-nitro-2-pyrrolyl)-1,3,4-thiadiazole ( 17 ). Refluxing of the latter with thiourea afforded 2-(1-methyl-4-nitro-2-pyrrolyl)-1,3,4-thiadiazoline-4(H)-5-thione ( 18 ). Alkylation of compound 18 gave the corresponding alkylthio derivative 19 . Oxidation of the latter with hydrogen peroxide in acetic acid yielded 2-(1-methyl-4-nitro-2-pyrrolyl)-5-methylsulfonyl-1,3,4-thiadiazole ( 20 ).     

Preparation of twelve 1-methyl-2-formyl-5-substituted pyrroles and their hydrazones

Preparation of twelve 1-methyl-2-formyl-5-substituted pyrroles (2a-1), with five of them as new compounds, is described. Their derivatives, i.e., 1-methyl-2-formyl-5-substituted pyrrole phenyl hydrazones (3a-1) and 1-methyl-2-formyl-5-substituted pyrrole (4-nitrophenyl) hydrazones (4a-1) are all new compounds. They have also been prepared and further identified.     

Benzindoles. 23. 2-formyl- and 3-formyl-4,5-benzindoles

It is shown that, in addition to the usually formed 3-formyl-4,5-benzindole, 2-formyl-4,5-benzindole can be obtained via the Vilsmeier reaction. The IR, PMR, and UV spectra of the 2- and 3-formyl isomers are compared, and their possible conformations are discussed.See [1] for Communication 22.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 343–345, March, 1984.     

Polyfunctional Pyrazoles. 2. 1-Aryl-3-benzoyl-4-formyl- and 4-Carboxypyrazoles

Cyclization of 1-phenylpropane-1,2-dione monoarylhydrazones under Vilsmeier-Haack conditions gave 1-aryl-3-benzoyl-4-formylpyrazoles which were converted to 1-aryl-3-benzoyl-4-carboxypyrazoles using potassium permanganate in aqueous pyridine medium.     

Synthesis and properties of 3-formyl-4H-pyrans

The Vilsmeier formylation of 4H-pyrans afforded 3-formyl-4H-pyrans. These were converted to 3-formylpyrylium salts, from which pyridine or pyridine salts with an aldehyde group at C₍₃₎ were obtained. The reaction between 3-formyl-4-allyl-4H-pyran and methyltrifluoromethanesulfonate proceeded via a Koop rearrangement.Translated from Khimiya Geterotsiklicheskii Soedinenii, No. 5, pp. 603–607, May, 1990.     

Cyclizaticn of 3-formyl-2-acetylenylindole oximes

Conclusions 3-Formyl-2-acetylenyl-1-methylindole oximes readily undergo intramolecular heterocyclization with closure of a pyridine ring and formation of substituted-carboline N-oxides.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 11, pp. 2602–2604, November, 1984.     

Disulfide derivatives of thiosemicarbazones of 4-formyl-5-thiopyrazole

The reaction of 4-formyl-5-mercaptopyrazole with thiosemicarbazides in methanol has afforded novel disulfide derivatives of thiosemicarbazones, and their structure has been studied by NMR and IR spectroscopy. X-ray diffraction analysis of [5,5'-dithiobis(4-formyl-3-methyl-1-phenylpyrazole)]-4-allylthio-semicarbazone has shown that it exists as a dimer with two molecules linked via the disulfide S–S bridge between the heterocycles in the crystal.     

Synthesis and structure of anils of 2-formyl-3-mercaptobenzo[b]thiophene and 2-formyl-3-mercaptobenzofuran

As a result of a study of the electronic, vibrational, and PMR spectra of alkyl- and arylimines of 2-formyl-3-mercaptobenzo[b]thiophene and 2-formyl-3-mercaptobenzofuran and of the spectra of model compounds the thione-enamine structure was assigned to the imines. The stability of the latter structure is in agreement with the results of quantum-mechanical calculations of the energies of atomization of the individual tautomeric forms; the calculations were made by means of the Pariser-Parr-Pople (PPP) method with the Dewar σ, π parametrization.     

