Synthesis of photoactive bichromophoric dyads containing 2-styrylquinoline and 2-naphthol moieties

A three-step approach to the synthesis of bichromophoric dyads of the general formula SQ-(CH₂) _n -Np (SQ is the 2-(4-oxystyryl)quinoline moiety, Np is the 3-oxy-2-naphthol moiety, n = 2, 4, 5) was developed from available reagents.     

An Efficient Synthesis of New 3,4-Dihydropyrimidin- 2(1H)-ones Incorporating a Phenyl Moiety at C-5 and C-6 Catalyzed by TMSCl and Co(OAc)2.4H2O

New 3,4-dihydropyrimidin-2-ones having a phenyl moiety at C-5 and C-6 have been prepared by a microwave-assisted Biginelli–like reaction by a three-component, one-pot condensation of an aromatic aldehyde, deoxybenzoin and urea, or thiourea using TMSCl and Co(OAc) ₂ .4H ₂ O as an efficient Lewis acid catalyst.     

Reaction of Substituted 2-Allylthiopyrimidin-4(3H)-ones with Sulfenyl Chlorides

Reaction of substituted 2-allylthiopyrimidin-4(3H)-ones with p-nitrobenzosulfenyl chloride gives the products of addition at the allyl moiety, while the reaction with 2-benzothiazolyl sulfenyl chloride yields thiazolidinopyrimidines with an angular structure.     

NMR study of 4-deoxy-α-L-threo-4-enohexopyranosyluronic acid (1 → 3)2-acetamido-2-deoxy-D-hexoses produced in the enzymic digestion of hyaluronate,chondroitin and chondroitin sulfates

The conformation of 4-deoxy-α-L -threo-4-enohexopyranosyluronic acid (1 → 3)2-acetamido-2-deoxy-d-hexoses was analyzed by NMR spectroscopy. The half-chair (H₁²) conformation was found in the unsaturated uronide moiety and the chair (Cl) conformation in the hexosamine moiety.     

Reagents for new heteroannelation reactions III. 2-(Methylthio)-2-thiazoline

Summary A variety of partly novel tri- and tetracyclic hetero systems were obtained by reaction of heteroaromatic 2-aminoesters with 2-(methylthio)-2-thiazoline, yielding double-annelation of a thiazolo[2,3-b]pyrimido moiety in a one-pot process.On leave from University of Chittagong, Bangladesh     

One‐Pot Syntheses of 2‐(2‐Sulfanyl‐4H‐3,1‐benzothiazin‐4‐yl)acetic Acid Derivatives via Reactions of 3‐(2‐Isothiocyanatophenyl)prop‐2‐enoic Acid Derivatives with Thiols or Sodium Sulfide

Two efficient methods for the preparation of 2‐(2‐sulfanyl‐4H‐3,1‐benzothiazin‐4‐yl)acetic acid derivatives 3 under mild conditions have been developed. The first method is based on the reaction of 3‐(2‐isothiocyanatophenyl)prop‐2‐enoates 1a – 1c with thiols in the presence of Et₃N in THF at room temperature, leading to the corresponding dithiocarbamate intermediates 2 , which underwent spontaneous cyclization at the same temperature by an attack of the S‐atom at the prop‐2‐enoyl moiety in a 1,4‐addition manner (Michael addition) to give 2‐(2‐sulfanyl‐4H‐3,1‐benzothiazin‐4‐yl)acetates in one pot. The second method involves treatment of 3‐(2‐isothiocyanatophenyl)prop‐2‐enoic acid derivatives 1b – 1d with Na₂S leading to the formation of 2‐(2‐sodiosulfanyl‐4H‐3,1‐benzothiazin‐4‐yl)acetic acid intermediates 5 by a similar addition/cyclization sequence, which are then allowed to react with alkyl or aryl halides to afford derivatives 3 . 2‐(2‐Thioxo‐4H‐3,1‐benzothiazin‐4‐yl)acetic acid derivatives 6 can be obtained by omitting the addition of halides.     

