Polymorphic Study of 2-(2-benzofuryl) Δ-2 Imidazoline

The compound 2-(2-benzofuryl) Δ-2 imidazoline, has been studied by DSC, TG, X-ray diffraction and thermomicroscopy. We shall see that in the case of a study by DSC this compound presents a strange behaviour, which apparently is in contradiction with the thermodynamic rules. In a case of monotropy, if we have the α-phase (stable) and the γ-phase (metastable), after melting and cooling only theα-phase could crystallise. But this compound can give, according to the rate of cooling, theγ-phase metastable. The rate of cooling is of fundamental importance and the monotropic behaviour of this compound will be explained using the Gibbs function G=f(T) for P=1 atm. This revised version was published online in August 2006 with corrections to the Cover Date.     

Conversions of 2-α-chloroalkylbenzimidazoles

Upon interaction with caustic in a DMSO medium, 2-chloromethylbenzimidazoles are subjected to cyclodimerization, forming 5H,12H-pyrazino[1,2-a:4,5-a]bis-benzimidazoles; in the presence of nucleophiles (ammonia, amines, anions of -diketones), under the indicated conditions, the products are the corresponding substituted amines or derivatives of pyrrolo[1,2a]benzimidazole.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 664–672, May, 1993.     

Photoprotection of wool with sulfonated 2-(2′-hydroxyaryl)-2H-benzotriazoles

A range of phenolic benzotriazolesulfonic acids containing a wide variety of substituents has been synthesized. These compounds protect wool to a significant extent against photo-tendering and, in some cases, against photo-yellowing. The protective effect is dependent on the nature and position of the substituents and is enhanced by (1) locating the sulfonic acid group distant from the hydrogen-bonded phenolic group and (2) placing bulky alkyl groups ortho to this phenolic group. The protective effect of one of the best photostabilizers (II) has been studied in detail and has been found to depend on both the concentration of the photostabilizer and the pH at which it is applied. The photostabilizer (II) also protects dyed wool to some extent against photo-fading as well as against phototendering.     

Crystal Structure of 2-(4-Fluorophenylamino)-2-thiomethyl acetophenone

1mThODUCTIONThioacetalshavebeenwellstudied,becauseoftheirapplicationsinorganicsyn-thesist1i.However,aketohemithioacetalshaveseldombeeninvestigated.Inthispa-Per,wediscussedthecrystalstructureofthetitlecompoundsynthesizedbythereac-tionofabenzoylhemithioacetal(2-hydroxy-2-thiomethylacetoPhenone)and4-fluthroaniline.Sinceknowledgeofthemolecularandcrystalstructureofthetitlecom-PoundwasconsideredusefulforunderstandingthemechanismofthereactionandchemicalproPertiesofaketohemithioacetal,theX-raycr…     

Solubility of Oxygen in Some 1-1, 2-1, 1-2, and 2-2 Electrolytes as a Function of Concentration at 25°C

The solubility of oxygen has been measured in a number of electrolytes [(LiCl, KCl, RbCl, CsCl, NaF, NaBr, NaI, NaNO₃, KBr, KI, KNO₃, CaCl₂, SrCl₂, BaCl₂, Li₂SO₄, K₂SO₄, Mn(NO₃)₃)] as a function of concentration at 25°C. The solubilities, mol (kg-H₂O)^–1, have been fitted to a function of the molality m (standard deviation < 3mol-kg^–1)

Multiwavelength spectrophotometric determination of acidity constants of 1-（2-thiazolylazo）-2-naphthol in methanol-water mixtures

The acid-base properties of 1-(2-thiazolylazo)-2-naphthol (TAN) in mixtures of methanol-water at 25℃and an ionic strength of 0.1 mol/L are studied by a multi-wavelength spectrophotometric method.The acidity constants of all related equilibria are estimated using the whole spectral fitting of the collected data to an established factor analysis model DATAN program was used for determination of acidity constants.The corresponding pK_a values in methanol-water mixtures were determined.There is a linear relationship between acidity constants and the mole fraction of methanol in the solvent mixtures.     

Modular synthesis of 1-α- and 1-β-(indol-2-yl)-2'-deoxyribose C-nucleosides

A simple two-step method for the selective preparation of anomerically pure 1α- and 1β-(indol-2-yl)deoxyribose derivatives was developed. The synthesis was based on the Sonogashira reaction of 1α- and 1β-ethynyldeoxyribose and 2-haloanilines followed by a Pd-complex catalyzed cyclization to the corresponding indolyldeoxyribosides.     

