A novel 4.6 5-connected metal-organic framework with strong fluorescent emission constructed by m-thioacetatebenzoic acid

A novel uninodal 5-connected metal-organic framework (MOF), [Cd₂L₂(4,4′-bipy)_3/2(H₂O)₂]_n (H₂L=m-thioacetatebenzoic acid and 4,4′-bipy=4,4′-bipyridine), was prepared under hydrothermal condition. It features an unusual brick-wall shape layer by 4,4′-bipy, which consists of right- and left-handed helical chains arrayed alternatively and finally expands by L^2- to a rare 5-connected nov (4⁴.6⁶) topology network. Photoluminescence study reveals that it displays intense structure-related fluorescent emission bands (λ_ex=355 nm) at 450 nm in the solid state at room temperature.     

Silica-bonded S-sulfonic acid: an efficient and recyclable solid acid catalyst for the synthesis of 4,4′-(arylmethylene)bis(1H-pyrazol-5-ols)

Silica-bonded S-sulfonic acid (SBSSA) is employed as a recyclable catalyst for the condensation reaction of aromatic aldehydes with 3-methyl-l-phenyl-5-pyrazolone. This condensation reaction was performed in ethanol under refluxing conditions giving 4,4′-alkylmethylene-bis(3-methyl-5-pyrazolones) in 75-90% yields.     

Rapid synthesis of optically active poly(amide-imide)s by direct polycondensation of aromatic dicarboxylic acid with aromatic diamines

4,4^′-(Hexafluoroisopropylidene)-N,N^′-bis(phthaloyl-l-leucine-p-amidobenzoic acid) (2) was prepared from the reaction of 4,4^′-(hexafluoroisopropylidene)-N,N^′-bis(phthaloyl-l-leucine) diacid chloride with p-aminobenzoic acid. The direct polycondensation reaction of monomer (2) with p-phenylenediamine (2a), 4,4^′-diaminodiphenylsulfone (2b), 2,4-diaminotoluene (2c), 2,6-diaminopyridine (2d), m-phenylene diamine (2e), benzidine (2f), 4,4^′-diaminodiphenylether (2g) and 4,4^′-diaminodiphenyl methane (2h) was carried out in a medium consisting of triphenyl phosphite, N-methyl-2-pyrolidone, pyridine, and calcium chloride. The homogeneous mixture was heated at 220 °C for 1 min under nitrogen. The resulting poly(amide-imide)s (PAIs) having inherent viscosities 0.27-0.78 dl/g were obtained in high yield and are optically active and thermally stable. All of the above polymers were fully characterized by IR spectroscopy, elemental analyses and specific rotation. Some structural characterization and physical properties of this new optically active PAIs are reported.     

A new class of aromatic polybenzoxazoles containing ortho-phenylenedioxy groups

A series of poly(o-hydroxy amide)s having both ether and ortho-catenated phenylene unit in the main chain were synthesized via the low-temperature solution polycondensation of 4,4^′-(1,2-phenylenedioxy)dibenzoyl chloride and 4,4^′-(4-tert-butyl-1,2-phenylenedioxy)dibenzoyl chloride with three bis(o-aminophenol)s including 4,4^′-diamino-3,3^′-dihydroxybiphenyl, 3,3^′-diamino-4,4^′-dihydroxybiphenyl, and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane. The poly(o-hydroxy amide)s exhibited inherent viscosities in the range of 0.23-0.96 dl/g. Most of the poly(o-hydroxy amide)s were soluble in polar organic solvents such as N,N-dimethylacetamide (DMAc) and N-methyl-2-pyrrolidone (NMP) and could afford flexible and tough films by solution casting. Subsequent thermal cyclodehydration of the poly(o-hydroxy amide)s afforded polybenzoxazoles. However, the polybenzoxazoles were organic-insoluble except for those with the hexafluoroisopropylidene group. The polybenzoxazoles exhibited glass-transition temperatures (T_g) in the range of 200-232 °C by DSC and softening temperatures (T_s) of 250-256 °C by thermomechanical analysis. Thermogravimetric analyses indicated that most polybenzoxazoles were stable up to 500 °C in air or nitrogen. The 10% weight loss temperatures were recorded in the ranges of 546-606 °C in air and 574-631 °C in nitrogen.     