Discovery of 4,6-bis(2-((E)-benzylidene)hydrazinyl)pyrimidin-2-Amine with Antibiotic Activity

Robenidine (E)-N′-((E)-1-(4-chlorophenyl)ethylidene)-2-(1-(4-chlorophenyl)ethylidene)hydrazine-1-carboximidhydrazide displays methicillin-resistant Staphyoccoccus aureus (MRSA) and vancomycin-resistant Enterococci (VRE) MICs of 2 μg mL⁻¹. Herein we describe the structure-activity relationship development of a novel series of guanidine to 2-aminopyrimidine isosteres that ameliorate the low levels of mammalian cytotoxicity in the lead compound while retaining good antibiotic activity. Removal of the 2-NH₂ pyrimidine moiety renders these analogues inactive. Introduction of a central 2-NH₂ triazine moiety saw a 10-fold activity reduction. Phenyl to cyclohexyl isosteres were inactive. The 4-BrPh and 4-CH₃Ph with MIC values of 2 and 4 μg mL⁻¹, against MRSA and VRE respectively, are promising candidates for future development.     

Selective Transformations of a Diprotected 2‐Oxobutanedial

The reactivity of 1,1‐diethoxy‐3‐(1,3‐dithian‐2‐yl)propan‐2‐one, a diacetal of oxobutanedial, and some of its derivatives toward selected reagents has been studied. As expected, hydride and Grignard‐type additions take place at the oxo moiety only and give the corresponding alcohols in good‐to‐excellent yields. Standard reductive amination occurs at the oxo moiety as well, but the reaction was in most cases not selective and furnished the expected amine mixed with 3‐(1,3‐dithian‐2‐yl)‐1,1‐diethoxypropan‐2‐ol. The conversion of the diethyl acetal moiety to an aldehyde group is generally an efficient transformation, but some aldehydes are unstable, making the deprotection useless. If the acetal contains a tertiary alcohol or a benzyloxy moiety, however, stable products are formed in good yields. Attempts to convert the 1,3‐dithiane substituent into an aldehyde group without concomitant decomposition of the product were totally unsuccessful. The chemical potential of this moiety, therefore, has to be utilized at an earlier stage and under different conditions.     

Simulation of optical response to complex formation of crown-containing 2-styrylbenzothiazoles with alkaline-earth metals

The photochromic properties and complex formation of 2-styrylbenzothiazoles containing different crown ether moieties with alkaline-earth metals were described using optical methods, NMR spectroscopy, and HPLC. The large ionochromic effect and fluorescence quenching on complex formation with alkali-earth metal cations were found for 2-styrylbenzothiazole containing the phenylazacrown ether moiety. The small ionochromic effect and fluorescence enhancement of complex formation with alkali-earth metal cations were found for 2-styrylbenzothiazole containing the benzocrown ether moiety. cis-Isomers of 2-styrylbenzothiazoles were stable in the dark in acetonitrile. The method for separation of cis-isomers of 2-styrylbenzothiazoles by HPLC was proposed.     

Monodentate imido coordination of 2-aminodiphenylamine to rhenium(V)

The complex trans-[Re(ada)Cl₃(PPh₃)₂] (H₂ada?=?2-aminodiphenylamine) was prepared from the reaction of trans-[ReOCl₃(PPh₃)₂] with H₂ada in acetonitrile. The ligand ada is coordinated to the rhenium(V) centre solely through a dianionic imido nitrogen, with distorted octahedral coordination geometry around the metal ion. Surprisingly, the Re–Cl bond trans to the Re=N bond is shorter than the two equatorial Re–Cl bonds. The Re?=?N–C bond angle of the phenylimido moiety equals 178.7(4)°.     

Facile synthesis of 1-(arylimino)naphthalen-2(1H)-ones from anilines and 2-naphthols promoted by NaBr/K2S2O8/CAN

An efficient method has been developed for the synthesis of 1-(arylimino)naphthalen-2(1H)-ones through the cascade reaction of anilines and 2-naphthols promoted by NaBr/K₂S₂O₈/Ce(NH₄)₂(NO₃)₆. Using this protocol, a series of 1-(arylimino)naphthalen-2(1H)-ones was obtained in good to excellent yields (17 examples, 70–92% yields). The reactions may proceed through the following steps: bromination of 2-naphthols by in-situ-generated bromine from NaBr and K₂S₂O₈ to afford 1-bromonaphthalen-2-ols, coupling of 1-bromonaphthalen-2-ols with anilines to afford the corresponding amines, and subsequent oxidation of the amines into the products by Ce(NH₄)₂(NO₃)_6. These newly obtained α-imine ketones have great potentials for synthesis of special optical materials bearing naphthalene moiety.     