Synthesis of the 3-0, 4-0 and 6-0 Sulfates of Methyl 2-amino-2-deoxy-α-D-Glucopyranoside

Abstract

Starting with methyl 2-(benzyloxycarbonyl)amino-2-deoxy-α-D-glucopyranoside (1), the isomeric methyl 2-amino-2-deoxy-α-D-glucopyranoside 3-, 4-, and 6-sulfates have each been prepared by sulfation of suitably blocked intermediates. Tritylation and acetylation of 1 followed by detritylation gave methyl 3,4-di-0-acetyl-2-(benzyloxycarbonyl)amino-2-deoxy-α-D-glucopyranoside (3), having a free 6-hydroxyl group. Base catalyzed 0–4→0–6 acetyl migration provided the corresponding 3,6 di-O-acetyl derivative (4) posessing a free 4-hydroxyl group. Preparation of methyl 4,6-0-benzylidene-2-(benzyloxycarbonyl)amino-2-deoxy-α-D-glucopyranoside (9) provided the intermediate bearing a free 3-hydroxyl group. 0-sulfation of 3, 4, and 9 was effected with the pyridine sulfur trioxide complex in dry pyridine.     

Synthesis and Crystal Structure of 3-（2-Hydroxy-phenyl）-5-（2-methylphenyl）-6-thoxycarbonyl-cyclohexen-2-one

1 INTRODUCTION The molecular assembly of one- or multi-dimen-sional aggregation by hydrogen bonds is now an im-portant subject of supramolecular chemistry and crys-tal engineering[1, . Supramolecular structures formed 2]via intermolecular hydrogen bonds X–H…X or C–H…X (X = O, Cl, N, et al.) are very common inorganic compounds[3~12], and they generally possessdifferent properties due to these hydrogen bonds. Concerning about the spectra of benzene-contai-ning…     

Synthesis of 2-(2-Thienyl)benzimidazoles by the Reaction of 2-(Mercaptomethyl)benzimidazole With β-Electrophilic Esters

New 2-(2-di- and tetrahydrothienyl)benzimidazole compounds were prepared by the ring closure reactions of 2-(mercaptomethyl)benzimidazole^1,2 (1) and α,β-unsaturated compounds activated with electron-withdrawing groups.     

Synthesis and properties of 3-amino-2-(2-benzimidazolyl)-Δ2-pyrrolizidin-1-one

2-Benzimidazolylacetonitrile is acetylated by the acid chloride derivative of N-trifluoroacetylproline to give N- and C-acyl derivatives. Removal of the trifluoroacetyl protective group in the C-acyl derivatives is accompanied by cyclization to give 3-amino-2-(2-benzimidazolyl)-²-pyrrolizidin-1-one. Exhaustive acylation of this product gives a derivative of a new heterocyclic system, namely, pyrrolizino[3',2':5,6]-pyrimido[3,4-a] benzimidazole.Taras Shevchenko Kiev University, 252601 Kiev, Ukraine. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 975–978, July, 1997.     

Liquid-Phase Synthesis of Methyl (2Z)-2-Arylsulfonylmethyl-2- alkenoates from PEG-Supported α-Phenylselenopropionate

Treatment of lithio derivative of novel PEG-supported a-phenylselenopropionate with aldehydes, followed by oxidation-elimination with 30% hydrogen peroxide, formed Baylis-Hillman products, which were then reacted with sodium arylsulfinate. The resulting sulfonylated products were cleaved from the PEG efficiently affording methyl (2Z)-2-arylsulfonylmethyl-2-alkenoates in good yields and high purities.     

Synthesis and properties of 5-furyl(aryl)-Δ2-1,2,4-triazolines and -Δ2-1,3,4-thiadiazolines. Molecular and crystal structure of 2-acetylamino-5-phenyl-Δ2-1,3,4-thiadiazoline

We show that upon acylation of arylidene amidrazones of 5-nitro-2-furancarboxylic acid, 3-(5-nitro-2-furyl)-²-1,2,4-triazolines or 5-(5-nitro-2-furyl)-1,2,4-triazole are formed (depending on the structure of the arylidene moiety). ²-1,3,4-thiadiazolines are obtained by reaction of thiosemicarbazones of aromatic and furaldehydes and furan ketones. We discuss schemes for closure of the triazolidine, triazole, and thiadiazoline rings. We describe the molecular structure of 2-acetylamino-4-acetyl-5-phenyl-²-1,3,4-thiadiazoline.Kuban State Technological University, Krasnodar 350072. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1337–1344, October, 1994. Original article submitted October 11, 1994.     

