Gas Chromatographic Separation of Carbonyl Compounds as Their 2,4-dinitrophenylhydrazones Using Glass Capillary Columns

The gas chromatographic separation of 22 carbonyl compounds as their 2,4-dinitrophenylhydrazones was investigated using glass capillary columns. Complete separation of the 2,4-dinitrophenylhydrazones of ten aliphatic aldehydes, eight aliphatic ketones and four aromatic aldehydes was obtained, except for the derivatives of n-valeraldehyde and isobutyl methyl ketone, whose peaks overlapped, and the o- and m-tolualdehyde derivatives, which were poorly separated. The optimum conditions were as follows: stationary phase, SF-96; column size, 20 m × 0.25 mm I.D. ; column temperature, 200-240°; injection and detector temperatures, 280-290°; carrier gas flow-rate, helium 1.0-1.2 ml/min or nitrogen 1.1-1.2 ml/min. The method was applied to the analysis of aliphatic carbonyl compounds in car exhaust fumes and cigarette smoke.     

Polymerization of methacrylates. I. Polymerization reactivity of picryl methacrylate

The polymerization of picryl (PMA), 2,4-dinitrophenyl (2,4-DNMA),2,6-dinitrophenyl (2,6-DNMA), 2-methyl-4,6-dinitrophenyl (MDNMA), and 2,6-dimethylphenyl methacrylates (DMMA) was carried out in benzene at 60°C. PMA, 2,6-DNMA, and MDNMA did not undergo radical homopolymerization, while 2,4-DNMA and DMMA did. The results suggest that the growing radical readily attacks the oxygen atom of the nitro group at the 2 position of the terminal phenyl group due to the steric effect of the substituent at the 6 position, resulting in chain termination. PMA formed a charge-transfer complex with 2-naphthyl methacrylate (NMA). The stoichiometric composition of this complex was shown to be 1:1 molar complex. PMA was readily copolymerized with NMA. The amount of solvent affected the composition of the copolymer obtained at a given same mole fraction in feed. The results suggest that charge-transfer interaction between the ester groups affects the copolymerization mechanism.     

PtBr2-catalyzed consecutive enyne metathesis-aromatization of 1-(1-methoxy-but-3-enyl)-2-(1-alkynyl)benzenes: dual role of the Pt catalyst

1,7-Enynes 1, connected through an aromatic ring and bearing a leaving methoxy group at the 4-position, underwent the PtBr(2)-catalyzed enyne metathesis followed by aromatization in one pot to afford vinyl naphthalenes 3 in good to acceptable yields. The cyclobutene intermediate 11a and another intermediate 2a were isolated, indicating that PtBr(2) acts as a dual role catalyst: (1) as a transition metal catalyst, it induces the enyne metathesis to produce 11a starting from 1a, and (2) as a Lewis acid catalyst, it facilitates elimination of MeOH from 2a to give the aromatized product 3a.     

Cu(I) catalyst in DMF: an efficient catalytic system for the synthesis of furans from 2-(1-alkynyl)-2-alken-1-ones

The cyclization of 2-(1-alkynyl)-2-alken-1-ones 1 proceeded very smoothly in the presence of alcohols 2 with a catalytic amount of Cu(I)Br in DMF at 80 degrees C, leading to the formation of highly substituted furans 3. The catalytic system reported herein is easy to handle, compared to the previously known system wherein the reaction between 1 and 2 needed to use moisture sensitive gold(III) chloride.     

Reaction of enaminones with carbon disulfide: Synthesis of heterocycles using enamino dithiocarboxylates

Reaction of various types of enaminones, which are prepared by the condensation of 1,3-dicarbonyl compounds with aromatic amines, with carbon disulfide in the presence of sodium hydroxide as the base in dimethyl sulfoxide to give the corresponding enamino dithiocarboxylates, 1,3-thiazines and trithiones. Enamino dithiocarboxylates are cyclized under refluxing in diphenyl ether to give the fused quinoline derivatives. The reaction of 6-arylamino-1,3-dimethyluracils with excess carbon disulfide in the presence of sodium hydroxide and subsequent methylation with dimethyl sulfate gave directly the corresponding 1,3-dimethyl-5-methylthiopyrimido[4,5-b]quinoline-2,4(1H,3H)-diones.     

Elongation and contraction of molecular springs. Synthesis, structures, and properties of bridged [7]thiaheterohelicenes

A series of bridged [7]thiaheterohelicenes 3a-c and 4 with a variety of helical pitches have been prepared from racemic and optical pure 2,13-bis(hydroxymethyl)dithieno[3,2-e:3',2'-e']benzo[1,2-b:4,3-b']bis[1]benzothiophene (1) in order to investigate the helical structures in solution. Recrystallizations of (PM)-3a, (PM)-3b, (PM)-3c, and (P)-4 from hexane-dichloromethane gave crystals suitable for X-ray crystallography, while recrystallization of (PM)-4 with benzene gave an inclusion complex with a stoichiometry of (PM-4)(4).(C(6)H(6)). X-ray analyses of (PM)-3a-c, (PM-4)(4).(C(6)H(6)), and (P)-4 indicate that the dihedral angles between terminal thiophene rings of the helical framework significantly vary from 22 degrees for 4 to 59 degrees for 3c. This represents as increase of 37 degrees or 168%. Although the (13)C NMR and UV absorption spectra of bridged helicenes 3a-c and unbridged helicene 5 are essentially the same, the molar rotation of 5 is very large compared with those of 3a-c and 4. A red shift (15 nm) in the circular dichroism (CD) spectrum is observed for 4, suggesting that this compound is more planar than 3a-c in solution. In the series of [7]thiaheterohelicenes studied, the minimum helical pitch is 2.70 A for 4.     

Formation of Supramolecular Polymers Constructed by Cyclodextrins with Cinnamamide

-Cyclodextrin having cinnamamide at 6- or 3-positions (6-CiNH--CD, 3-CiNH--CD) and -cyclodextrin with cinnamamide on 6-position (6-CiNH--CD) have been prepared. Supramolecular structures were formed in the solid state or aqueous solutions and characterized by measurements of NMR and vapor pressure osmometry (VPO). The results indicate that 6-CiNH--CD formed insoluble supramolecular polymers in the solid state, while 6-CiNH--CD and 3-CiNH--CD formed supramolecular complexes in aqueous solutions. 6-CiNH--CD was found to form a dimer in an aqueous solution. 3-CiNH--CD formed intermolecular complexes to give supramolecular polymers. The differences of the position of guest part on cyclodextrins caused to give a variety of supramolecular structures in aqueous solutions.     

Pre-concentration of traces of tin by coprecipitation with yttrium hydroxide for electrothermal atomisation atomic absorption spectrometry

Summary Trace amounts of tin were concentrated by coprecipitation and determined by electrothermal atomisation atomic absorption spectrometry. Yttrium hydroxide coprecipitated quantitatively 0.1–3 g of tin from 50–500 ml of sample solution at pH 9.5–11.2. The atomic absorbance of tin increased about twice by using an impregnated graphite tube with yttrium. The impregnated graphite tube, furthermore, improved the reproducibility of the measurement of tin. A linear calibration graph was obtained in the range of 0.004–0.12 g/ml of tin. Twenty-three foreign ions did not interfere seriously. The method was applicable to the determination of tin in zinc metal.     

First synthesis of 1,9-dideoxyforskolin from ptychantin A

1,9-Dideoxyforskolin 2 has been synthesized starting from ptychantin A 3.