Synthesis of (2′S)‐2′‐Deoxy‐2′‐C‐methylpurine Nucleosides and Their Phosphoramidites

We describe the stereoselective synthesis of (2′S)‐2′‐deoxy‐2′‐C‐methyladenosine ( 12 ) and (2′S)‐2′‐deoxy‐2′‐C‐methylinosine ( 14 ) as well as their corresponding cyanoethyl phosphoramidites 16 and 19 from 6‐O‐(2,6‐dichlorophenyl)inosine as starting material. The methyl group at the 2′‐position was introduced via a Wittig reaction (→ 3 , Scheme 1) followed by a stereoselective oxidation with OsO₄ (→ 4 , Scheme 2). The primary‐alcohol moiety of 4 was tosylated (→ 5 ) and regioselectively reduced with NaBH₄ (→ 6 ). Subsequent reduction of the 2′‐alcohol moiety with Bu₃SnH yielded stereoselectively the corresponding (2′S)‐2′‐deoxy‐2′‐C‐methylnucleoside (→ 8a ).     

A New Chair‐shaped Conformation Containing HgHgOHgHgO: Synthesis and Structure of Hg4(L2)2(NO3)4 (L2 = morpholin‐4‐ylpyridin‐2‐ylmethyleneamine)

. The complex Hg₄(L²)₂(NO₃)₄ ( 1 ) (L² = morpholin‐4‐ylpyridin‐2‐ylmethyleneamine) has been synthesized and characterized by CHN analysis, IR, and UV/Vis spectroscopy. The crystal structure of 1 was determined using single‐crystal X‐ray diffraction. The crystal structure of 1 contains four mercury atoms, four nitrate anions (two terminal and two bridge ones) and two L² ligand molecules. A chair shape, six‐membered ring is formed with the sequence OHgHgOHgHg built from Hg–Hg dumbbells and oxygen atoms from the nitrate co‐ligands. In the crystal structure, the asymmetric unit of the compound is built up by one‐half of the molecule. It contains the Hg₂²⁺ moiety with a mercury–mercury bonded core, in which one diimine ligand is coordinated to one of the mercury atoms. The nitrate anions act as anisobidentate and bidentate ligands.     

Dinuclear Zinc Catalyzed Enantioselective Dearomatization [3+2] Annulation of 2-Nitrobenzofurans and 2-Nitrobenzothiophenes

The application of dinuclear zinc catalysts in a dearomatization reaction has been developed. Catalytic asymmetric dearomatization [3+2] annulations of 2-nitrobenzofurans or 2-nitrobenzothiophenes with CF₃-containing N-unprotected isatin-derived azomethine ylides catalyzed by dinuclear zinc catalysts are realized with excellent diastereomer ratios (dr) of >20 : 1 and enantiomeric excess (ee) of up to 99 %. This protocol provides a practical, straightforward access to structurally diverse pyrrolidinyl spirooxindoles containing a 2,3-fused-dihydrobenzofuran (or dihydrobenzothiphene) moiety, and four contiguous stereocenters. Reactions can be performed on a gram scale. The absolute configuration of products is confirmed by X-ray single crystal structure analysis, and a possible mechanism is proposed.     

2‐Amino‐8‐(2‐deoxy‐2‐fluoro‐β‐d‐arabinofuranosyl)imidazo[1,2‐a][1,3,5]triazin‐4(8H)‐one monohydrate,a 2′‐deoxyguanosine analogue with an altered Watson–Crick recognition site

The title compound, C₁₀H₁₂FN₅O₄·H₂O, shows an anti glycosyl orientation [χ = −123.1 (2)°]. The 2‐deoxy‐2‐fluoroarabinofuranosyl moiety exhibits a major C2′‐endo sugar puckering (S‐type, C2′‐endo–C1′‐exo, ²T₁), with P = 156.9 (2)° and τ_m = 36.8 (1)°, while in solution a predominantly N conformation of the sugar moiety is observed. The conformation around the exocyclic C4′—C5′ bond is −sc (trans, gauche), with γ = −78.3 (2)°. Both nucleoside and solvent molecules participate in the formation of a three‐dimensional hydrogen‐bonding pattern via intermolecular N—H...O and O—H...O hydrogen bonds; the N atoms of the heterocyclic moiety and the F substituent do not take part in hydrogen bonding.     