Scope and limitations of the photooxidations of 2-(α-hydroxyalkyl)furans: synthesis of 2-hydroxy-exo-brevicomin

Photooxygenation of 2-(α-hydroxyalkyl)furans at 5 °C in MeOH followed by in situ reduction affords, in one synthetic operation, 6-hydroxy-3(2H)-pyranones and/or 5-hydroxy-2(5H)-furanones. The relative ratio of the final products is highly dependent on the substitution of the starting furan substrate. Photooxygenation of 2-(α,β-dihydroxyalkyl)furans followed by in situ reduction and ketalization with acid rapidly provides the 6,8-dioxabicyclo[3.2.1]oct-3-en-2-one framework. This new methodology was successfully applied to the synthesis of 2-hydroxy-exo-brevicomin.     

Synthesis of 5-[5-(α-Naphthyl)-2H-Tetrazol-2-Methylene]-2-Aroylamino-1, 3,4-Thiadiazoles

Introduction Acylthiosemicarbazides have been reported to possess extensive physiological activities. Substituted thiadiazoles are known to exhibit fungicidal and insecticidal activities. Chen Limin and her coworkers reported that the cyclization of 1[5-(3'-pyridyl )-2H-tetrazol-2-acetyl-]-4-acylthiosemicarbazides gave 5-[5-(3'-     

Synthesis of Dimedone-Annelated Heterocycles: Regioselective Heterocyclization of 2-(Cyclohex-2′-enyl)-5,5-dimethyl-3-hydroxy cyclohex-2-enone

Abstract

2-(Cyclohex-2′-enyl)-5,5-dimethyl-3-hydroxycyclohex-2-enone undergoes regioselective heterocyclization to give bridged heterocycles 5a,b and 7 on treatment with pyridine hydrotribromide or hexamethylenetetramine hydrotribromide (1 h); or elemental bromine (7 h); N-iodosuccinimide in acetonitrile at 0–5°C (1 h) and conc. H₂SO₄ at 0–5°C (2 h), respectively.     

Enantioselective synthesis of 2-substituted-N-Boc-Δ-4,5-piperidines

The title compounds were prepared through a synthetic sequence involving: (i) a reaction of the condensation product between an enantiopure β-amino alcohol and an aldehyde with allylmagnesium chloride; (ii) an N-allylation of the resulting secondary amine; (iii) a chemoselective cleavage of the β-amino alcohol residue; and (iv) a protection of the secondary amine followed by a ring closing metathesis. The advantageous use of (1R,2S)-norephedrine was demonstrated in these syntheses.     

Synthesis of metal complexes with 2-[bis(2-phenylethyl)-thiophophorylhydroxymethyl]-1-organilimidazoles. Crystal structure of ZnCl2 · 2L

The reactions of Zn(II), Cd(II), Cu(II), Co(II), Pd(II) dichlorides with 2-[bis(2-phenylethyl)thiophosphorylhydroxymethyl]-1-organilimidazoles (L¹–L⁴) were studied. The novel complexes were synthesized and characterized by IR and NMR spectroscopies. Depending on the nature of imidazolephosphinesulfide, both monodentate (at the “pyridine” N(1) atom of heterocycle) and the N,S-bidentate binding of the ligand by a metal can be realized in the above metal complexes. The structure of the complex ZnCl₂ · 2L⁴(I) (L⁴ = 2-[bis(2-phenylethyl)thiophosphorylhydroxymethyl]-1-ethylbenzimidazole) was studied by X-ray diffraction. One of the two independent L⁴ molecules performs the solvate function, while another one, together with two Cl atoms, is coordinated through the atoms N(1) and S to the Zn atom at the vertices of a slightly distorted tetrahedron. The molecule of the complex is united with the solvate molecule into [ZnCl₂L₄]L⁴ associates by strong intermolecular hydrogen bonds to give nonplanar four-membered H-cycle OH₂N.     

Electrochemical transformations of 2-̀hydroxychalcones into flavanoids

2′-Hydroxychalcones are cyclized to flavanones, and flavone, or flavonol, by electrochemically generated tris-(4-bromophenyl)amine cation radical as homogeneous electron-transfer agent.