On-line delta(18)O measurement of organic and inorganic substances

A method for the automated sample conversion and on-line oxygen isotope ratio (delta(18)O) determination for organic and inorganic substances is presented. The samples are pyrolytically decomposed at 1400 degrees C in the presence of nickelized graphite. With the system presented organic as well as inorganic samples such as nitrates, sulphates and phosphates of 50-100 &mgr;g O can be analyzed for their delta(18)O values with a standard deviation usually better than 0.5 per thousand. Additionally, carbon isotope ratios of organic substances and nitrogen isotope ratios of inorganic nitrogenous compounds are available in the same sample run. Data for international and some inter-laboratory reference materials are presented to show the accuracy and reliability of the method. The effect of some additives on the CO yield was checked for substances which do not pyrolyze completely. Copyright 1999 John Wiley & Sons, Ltd.     

Synthesis of Triazole Click Ligands for Suzuki-Miyaura Cross-Coupling of Aryl Chlorides

Russian Journal of Organic Chemistry - A series of new triazole ligands has been synthesized via copper-catalyzed cycloaddition reaction of readily available azides and alkynes. The synthesized...     

Bis(indenyl)titanium(IV) and zirconium(IV) complexes of monofunctional bidentate salicylidimines

Dichlorobis(indenyl)-titanium(IV) and -zirconium(IV), (C₉H₇)₂TiCl₂ and (C₉H₇)₂ZrCl₂, react with bidentate Schiff bases such as salicylidene aniline, salicylidene-o-toluidine, salicylidene-m-toluidine and salicylidene-p-toluidine in a 1:1 molar ratio in refluxing tetrahydrofuran in the presence of triethylamine to yield complexes of the type (C₉H₇)₂Ti(SB)Cl and (C₉H₇)₂Zr(SB)Cl, respectively where SB is the anion of the corresponding Schiff base, SBH. The new derivatives have been characterised on the basis of their elemental analyses, conductance measurements and spectral (IR, ¹H NMR and electronic) studies.     

Synthesis of fluorinated 2,3-dihydropyran-4-ones by cyclocondensation of 1,3-dicarbonyl dianions with aldehydes

The reaction of the dianion of 1,1,1-trifluoro-pentane-2,4-dione with aldehydes and subsequent addition of hydrochloric acid afforded 2,3-dihydro-6-trifluoromethyl-pyran-4-ones. The reaction of the dianion of acetylacetone with fluorinated benzaldehydes gave the corresponding fluorinated 2-aryl-2,3-dihydro-6-methyl-pyran-4-ones. All reactions proceeded in very good yield and with very good regioselectivity.     

Site-selective Suzuki-Miyaura cross-coupling reactions of 2,3,4,5-tetrabromofuran

Suzuki-Miyaura reactions of 2,3,4,5-tetrabromofuran allow a convenient and site-selective synthesis of mono-, di- and tetraarylfurans which are not readily available by other methods.     

Chelation-control in the formal [3+3] cyclization of 1,3-bis-(silyloxy)-1,3-butadienes with 1-hydroxy-5-silyloxy-hex-4-en-3-ones. One-pot synthesis of 3-aryl-3,4-dihydroisocoumarins

The [3+3] cyclization of 1,3-bis(silyloxy)-1,3-butadienes with 1-hydroxy-5-silyloxy-hex-4-en-3-ones resulted in the one-pot formation of 3-aryl-3,4-dihydroisocoumarins. The reactions proceeded by regioselective cyclization to give 6-(2-aryl-2-chloroethyl)salicylates, which underwent a silica gel-mediated lactonization. The cyclizations of protected 1-amino-5-silyloxy-hex-4-en-3-ones proved to be not regioselective.