Synthesis of Oximes with NH2OH.HCl/DOWEX(R)50WX4 System

The oximation of a variety of carbonyl compounds was efficiently carried out with DOWEX(R)50WX4/NH₂OH·HCl system. The reactions were performed in ethanol to give Z‐aldoximation isomers of aldehydes and E‐oximaton of acetophenone derivatives in a perfect selectively. The oximation of compounds with two carbonyl groups was carried out selectively on one carbonyl moiety. Also, the oximation of aldehydes over ketones has been accomplished successfully by this system.     

Metalla-Claisen Rearrangement in Gold-Catalyzed [4+2] Reaction: A New Elementary Reaction Suggested for Future Reaction Design

We report here computational evidence for a metalla-Claisen rearrangement (MCR) in the case of gold-catalyzed [4+2] cycloaddition reaction of yne-dienes. The [4+2] reaction starts from exo cyclopropanation, followed by MCR and reductive elimination. The cyclopropane moiety formed in the first step is crucial for a low barrier of the MCR step. In addition, the importance of an appropriate combination of the tether group and the terminal substituent on alkyne in the yne-diene substrates was studied. The mechanism of rhodium-catalyzed [4+2] reaction of yne-dienes was also investigated to see whether an MCR mechanism is involved or not. The findings and new understanding hereby reported represent an important advance in the catalysis field.     

Reaction of 5-aryl-2-tosylmethylimino-2,3-dihydro-3-furanones with substitutedN-(benzylidene)benzylamines. Crystal structure of 1-benzyl-5-p-methoxyphenyl-2-(p-chlorobenzoyl)acetylimidazole

5-Aryl-2-aroylacetyl-1-benzylimidazoles were synthesized by treatment of 5-aryl-2-tosylmethylimino-2, 3-dihydro-3-furanones withN-(benzylidene)benzylamines containing electron-donating substitutents in the benzylidene moiety. The structure of 1-benzyl-5-p)-methoxyphenyl-2-(p-chlorobenzoyl)acetylimidazole was studied by X-ray diffraction.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2013–2016, October, 1995.     

Röntgenstrukturanalyse von N-((E)-2-Methyl-2-butenyl)-N-(4-methylphenylsulfonyl)-N′-(4-nitrophenyl)schwefeldiamid

X-Ray Structure Analysis of N-((E)-2-Methyl-2-butenyl)-N-(4-methylphenylsulfonyl)-N′-(4-nitrophenyl)sulfurdiamide The title compound crystallizes in the monoclinic space group P2₁/n with a = 16.893(3), b = 14.285(2), c = 18.422(4), β = 114.765(5)°, V = 4037 ų, Z = 8. The formal S? N single bonds of the diaminosulfane moiety are shortened and differ in length (1.700 and 1.644 Å). The bonds of the N? S? N group to the p-nitrophenyl and tosyl rest are also a bit shorter than single bonds. The hybridization of the N atoms of the N? S? N moiety is sp² with a tendency in the direction of sp³. Analogously to open chained sulfur diimides with respect to the N? S? N moiety an E/Z configuration can be derived. In the crystal structure the molecules are connected to one-dimensional polymers via hydrogen bridges between the nitrogen of the secondary amino group as a donor and an oxygen of the nitro group as an acceptor.     

Living Anionic Polymerization of N-Methacryloyl-2-methylaziridine

Anionic polymerization of N-methacryloyl-2-methylaziridine ( 1 ) proceeded with 1,1-diphenyl-3-methylpentyllithium (DMPLi) in the presence of LiCl or Et₂Zn to give the polymers possessing predicted molecular weights and narrow molecular weight distributions (M_w/M_n < 1.1) at −78 ∼ −40 °C in THF. In each polymerization initiated with DMPLi/LiCl at the various temperatures ranging from −40 to −60 °C, the linear relationship between polymerization time and conversion of monomer was obtained from the GLC analysis. The rate constant and the activation energy of the anionic polymerization for 1 were determined as follows: ln k = −5.85 × 10³/T + 23.3 L mol⁻¹ s⁻¹ and 49 ± 4 kJ mol⁻¹, respectively. Poly( 1 ) showed the glass transition temperature at 98 °C, and gave the insoluble product at higher temperature around 150 °C through the thermal cross-linking of highly strained N-acyl-aziridine moiety.