NOVEL HALOGENATION OF THIOPHENES WITH BENZENESELENINYL CHLORIDE AND ALUMINUM HALIDE

Abstract

In the presence of aluminum halide, benzeneseleninyl chloride is an efficient Regioselective halogenating reagent for heterocyclic compounds such as thiophene, 2methylthiophene. 3-methylthiophene, 2,5-dimethylthiophene, and furan. In the case of pyrrole, no halogenated product was obtained. A plausible reaction mechanism involving a positive halogen intermediate is proposed.     

Simultaneous manifestation of metallic conductivity and single-molecule magnetism in a layered molecule-based compound

Single-molecule magnets (SMMs) show superparamagnetic behaviour below blocking temperature at the molecular scale, so they exhibit large magnetic density compared to the conventional magnets. Combining SMMs and molecular conductors in one compound will bring about new physical phenomena, however, the synergetic effects between them still remain unexplored. Here we present a layered molecule-based compound, β′′-(BEDO-TTF)₄ [Co(pdms)₂]·3H₂O (BO4), (BEDO-TTF (BO) and H₂pdms are bis(ethylenedioxy)tetrathiafulvalene and 1,2-bis(methanesulfonamido)benzene, respectively), which was synthesized by using an electrochemical approach and studied by using crystal X-ray diffraction. This compound simultaneously exhibited metallic conductivity and SMM behaviour up to 11 K for the first time. The highest electrical conductivity was 400–650 S cm⁻¹ at 6.5 K, which is the highest among those reported so far for conducting SMM materials. Furthermore, antiferromagnetic ordering occurred below 6.5 K, along with a decrease in conductivity, and the angle-independent negative magnetoresistance suggested an effective electron correlation between the conducting BO and Co(pdms)₂ SMM layers (d–π interactions). The strong magnetic anisotropy and two-dimensional conducting plane play key roles in the low-temperature antiferromagnetic semiconducting state. BO4 is the first compound exhibiting antiferromagnetic ordering among SMMs mediated by π-electrons, demonstrating the synergetic effects between SMMs and molecular conductors.

A metallic single-molecule magnet was synthesised demonstrating simultaneous metallic conduction and excellent SMM properties at the same temperature range for the first time, with potential applications in molecule-based quantum spintronics.     

Attempted synthesis of axial-equatorial pyrazine-bridged copper(II) complexes toward homometallic ferromagnetic compounds

The introduction of a relatively bulky alkyl group at 2-position of pyrazine afforded unique μ-pyz complexes, namely, dinuclear [{Cu(hfac)₂}₂(μ-2-isobutylpyrazine)], trinuclear [{Cu(hfac)₂}₃(μ-2-isopropylpyrazine)₂], and polymeric [Cu(hfac)₂(μ-ibupyz)]_n (Hhfac stands for 1,1,1,5,5,5-hexafluoropentane-2,4-dione). These compounds have an axial-equatorial dinuclear moiety, which is expected to show ferromagnetic interaction. However, they exhibited practically negligible or very weak antiferromagnetic interaction. This may be due to violation of orthogonality because of the steric hindrance of the isobutyl or isopropyl groups. We analyzed the relationship between the structural deformation parameter defined as the N(eq)?N(ax)-Cu angle and the exchange coupling parameter. A critical angle, at which the sign of the magnetic coupling changes from positive to negative, is estimated to be 165(2)°. The present results are reasonably explained in this relation.     

Total synthesis of (+)-UCS1025A based on a sequential Michael-retro Michael strategy featuring one-pot six-step cascade reaction

The asymmetric total synthesis of UCS1025A is accomplished by establishing a novel and efficient method for the construction of a tricyclic pyrrolizidinone skeleton based on a sequential Michael-retro Michael strategy. The key step is a one-pot six-step cascade reaction including oxidation of a primary alcohol to the corresponding carboxylic acid, a retro thio-Michael reaction, and an intramolecular oxy-Michael reaction. This newly-developed synthetic strategy inspired by “masked” electrophilic character of tricyclic pyrrolizidinone is efficient and high-yielding compared to that developed in previously-reported total syntheses.