Synthesis and x-ray characterization of the [Ir6(CO)15COEt]-Anionic Cluster

The reaction of Ir₆(CO)₁₆ with a mixture of CO, H₂, and ethylene yields the [Ir₆(CO)₁₅COEt]^- anion, which has been shown by X-ray diffraction to contain an octahedral iridium cluster bearing a —bonded acyl group; the arrangement of the 11 terminal and 4 edge-bridging carbonyl groups is different from that found in both the analogous rhodium complex and the parent Ir₆(CO)₁₆ carbonyl.     

Reaction of substituted sulfenes with N,N-disubstituted α-amino-methyleneketones. I. Synthesis of N,N-disubstituted cis- and trans-4-amino-3,4,5,6,7,8-hexahydro-3-phenyl-1,2-benzoxathiin 2,2-dioxides

The polar 1, 4-cycloaddition of phenylsulfene (generated in situ from phenylmethanesulfony] chloride and triethylamine) to N, N-disubstituted (E)-2-aminomethylenecyclohexanones I gave in general a mixture of N, N-disubstituted cis- and trans-4-amino-3, 4, 5, 6, 7, 8-hexahydro-3-phenyl-1, 2-benzoxathiin 2, 2-dioxides III and IV, which were separated by column chromatography and whose structural and conformational features were determined from uv, ir and nmr spectral data. In the case of N, N-diisopropylamino enaminone 1c, the cyclo-addition took place with elimination of an alkyl group as propene to give the adduct III?.     

Synthetic Applications of 2-(1,3-Dithian-2-yl)indoles. 7. Synthesis of Aspidospermidine

A new method of synthesizing the alkaloid aspidospermidine (1), based on building ring E on the pyridocarbazole [ABCD] ring structure, is reported. The preparation of the pyridocarbazole framework of Aspidosperma alkaloids is a new three-step synthetic application of 2-(1,3-dithian-2-yl)indoles. A tandem conjugate addition-alkylation reaction starting from indolyldithiane (4), 3-methylenelactam 6, and EtI yields the adduct 17. Treatment of lactam 17 with DIBALH leads to formation of the naphthyridoindole 18. Compound 18 isomerizes in aqueous AcOH to yield pyridocarbazole 3. Finally, closure of ring E and subsequent reduction of the dithiane ring produces aspidospermidine. Pyridocarbazoles 2 and 10 were prepared as models.     

Synthesis of di‐ and triblock copolymers of styrene and butyl acrylate by controlled atom transfer radical polymerization

Di‐ and triblock copolymers of styrene and butyl acrylate with controlled molar masses (M_n up to ≈ 10⁵) were sequentially prepared by radical atom transfer polymerization in a homogeneous medium using chlorine end capped polymers as initiators and the copper^(I) chloride/bipyridine complex as catalyst, in the presence of dimethylformamide. Random poly(styrene‐co‐butyl acrylate) was synthesized and the cross‐over reactions between Cl end capped polystyrene and poly(butyl acrylate) to the opposite monomers were examined.     

Synthesis of 5-cyanopyrazolo[3,4-b]pyridines in the reaction of 5-amino-3-methyl-1-phenylpyrazole with arylidene derivatives of malonodinitrile and ethyl cyanoacetate

This paper describes the synthesis of a new series of 6-amino-4-aryl-5-cyanopyrazolo[3,4-b]pyridines 4 and 4-aryl-5-cyano-6H-pyrazolo[3,4-b]pyridin-6-ones 5 from the reaction of 5-amino-3-methyl-1-phenylpyrazole 1 with arylidene derivatives of malonodinitrile 2 and ethyl cyanoacetate 3 . The structure of the final compounds was determined on the basis of nmr measurements, especially by ¹H, ¹H-, ¹H, ¹³C-COSY, DEPT and X-ray diffraction.     

Spatial distribution profiles of magnesium and strontium in speleothems using laser-induced breakdown spectrometry

Laser-induced breakdown spectrometry (LIBS) has been applied to spatially locate several atomic species in speleothems taken from the Nerja’s Cave (Málaga, Spain). Spatial distribution profiles of Mg at 285.21 nm and Sr at 407.77 nm were obtained while the laser was rastered through different paths along the sample. These elements were selected due to their importance as palaeoclimatic indicators. The 532 nm output of a Nd:YAG laser was used to irradiate the samples and generate the plasma that was spectrally analyzed and detected by using an intensified CCD detector. The signals were normalized to the Ca line to minimize pulse-to-pulse fluctuations in the laser source. Several studies were carried out to check for the point-to-point heterogeneity of the natural speleothem.     

Analytic gradients in the improved BCS method

The first derivatives of the total energy with respect to nuclear displacement have been calculated in the framework of the Improved Bardeen–Cooper–Schrieffer (IBCS) method. It permits the quick determination of the stationary points. This revised version was published online in July 2006 with corrections to the Cover Date.