Anomaly of specific heat due to kinks

Finite temperature corrections to classical kink free energies for the sine-Gordon and ø⁴ chains are obtained analytically by means of the transfer integral method. These corrections reveal that kink excitations cause a Schottky-type anomaly of specific heat at low temperatures. The numerical results of Schneider and Stoll are explained qualitatively.     

The syntheses of pteridin-2-one derivatives from diaminomaleonitrile (DAMN)

1,3-Dimethyl-4-iminopteridin-2-one, 1,3-dimethylpteridine-2,4-dione, 1-methylpteridine-2,4-dione, 4-alkoxy-1-methylpteridin-2-one, and 4-alkylamino-1-methylpteridin-2-one were synthesized from diaminomaleonitrile (DAMN) through pyrazine-2,3-dicarbonitrile. The synthetic procedures consist of the condensation of DAMN with glyoxal, the nucleophilic substitution of pyrazine-2,3-dicarbonitrile with methylamine, the reaction of 3-methylaminopyrazine-2-carbonitrile with electrophiles such as methyl isocyanate and methyl chloroformate in the presence of sodium hydride, and the transformation of 3-(methoxycarbonylmethyl)aminopyrazine-2-carbonitrile into the pteridine derivatives.     

The synthesis of benzofuroquinolines. V. Some benzofuro[3,2-B]quinoline derivatives

Some benzofuro[3,2-b]quinoline derivatives 1a-d and 3a were synthesized by condensation of 2-amino-benzaldehyde, 2-aminoacetophenone, 2-aminobenzophenone, isatin, or 2-aminobenzoic acid with 3(2H)-benzofuranone. The benzofuroquinolinone 3a was also obtained from 2-aminobenzoic acid and phenoxy-acetyl chloride in two steps and converted to 10-chloro derivative 1e . Similarly, some 8-halobenzofuro[3,2-b]-quinoline derivatives 1d,e and 3a (X = F, Cl, Br, I) were synthesized from 5-haloisatin or 2-amino-5-halo-benzoic acid. And benzofuro[3,2-b]quinolines 1a-e thus obtained were converted to corresponding N-oxides 2 .     

Palladium-catalyzed conjugate addition of organosiloxanes to alpha,beta-unsaturated carbonyl compounds and nitroalkenes

The addition of aryltrialkoxysilanes to alpha,beta-unsaturated carbonyl compounds (ketones, aldehydes) and nitroalkenes in the presence of SbCl(3), TBAF, AcOH, and a catalytic amount of Pd(OAc)(2), in CH(3)CN at 60 degrees C, provides the corresponding conjugate addition products in moderate to good yields. The addition of equimolar amounts of SbCl(3) and TBAF is necessary for this reaction to proceed smoothly. The arylpalladium complex, which is generated by the transmetalation from a putative hypercoordinate silicon compound, is considered to be the catalytically active species.     

1,3-Dipolar cycloaddition of α-alkoxycarbonylnitrones with vinyl ethers and allyl alcohols in the presence of Eu(fod)3: selective activation of (Z)-isomers of the nitrones

Uncatalyzed cycloaddition of α-alkoxycarbonylnitrones 1 with vinyl ethers 7 gave mixtures of cis- and trans-cycloadducts 8, whereas Eu(fod)₃-catalyzed cycloaddition of 1 with 7 gave the trans-cycloadducts trans-8 in a highly stereoselective manner. NMR studies indicated that Eu(fod)₃ selectively activated (Z)-nitrones (Z)-1 in E,Z-equilibrium mixtures of nitrones 1. In contrast, the reaction of 1 with allyl alcohols 12 in the presence of Eu(fod)₃ resulted in sequential transesterification and intramolecular cycloaddition to give intramolecular cycloadducts 13.     