Synthesis and optical properties of a poly(2′,5′-dioctyloxy-4,4′,4″- terphenylenevinylene) with high content of (Z) vinylene units

Poly(2′,5′-dioctyloxy-4,4′,4″-terphenylenevinylene) with (E) configuration of the vinylene double bonds was prepared by Suzuki-Miyaura polymerization of (E)-4,4′-dibromostilbene and 2,5-dioctyloxy-1,4-benzenediboronic acid. Attempts to extend this simple procedure to the synthesis of the polymer with (Z) configuration, starting from (Z)-4,4′-dibromostilbene, were unsuccessful. However, the use of (Z)-4,4′-diiodostilbene and a careful choice of Pd catalyst and experimental conditions, lead to a material with a >95/<5 (Z)/(E) ratio of vinylene units. The investigation of optical properties of both the (E) and (Z) polymers evidenced that (Z) linkages act as defects which reduce the effective conjugation length in the polymer backbone.     

Cascade assembly of N,N′-dialkylbarbituric acids and aldehydes: a simple and efficient one-pot approach to the substituted 1,5-dihydro-2H,2′H-spiro(furo[2,3-d]pyrimidine-6,5′-pyrimidine)-2,2′,4,4′,6′(1′H,3H,3′H)-pentone framework

Cascade assembly of N,N′-dialkylbarbituric acids and aldehydes in the presence of bromine leads to the selective and efficient formation of substituted 1,5-dihydro-2H,2′H-spiro(furo[2,3-d]pyrimidine-6,5′-pyrimidine)-2,2′,4,4′,6′-(1′H,3H,3′H)-pentones in 70-88% yields via a complex cascade process. Spirobarbiturates containing the furo[2,3-d]pyrimidine framework are a class of compounds with interesting pharmacological and physiological activity.     

The remarkable configurational stability of ortho,ortho-tetrafluoro substituted biphenyls: 2,2,4,4,6,6-hexafluorobiphenyl-3,3-dicarboxylic acid as a model

Optically active 2,2^′,4,4^′,6,6^′-hexafluorobiphenyl-3,3^′-dicarboxylic acid was obtained through its brucine salt. The half-life time for racemization was determined at various temperatures and the torsional barrier for racemization was calculated to be 25.4 kcal/mol. These results prove, contrary to textbook knowledge, that ortho,ortho^′-tetrafluoro substituted biphenyls are resolvable.     

Synthesis of cyclic bis(3′-5′)diguanylic acid (c-di-GMP) analogs

This paper reports the synthesis of cyclic bis(3′-5′)diguanylic acid (c-di-GMP) analogs, including the monophosphorothioic acid of c-di-GMP (c-GpGps), cyclic bis(3′-5′)guanylic/adenylic acid (c-GpAp), and cyclic bis(3′-5′)guanylic/inosinic acid (c-GpIp). These compounds are expected to be important, both in elucidating the mechanism of bioactive c-di-GMP and in designing and creating new bioactive c-di-GMP-related artificial derivatives.     

Aqueous solution behavior of p(N-isopropyl acrylamide) in the presence of water-soluble macromolecular species

We report here the polymerization of N-isopropyl acrylamide (NIPAM) via the reversible addition fragmentation chain transfer (RAFT) process. Two trithiocarbonates (S,S′-bis(α,α′-dimethyl-α″-acetic acid)-trithiocarbonate and 2-dodecylsulfanylthiocarbonylsulfanyl-2-methyl propionic acid) were used as the chain transfer agents in conjunction with 4,4′-azobis(4-cyanovaleric acid) and 2,2′azobis(2-methylpropionamidine) dihydrochloride as the initiating species. Poly(NIPAM) is a thermo-responsive polymer that has a sharp lower critical solution temperature (LCST). Herein, we investigated the aqueous solution behaviour of well defined p(NIPAM) prepared by the RAFT process as a function of molecular weight (degree of polymerization: 50, 100 and 200) and temperature. Furthermore, we examine the influence of varying concentrations of macromolecular species (neutral polyethylene glycol (M_n - 3400 g/mol) and ionic bovine serum albumin (M_n - 63 000 g/mol)) on the LCST of p(NIPAM). The aqueous solution behaviour was assessed by spectrophotometry, dynamic light scattering and surface tensiometry. The macromolecular additives was found to have a significant effect on the coil to globular transition of the lower molecular weight p(NIPAM).     

Practical optical resolution of dl-muscone using tartaric acid derivatives as a chiral auxiliary

A simple and practical synthesis of (R)-(−)-muscone was achieved by optical resolution of dl-muscone using tartaric acid derivatives. The acetalization of dl-muscone with N,N′-dibenzyl-l-tartaramide in the presence of Sc(OTf)₃ and methyl orthoformate furnished a diastereomeric mixture of acetals, which were readily separated by simple recrystallization. Diastereomerically pure acetal was hydrolyzed to give optically pure muscone and recovered N,N′-dibenzyl-l-tartaramide.     

