An efficient nitration of light alkanes and the alkyl side-chain of aromatic compounds with nitrogen dioxide and nitric acid catalyzed by N-hydroxyphthalimide

Nitration of light alkanes and the alkyl side-chain of aromatic compounds with NO(2) and HNO(3) was successfully achieved by the use of N-hydroxyphthalimide (NHPI) as a catalyst under relatively mild conditions. For example, the nitration of propane with NO(2) catalyzed by NHPI at 100 degrees C for 14 h gave 2-nitropropane in good yield without formation of 1-nitropropane and cleaved products such as nitroethane and nitromethane. Various aliphatic nitroalkanes, which are difficult to prepare by conventional methods, could be selectively obtained by means of the present methodology by using NHPI as the key catalyst. In addition, the side-chain nitration of alkylbenzenes such as toluene was selectively carried out to lead to alpha-nitrotoluene without the ring nitration. The present reaction provides an efficient selective method for the nitration of light alkanes and alkylbenzenes, which has been very difficult to carry out so far.     

Palladium-catalyzed transformation of cyclobutanone O-benzoyloximes to nitriles via C-C bond cleavage

Palladium-catalyzed transformation of cyclobutanone O-benzoyloximes to a variety of nitriles is described. The reaction may proceed via two important steps, that is, (i) oxidative addition of the N-O bond of oximes to Pd(0) to give a cyclobutylideneaminopalladium(II) species and (ii) beta-carbon elimination of this species to afford a reactive alkylpalladium species. The kind of products is very dependent on the nature of substituents on the cyclobutane ring. The direction of the C-C bond cleavage is controlled by the kind of ligand employed. The sequential reaction composed of the C-C bond cleavage and the subsequent intra- and intermolecular C-C bond formations via the corresponding alkylpalladium species is also demonstrated. For example, an oxime having an alkynyl moiety at a suitable position reacts with a variety of alkenes to afford nitriles bearing dienylcyclopentane moiety in moderate to good yields.     

Interconversion between bis(mu-thiolato)dicopper(II) and disulfide-bridged dicopper(I) complexes mediated by chloride ion

An unprecedented clean interconversion between a novel bis(mu-thiolato)dicopper(II) complex (1) and a disulfide-bridged dicopper(I) complex (3) through a disulfide-bridged (mu-chloro)dicopper(I) complex (2) mediated by chloride ion has been established for the first time, providing a new redox chemistry of the transition metal-sulfur complexes. Crystal structures of 1 and 3 as well as spectroscopic features of the compounds are reported.     

Microstructure of the copolymers of methyl methacrylate with other methacrylates obtained by radical and anionic copolymerizations in tetrahydrofuran

Monomer reactivity ratios r₁ and r₂ were determined in the copolymerizations of methyl methacrylate (MMA, M₁) with 1, 1-diphenylethyl (DPEMA), α,α-dimethylbenzyl (DMBMA), tert-butyl (t-BuMA), diphenylmethyl (DPMMA), phenyl (PhMA), and 1-naphthyl (NpMA) methacrylates (M₂) in tetrahydrofuran (THF) by azobisisobutyronitrile (AIBN) at 60°C and butyllithium (n-BuLi) at ?78°C. The reactivities of the monomers were explained in terms of the polar effect of the ester groups in both copolymerizations. All the copolymers isolated in low yields were converted to PMMA either directly or by copoly(MMA—methacrylic acid) to determine the triad tacticities of the copolymers. Coisotactic parameters σ₁₂ and σ₂₁ were determined by assuming the terminal model statistics. The σ₂₁ values always accorded to the σ₂₁ values within experimental error, and in radical copolymerizations they were between isotactic parameters σ₁₁ and σ₂₂ of the homopolymerizations of MMA and M₂ monomers. In anionic copolymerizations, however, the σ₁₂ = σ₂₁ values varied, depending on the M₂ monomers. In copolymerization with DPEMA the values were less than both σ₁₁ and σ₂₂ with DMBMA they were between σ₁₁ and σ₂₂, with DPMMA, nearly equal to σ₁₁, and with PhMA and NpMA, greater than both σ₁₁ and σ₂₂. The application of these parameters to copolymerizations performed at high conversion was also investigated.     

Preconcentration of chromium(III) and chromium(VI) in sea water by complexation with quinolin-8-ol and adsorption on macroporous resin

Chromium(III) is a sea water at the nanomole level was selectively collected using a column packed with macroporous polystyrene-divinylbenzene resin after complexation with quinolin-8-ol. Complex formation between ligand and inert hydrated chromium(III) ions was achieved by heating a sample solution containing a small amount of quinolin-8-ol for a short time in a microwave oven. Chromium(VI) was collected by a similar method after reducing it to chromium(III) with hydroxylamine. The effect of co-existing organic materials on the collection of chromium(III) and chromium(VI) was examined. This method was successfully applied to the determination of chromium(III) and chromium(VI) in sea water by graphite furnace AAS.     

Simultaneous determination of tungsten and molybdenum in sea water by catalytic current polarography after preconcentration on a resin column

The simultaneous determination of tungsten and molybdenum in sea water is based on preconcentration by column extraction with 7-(1-vinyl-3,3,5,5-tetramethylhexyl)-8-quinolinol (Kelex- 100) resin, and measurement of the polarographic catalytic currents obtained in a solution of chlorate, benzilic acid and 2-methyl-8-quinolinol. When the concentration factor is 50, the detection limits are 2.4 pM for tungsten and 17 pM for molybdenum (for a signal-to-noise ratio of 3). The precision of the determination is ca. 10% for 67 pM tungsten and ca. 5% for 106 nM molybdenum in sea water (n=4). Results for sea water and other natural waters are presented.     

Synthesis of optically active polymers containing chiral phosphorus atoms in the main chain

We successfully synthesized optically active polymers by using a chiral bisphosphine, (S,S)‐1,2‐bis[boranato(t‐butyl)methylphosphino]ethane, as a key building block. Their structures were characterized with ¹H, ¹³C, and ³¹P NMR spectra. The obtained polymers exhibited different glass‐transition temperatures depending on the structure of each comonomer, whereas a model compound had a melting point. According to circular dichroism spectra, the difference in the stereochemistry of the comonomers yielded the different higher‐ordered structures of the polymers induced by chiral phosphine units. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 866–872, 2007