Four (E,Z,E)‐1‐(4‐alkoxy­phen­yl)‐6‐(4‐nitro­phen­yl)hexa‐1,3,5‐trienes

The crystal structures of the four E,Z,E isomers of 1‐(4‐alk­oxy­phen­yl)‐6‐(4‐nitro­phen­yl)hexa‐1,3,5‐triene, namely (E,Z,E)‐1‐(4‐methoxy­phen­yl)‐6‐(4‐nitro­phen­yl)hexa‐1,3,5‐triene, C₁₉H₁₇NO₃, (E,Z,E)‐1‐(4‐ethoxy­phen­yl)‐6‐(4‐nitro­phen­yl)hexa‐1,3,5‐triene, C₂₀H₁₉NO₃, (E,Z,E)‐1‐(4‐nitro­phen­yl)‐6‐(4‐n‐propoxyphen­yl)hexa‐1,3,5‐triene, C₂₁H₂₁NO₃, and (E,Z,E)‐1‐(4‐n‐butoxy­phen­yl)‐6‐(4‐nitro­phen­yl)hexa‐1,3,5‐triene, C₂₂H₂₃NO₃, have been determined. Inter­molecular N⋯O dipole inter­actions between the nitro groups are observed for the meth­oxy derivative, while for the eth­oxy derivative, two adjacent mol­ecules are linked at both ends through N⋯O dipole–dipole inter­actions between the N atom of the nitro group and the O atom of the eth­oxy group to form a supra­molecular ring‐like structure. In the crystal structures of the n‐prop­oxy and n‐but­oxy derivatives, the shortest inter­molecular distances are those between the two O atoms of the alk­oxy groups. Thus, the nearest two mol­ecules form an S‐shaped supra­molecular dimer in these crystal structures.     

Room‐Temperature Phosphorescence of Crystalline Metal‐Free Organoboron Complex

The photoluminescence (PL) properties of a metal‐free organoboron complex, bis(4‐iodobenzoyl)methanatoboron difluoride ( 1BF₂ ), were elucidated. At room temperature, 1BF₂ emits blue fluorescence (FL) in nBuCl upon photoexcitation. In contrast, crystals of 1BF₂ emit green PL comprised of FL and phosphorescence (PH). The room‐temperature PH of crystalline 1BF₂ is a consequence of 1) suppression of thermal deactivation of the S₁ and T₁ excited states and 2) enhancement of intersystem crossing (ISC) from the S₁ to T₂ or T₁. The results of X‐ray crystallographic and theoretical studies supported the proposal that the former (1) is a result of intermolecular interactions caused by π‐stacking in the rigid crystal packing structure of 1BF₂ . The latter (2) is an effect of not only the heavy‐atom effect of iodine, but also the continuous π‐stacking alignment of 1BF₂ molecules in crystals, which leads to a forbidden S₁→S₀ transition and a small energy gap between the S₁ and T₂ or T₁.     

Asymmetric Synthesis of Chiral Sulfimides through the O-Alkylation of Enantioenriched Sulfinamides and Addition of Carbon Nucleophiles

Chiral sulfimides, the aza-analogues of sulfoxides, are valuable compounds in organic synthesis and medicinal chemistry. Herein, we report an efficient method for preparing chiral sulfimides from easily available enantioenriched sulfinamides. The key step of this method is a stereospecific oxygen-selective alkylation of enantioenriched sulfinamides, which is accomplished by using isopropyl iodide, K₂CO₃, and DMPU. The resulting chiral sulfinimidate esters are transformed to chiral sulfimides by the nucleophilic addition of the Grignard reagents under simple conditions. This transformation enables access to the enantioenriched diaryl or dialkyl sulfimides bearing two similar carbon substituents, which are difficult to synthesize by previous methods.     

Phase transition and conductive acceleration of phosphonium-cation-based room-temperature ionic liquid

An unusual ionic conduction phenomenon related to the phase transition of a novel phosphonium-cation-based room-temperature ionic liquid (RTIL) is reported; we found that in the phase change upon cooling, a clear increase in ionic conductivity was seen as the temperature was lowered, which differs from widely known conventional RTILs; clearly, our finding of abnormality of the correlation between temperature change and ionic conduction is the first observation in the electrolyte field.