One-pot multistep synthesis of 4-acetoxy-2-amino-3-arylbenzofurans from 1-aryl-2-nitroethylenes and cyclohexane-1,3-diones

[reaction: see text] A novel method for synthesizing 4-acetoxy-2-amino-3-arylbenzofurans (4) from 1-aryl-2-nitroethylenes (1) and cyclohexane-1,3-diones (2) is described. The method features one-pot operation of a solution of 1 and 2 in THF with catalytic Et3N (rt, 12 h) followed with Ac2O, Et3N, and DMAP (rt, 5 h), although the process consists of 13 elementary reactions.     

Ce(iv)-centered charge-neutral perovskite layers topochemically derived from anionic [CeTa2O7]− layers

Layered perovskites have been extensively investigated in many research fields, such as electronics, catalysis, optics, energy, and magnetics, because of the fascinating chemical properties that are generated by the specific structural features of perovskite frameworks. Furthermore, the interlayers of these structures can be chemically modified through ion exchange to form nanosheets. To further expand the modification of layered perovskites, we have demonstrated an advance in the new structural concept of layered perovskite “charge-neutral perovskite layers” by manipulating the perovskite layer itself. A charge-neutral perovskite layer in [Ce^IVTa₂O₇] was synthesized through a soft chemical oxidative reaction based on anionic [Ce^IIITa₂O₇]⁻ layers. The Ce oxidation state for the charge-neutral [Ce^IVTa₂O₇] layers was found to be tetravalent by X-ray absorption fine structure (XAFS) analysis. The atomic arrangements were determined through scattering transmission electron microscopy and extended XAFS (EXAFS) analysis. The framework structure was simulated through density functional theory (DFT) calculations, the results of which were in good agreement with those of the EXAFS spectra quantitative analysis. The anionic [Ce^IIITa₂O₇]⁻ layers exhibited optical absorption in the near infrared (NIR) region at approximately 1000 nm, whereas the level of NIR absorption decreased in the [Ce^IVTa₂O₇] charge-neutral layer due to the disappearance of the Ce 4f electrons. In addition, the chemical reactivity of the charge-neutral [Ce^IVTa₂O₇] layers was investigated by chemical reduction with ascorbic acid, resulting in the reduction of the [Ce^IVTa₂O₇] layers to form anionic [Ce^IIITa₂O₇]⁻ layers. Furthermore, the anionic [Ce^IIITa₂O₇]⁻ layers exhibited redox activity which the Ce in the perovskite unit can be electrochemically oxidized and reduced. The synthesis of the “charge-neutral” perovskite layer indicated that diverse features were generated by systematically tuning the electronic structure through the redox control of Ce; such diverse features have not been found in conventional layered perovskites. This study could demonstrate the potential for developing innovative, unique functional materials with perovskite structures.

This study proposed a new layer modification technique, “layer charge control”, for layered perovskites, and the structures of the obtained charge neutral [CeTa₂O₇] perovskite sheet were characterized theoretically and experimentally.     

Chirally autocatalytic reaction performed in highly supersaturated conditions

Spontaneous chiral asymmetry generation, which is the preferential production of one enantiomer in a non‐chiral environment by chiral autocatalysis, could be observed in a preparation of a octahedral cobalt complex, cis‐[CoBr(NH₃)(en)₂]Br₂. A concentration fluctuation in a far‐from‐equilibrium chemical system will grow if the rate of local autocatalytic production of a compound in a small volume overcomes its loss due to diffusion. In a chirally autocatalytic system, this phenomenon could produce a large variation in the enantiomeric excess. In a reaction that produces the cobalt complex, the reaction rate was found to increase in the highly supersaturated solution of the product. In supersaturated solutions, before crystals of the solute have nucleated, embryos, which are the clusters of the solute, are formed. Ternary water‐solubility isotherm of each enantiomer of the cobalt complex suggests that each embryo consists of one exclusive enantiomer. Each chiral cluster, which could be regarded as polymeric material, thus formed in a highly supersaturated solution, may act as catalyst for the production of the same enantiomer. Life is a far‐from‐equilibrium self‐organized polymeric system in which chiral symmetry is broken. This reaction system is thus a model for the generation and amplification of chiral asymmetry in polymeric materials; it provides some insight in to the mechanisms that might have produced the observed biomolecular homochirality.     

Preparation and porous control of amorphous carbons by co-defluorination of perfluorooctane and octafluorotoluene in vapor phases at 423 K

Two types of perfluorocarbon compounds, aliphatic perfluorooctane and aromatic octafluorotoluene, were co-defluorinated using sodium metal, and amorphous carbons were deposited from the vapor phase at very low temperature, 423 K. The products showed morphologies composed of fibrous, platelet, and spherical forms, which were dependent on the mixing ratio of the two. The BET surface areas also correlated well with the ratio of the starting mixtures, indicating that the surface area could be adjusted by changing the mixing ratio of these two compounds. However, when the carbonaceous product was further annealed in situ at 573 or 673 K, the porosities also modified. First the porosity decreased at 573 K, then increased greatly at 673 K, where radical interaction to shrink the pores and crystal growth of template fluoride occurred at 573 K and 673 K, respectively.     

Synthesis and biological evaluation of γ-fluoro-β,γ-unsaturated acids

Several γ-fluoro-β,γ-unsaturated acids, fluorine-containing analogues of N-acyl glycines, were synthesized via Julia-Lythgoe olefination. The antimicrobial activities of these compounds and synthetic intermediates were evaluated. Analogues with an octyl group showed in vitro antifungal activity agaist Penicillium chrysogenum IFO4626.     

Noether-Lefschetz locus for Beilinson-Hodge cycles I

We discuss the Noether-Lefschetz locus for Beilinson's Hodge cycles. Here ``Beilinson's Hodge cycles' mean the cohomology class of Bloch's higher Chow cycles on smooth varieties. The main result is to give an estimate of the dimension of the maximal component of the Noether-Lefschetz locus for the universal family of open complete intersections.     

The fast measurement of head related impulse responses for all azimuthal directions using the continuous measurement method with a servo-swiveled chair

This paper proposes a method for the fast measurement of head related impulse responses (HRIRs) for all azimuthal directions using the continuous measurement method with a subject sitting on a servo-swiveled chair (SSC). The subject faces all azimuthal directions with a constant angular speed as the SSC rotates and hears corresponding spatial sounds. In our continuous measurement method, we use a maximum length sequence (MLS) as the excitation signal, record binaural signals using tiny microphones placed in the subject’s ear canal around 5 mm from the entrance, and feed them, along with the MLS signal, into a PC so that HRIRs can be extracted for all azimuthal directions and discrete elevations. In this paper, the underlying principles behind the method are described and conditions for successful implementation are examined through numerical simulations. Further, the validity of the proposed method is verified using a physical realization and empirical measurements.