Stereoselective construction of a quaternary carbon substituted with multifunctional groups: application to the concise synthesis of (+)-ethosuximide

Synthetically useful β,γ-unsaturated carbonyl compounds having a quaternary carbon at the -position were prepared with high stereoselectivity by the reaction of a dienolate anion derived from ,β-unsaturated imide having a chiral auxiliary and electrophiles (ethyl acetate and allyl iodide as the C₂ and C₃ unit, respectively). This method was applied to a short asymmetric synthesis of (+)-ethosuximide.     

Cobalt-catalyzed intramolecular Heck-type reaction of 6-halo-1-hexene derivatives

[reaction: see text] Treatment of 6-iodo-1-hexene derivatives with trimethylsilylmethyl Grignard reagent in the presence of CoCl(2)(dppb) in refluxing THF affords Heck-type products, methylenecyclopentanes, in good yields.     

Exchange interaction in covalently bonded biradical-monoradical composite molecules

As a novel molecular designing for genuinely organic molecule-based ferrimagnets, we have proposed a strategy of "single-component ferrimagnetics". When a pi-biradical with an S = 1 ground state and a pi-monoradical with S = (1)/(2) are united by sigma-bonds, the pi-conjugation between the biradical and the monoradical moieties should be truncated in the resultant triradical. This gives magnetic degrees of freedom for both S = 1 and (1)/(2) in the single molecule, serving as a building block for organic molecule-based ferrimagnets under favorable conditions (single-component ferrimagnetics). We have designed and synthesized a triradical, 3-(1'-oxyl-3'-oxido-4',4',5',5'-tetramethylimidazolin-2-yl)benzoic acid 2,4-bis(1' '-oxyl-3' '-oxido-4' ',4' ',5' ',5' '-tetramethylimidazolin-2-yl)phenyl ester (4), as a model compound for the novel approach to genuinely organic ferrimagnets. In the triradical 4, a m-phenylene-bis(nitronyl nitroxide) biradical with a triplet (S = 1) ground state is united with a phenyl nitronyl nitroxide monoradical (S = (1)/(2)) by an ester coupler. Solution-phase ESR spectra from 4 exhibited a complex hyperfine splitting due to (14)N and (1)H nuclei. The analysis of the hyperfine structure based on perturbation calculations has revealed that the exchange interaction within the biradical moiety is much larger than those between the biradical and the monoradical moieties and the magnetic degrees of freedom for both S = 1 and (1)/(2) are retained in 4. An X-ray crystal structure analysis showed that the triradical molecules are arranged in a one-dimensional molecular chain in the crystal. The magnetic susceptibility in a crystalline solid state is consistent with the crystal structure.     

A SAXS observation of the crystallization of an Al85Y10Ni5 amorphous alloy in the supercooled liquid state

The medium-range structure of a heat-treated Al₈₅Y₁₀Ni₅ amorphous alloy was investigated by small-angle X-ray scattering, calorimetric analysis, wide-angle X-ray diffraction and transmission electron microscope measurements. It is observed that crystalline particles having a definite boundary are precipitated by annealing at supercooled liquid temperatures and that most of the precipitates consist of the Al fcc crystalline phase. The integrated intensities of the small-angle scattering and the Guinier radii of the precipitates increase on annealing for time duration <5.4 ks. However, as the annealing time becomes > 5.4 ks, the integrated intensities and the Guinier radii are invariant, i.e., growth of the precipitates ceases. After annealing for 518.4 ks, the diameters of the precipitates exhibit a narrow distribution centered around 200 Å.     

An azonia derivative of hexahelicene

In 8a‐azonia­[6]­helicene hexa­fluoro­phos­phate or 8a‐azoniaphenanthro[3,4‐c]phen­an­threne hexa­fluoro­phos­phate, C₂₅H₁₆N⁺·PF₆⁻, replacement of an outer bridgehead carbon of hexahelicene by a quaternary Nsp² atom results in a geometrical change in the helical structure. The racemic heterohelicene forms homochiral columnar stacks through intermolecular π–π donor–acceptor interactions in the crystalline state.     

Trinuclear coordinatively labile Cu(II) complex of 4,6-O-ethylidene-beta-D-glucopyranosylamine derived Schiff base ligand and its reactivity towards primary alcohols and amines

A novel neutral trinuclear Cu(II) complex of a Schiff base ligand derived from D-glucose has been synthesised and structurally characterised, which exhibits excellent alcohol binding affinity and activates the C-Cl bond of chloroform in the presence of primary amine.     

Cp*RuCl-catalyzed [2 + 2 + 2] cycloadditions of alpha,omega-diynes with electron-deficient carbon-heteroatom multiple bonds leading to heterocycles

In the presence of a catalytic amount of Cp*RuCl(cod), 1,6-diynes were allowed to react chemo- and regioselectively with electron-deficient nitriles and heterocumulenes at 60-90 degrees C to afford heterocyclic compounds. The mechanism of the ruthenium-catalyzed regioselective formations of bicyclic pyridines and pyridones were analyzed on the basis of density functional calculations. Cyclocotrimerizations of ethyl propiolate with ethyl cyanoformate or propyl isocyanate gave rise to two of the four possible pyridine or pyridone regioisomers.     

Domino coupling relay approach to polycyclic pyrrole-2-carboxylates

CuBr2-catalyzed three-component coupling of N-benzylallylamine, ethyl glyoxalate, and terminal alkynes afforded glycine-tethered 1,6-enynes, which were further transformed into polycyclic pyrrole-2-carboxylates via novel cycloisomerization/Diels-Alder cycloaddition/dehydrogenation sequence under iridium-catalyzed conditions.