Base-promoted isomerization of cis-4-formyl-2-azetidinones: chemoselective C4-epimerization vs rearrangement to cyclic enaminones

Two simple, efficient, and complementary methods for the regiospecific C4-epimerization of cis-4-formyl-2-azetidinones 1-3 are described. The first method uses 40% aqueous dimethylamine as reagent in heterogeneous medium with benzene at room temperature, in the presence of benzyltributylammonium bromide (3-4 mol%) as the phase-transfer catalyst. This transformation tolerates alkyl, alkenyl, alkynyl, aryl, and alkoxy substituents at the C3 of the 2-azetidinone ring. However, limitations of this isomerization are as follows: (i) only N-(p-methoxyphenyl)-beta-lactams can be used, and (ii) transformation is less compatible with heteroatomic substituents bonded to the C3 position of the 2-azetidinone ring. A highly general solution to these problems relies on the use of sodium carbonate as the isomerization reagent in different solvents. We also describe a novel base-promoted rearrangement of the beta-lactam ring to cyclic enaminones 6 and 21, involving an E1cB-elimination reaction in cis-4-formyl-2-azetidinones.     

Copper(II) complexes of 2-formyl-, 6-methyl-2-formyl- and 2-benzoylpyridine N(4)-(2-methylpyridinyl)-,N(4)-(2-ethylpyridinyl)-and N(4)-methyl(2-ethylpyridinyl)thiosemicarbazones

Summary The title complexes of general formula [Cu(HL)Cl₂] or [Cu(L)Cl] have been isolated and characterized by ¹H and ¹³C-n.m.r., i.r. and electronic spectra. The i.r., electronic and e.s.r. spectral data for the Cu^II complexes are compared with those of previously studied complexes. The antitumour and antiviral activities of the thiosemicarbazones and their complexes are discussed.     

A new formylation reagent : 4-formyl-2-methyl-1,3,4-thiadiazolin-5-thione.

4-Formyl-2-methyl-1,3,4-thiadiazolin-5-thione, prepared from acetic formic anhydride, is found to act as a selective formylation reagent under mild conditions. The synthesis of some N-formyl antibiotics with this reagent is reported.     

Complexes of N(4)-cyclohexylsemicarbazones and N(4)-cyclohexylthiosemicarbazones derived from 2-formyl-, 2-acetyl- and 2-benzoylpyridine

2-Formyl-, 2-acetyl- and 2-benzoylpyridine N(4)-cyclohexylsemicarbazone and N(4)-cyclohexylthiosemicarbazone complexes of cobalt(II, III), nickel(II) and copper(II) have been prepared and characterized by molar conductivities, magnetic susceptibilities and spectroscopic techniques. For many of the complexes, coordination is by the neutral ligand, the main exceptions being the cobalt(III) complexes of the three thiosemicarbazones and three of the benzoylpyridine derivatives. Thus, bonding is via the pyridyl nitrogen, azomethine nitrogen and thione/thiolato sulfur. The five-coordinate copper(II) complex of 2-acetylpyridine N(4)-cyclohexylthiosemicarbazone, [Cu(HAc4CHex)Cl₂], approaches square pyramidal stereochemistry with the basal Cu—Cl bond significantly shorter than the apical Cu—Cl bond. This revised version was published online in June 2006 with corrections to the Cover Date.     

Reaction of 2-formyl-1,3-cyclohexanediones with cyanoacetamide

Chemistry of Heterocyclic Compounds -     

Thermodynamic Parameters of Some Schiff Bases Derived From 5,7-dihydroxy-6-formyl-2-methylbenzopyran-4-one

Potentiometric studies on Schiff bases derived from5,7-dihydroxy-6-formyl-2-methylbenzopyran- 4-one were carried out at different ionic strengths (0.02, 0.04, 0.06, 0.10 and 0.14 M NaCl), at different temperatures (25, 35, 45 and55°C) and in ethanol-water media of varying compositions (60, 70, 80 and 90% v/v). The ionization constants of the Schiff bases were investigated in the presence of different organic solvents (70% v/v), e.g. methanol, ethanol, n-propanol, isopropanol, acetone, DMSO and DMF-water media. The thermodynamic parameters (ΔG, ΔH and ΔS) were also calculated. This revised version was published online in July 2006 with corrections to the Cover Date.     

Electronic and vibrational spectra of chalcone analogs derived from 4- and 5-nitropyrroles

The electronic absorption spectra of ten chalcone analogs derived from 4- and 5-nitropyrroles have been measured in solution in ethanol, dioxane, concentrated sulfuric acid, and 20% ethanolic caustic potash and interpreted. The IR spectra of these compounds and also of 4- and 5-nitro-2-acetylpyrroles and 5-nitropyrrole-2-aldehyde have been measured in the 3700-500 cm^–1 region, an assignment of frequencies has been carried out, and considerations have been put forward on the connection between the characteristic features of the absorption and the chemical structure.