Efficient one-pot formation of 4-N-substituted 2,4-dihydro-3H-1,2,4-triazolin-3-ones from primary amines using N′-(ethoxymethylene)hydrazinecarboxylic acid methyl ester

(E)-N′-(Ethoxymethylene)hydrazinecarboxylic acid methyl ester was synthesized in one step in good yield. This reagent was successfully applied to the one-pot synthesis of 4-substituted 2,4-dihydro-3H-1,2,4-triazolin-3-ones from readily available primary alkyl and aryl amines. This reaction process is relatively mild and easy to carry out. It is especially useful for the formation of sterically hindered triazolinones, which are otherwise difficult to obtain via existing literature procedures. A possible mechanistic pathway for the transformation is outlined.     

3-Oxyanthranilic acid derivatives from Actinomadura sp. BCC27169

Eight new compounds including 9′-[2-amino-3-(4″-O-methyl-α-rhamnopyranosyloxy) phenyl]nonanoic acid (1), 9′-[2-amino-3-(4″-O-methyl-α-ribopyranosyloxy)phenyl] nonanoic acid (2), 11′-[2-amino-3-(4″-O-methyl-α-rhamnopyranosyloxy)phenyl]undecanoic acid (3), 11′-[2-amino-3-(4″-O-methyl-α-ribopyranosyloxy)phenyl]undecanoic acid (4), 8-(4′-O-methyl-α-rhamnopyranosyloxy)-3,4-dihydroquinolin-2(1H)-one (5), 8-(4′-O-methyl-α-ribopyranosyloxy)-3,4-dihydroquinolin-2(1H)-one (6), 8-(4′-O-methyl-α-rhamnopyranosyloxy)-2-methyquinoline (7), and 8-(4′-O-methyl-α-ribopyranosyloxy)-2-methylquinoline (8) were isolated from Actinomadura sp. BCC27169. The chemical structures of these compounds were determined based on NMR and high-resolution mass spectroscopy. The absolute configurations of these monosaccharides were revealed by the hydrolysis of compounds 7 and 8. Compounds 3 and 8 exhibited antitubercular activity at MIC 50 μg/mL. Only compound 3 showed cytotoxicity against KB cell at IC₅₀ 18.63 μg/mL, while other isolated compounds were inactive at tested maximum concentration (50 μg/mL).     

Reactivity of cyclopropanic δ-oxo-α,β-unsaturated esters towards SmI2: 3-exo-trig cyclisation versus cyclopropane ring opening

trans-(2′,2′-Diphenyl-bicyclopropyl-2-yl)-4,4-dimethyl-5-oxo-pent-2-enoic acid methyl ester 9, undergoes 3-exo-trig cyclisation in the presence of SmI₂ without competitive ring opening of Newcomb's bicyclopropylic probe next to the carbonyl group. From this result, it may be concluded that the absence of ring opening observed earlier in the case of 5-cyclopropyl-4,4-dimethyl-5-oxo-pent-2-enoate 7 is not due to the potentially reversible character of this process. Meanwhile, as deduced from kinetic considerations based on data of the literature, the absence of ring opening does not necessarily mean that formation of ketyl radicals is not involved in the 3-exo-trig cyclisations of δ-oxo-α,β-unsaturated esters.Compounds 7 and 9 cyclise with total syn selectivity, leading ultimately to lactones. This syn selectivity contrasts with that of other alkylic δ-oxo-α,β-unsaturated esters.     

A simple route to derivatives of benzo[j]fluoranthene

3,6,8,11-Tetramethoxybenzo[j]fluoranthene can be made from 1,6-dimethoxynaphthalene in a one-pot ferric chloride oxidation/methanol reduction procedure. The reaction is tolerant of the presence of substituents in the 7-position of the naphthalene nucleus and provides a quick and easy route to these particular benzo[j]fluoranthenes. The reactions presumably proceed through initial formation of a bond between the 4-positions of two naphthalene molecules followed by closure of the five-membered ring. Indeed in one case some 4,4′-binaphthyl was isolated from the reaction mixture and it was generally found that better yields of the benzo[j]fluoranthrenes were obtained starting from the 4,4′-binaphthyl rather than by using the naphthalene as the starting material. In an analogous manner to the ring-closure of the 4,4′-binaphthyls, starting from a hexakisalkoxyphenylnaphthalene, a hexakisalkoxyfluoranthene could be obtained.     

Solvent-free oxidation of alcohols by t-butyl hydroperoxide catalyzed by water-soluble copper complex

The catalytic system composed of CuCl₂ and 2,2′-biquinoline-4,4′-dicarboxylic acid dipotassium salt (BQC), was found to be highly efficient for the selective oxidation of secondary benzylic, allylic and propargylic alcohols to the corresponding ketones, with aqueous t-butyl hydroperoxide under phase-transfer catalysis conditions. The catalytic system is stable and can be recycled and reused several times without loss of activity.     

Novel optically active poly(amide-imide)s from N,N-(4,4-carbonyldiphthaloyl)-bis-l-phenylalanine diacid chloride and aromatic diamines by microwave irradiation

3,3^′,4,4^′-benzophenonetetracarboxylic dianhydride (4,4^′-carbonyldiphthalic anhydride) (1) was reacted with l-phenylalanine (2) in a mixture of acetic acid and pyridine (3:2) and the resulting imide-acid [N,N^′-(4,4^′-carbonyldiphthaloyl)-bis-l-phenylalanine diacid] (4) was obtained in high yield. The compound (4) was converted to the N,N^′-(4,4^′-carbonyldiphthaloyl)-bis-l-phenylalanine diacid chloride (5) by reaction with thionyl chloride. A new facile and rapid polycondensation reaction of this diacid chloride (5) with several aromatic diamines such as 4,4^′-diaminodiphenyl methane (6a), 2,4-diaminotoluene (6b), 4,4^′-sulfonyldianiline (6c), p-phenylenediamine (6d), 4,4^′-diaminodiphenylether (6e), m-phenylenediamine (6f), benzidine (6g) and 2,6-diaminopyridine (6h) was developed by using a domestic microwave oven in the presence of a small amount of a polar organic medium such as o-cresol. The polymerization reactions proceeded rapidly, compared with the conventional solution polycondensation, and was completed within 7 min, producing a series of optically active poly(amide-imide)s with high yield and inherent viscosity of 0.22-0.52 dl/g. All of the above polymers were fully characterized by IR, elemental analyses and specific rotation. Some structural characterization and physical properties of this optically active poly(amide-imide)s are reported.     

Synthesis and characterization of spin-coatable tert-amine molecules for hole-transport in organic light-emitting diodes

The synthesis of two tert-amine-based, non-fluorescent, hole-transport molecules (4,4′-[bis-{(4-di-n-hexylamino)benzylideneamino)]stilbene (DHABS) and 4,4′-[bis-{(4-diphenylamino)benzylideneamino}]stilbene) (DPABS) that are suitable for spin coating on indium tin oxide (ITO) for electronic device fabrication is described and compared with the widely used TPD. Electroluminescence occurred at a turn-on voltage of 7-8 V in ITO/hole-transport layer (HTL, spin coated)/Alq₃/Al devices.     

Synthesis, crystal structures and the preliminary evaluation of the new dibenzotetraaza[14]annulene-based DNA/RNA binding agents

A series of water-soluble dicationic dibenzotetraaza[14]annulenes have been prepared in order to examine their interactions with nucleic acids. Pendant water-solubilizing N-pyridinium, 4,4′-bipyridinium and N-methyl pyridinium moieties have been attached to the central core via linkers generated by direct N-alkylations and ester creating couplings, respectively. The crystal structures of derivatives equipped with 3-(N-pyridinium-1-yl)propyl and 3-(4,4′-bipyridinium-1-yl)propyl substituents have been determined. Interactions with ct-DNA have been studied and evidenced by means of spectrophotometric titrations with Scatchard analysis and thermal denaturation experiments.     

Convenient one-pot procedure for synthesizing 4,4′-dimethoxy-boradiaza-s-indacene dyes and their application to cell labeling

We succeeded in developing a convenient one-pot pathway for synthesizing 4,4′-dimethoxy-boradiaza-s-indacene dyes 4a-d. The structures feature two methoxy groups in place of the fluorine atoms in 4,4′-difluoro-4-boradiaza-s-indacene. These novel dyes emitted green fluorescence and possessed moderate to high fluorescence quantum yields (Φ=0.32-0.93). We demonstrated that these dyes have applicability to cell labeling.     

6,7,14,15-Tetrahydro[1,5]diazocino[1,2-a:6,5-a′]diindole. Synthesis of a novel pentacyclic ring system

In search of new lead structures for potent allosteric enhancers of antagonist binding to muscarinic M₂ receptors, the first representative of a novel heterocyclic ring system, 6,7,14,15-tetrahydro[1,5]diazocino[1,2-a:6,5-a′]diindole, has been synthesized. The new pentacyclic ring skeleton is obtained from [3-(2-dibenzylaminoethyl)indol-2-yl]-acetic acid methyl ester in three steps.