Smiles rearrangement for the synthesis of 5-amino-substituted [1]benzothieno[2,3-b]pyridine

The Smiles rearrangement was successfully applied to 4-hydroxybenzo[b]thiophene furnishing a facile entry to the 4-amino derivative. The rearrangement was extended to 5-methoxy-4-methoxycarbonyl[1]benzothieno[2,3-b]pyridine obtained via aza-Wittig/electrocyclization reaction of novel N-(4-methoxybenzothiophen-2-yl)iminomethyldiphenylphosphorane with methyl trans-4-oxo-2-pentenoate. The preparation of a novel 5-amino-4-methoxycarbonyl[1]benzothieno[2,3-b]pyridine, which is of interest as a potential secondary peptide structure mimic, was successfully achieved.     

Kinetics of the Reaction of Abstracting Hydrogen from Ethylene by Hydrogen Atom

Hydrogen abstraction reaction, H C2H4 --H2 C2H2 was studied by using A initio SCF method. Ge-ometries were fully optimized at SCF level and energies were computed at STO-3G basis set for reactants and transition state. Vibrational analysis was performed thereupon. Finally, the rate constant calculations were carried out at different temperatures for all range of reaction temperature according to Eyring's sbwlute reaction rate theory. The calculated activation energy is 12. 68 kcal/mol, lower than observed value (H. S kcal/mol) by 1. 82 kcal/mol only. The agreement of the calculated rate constants with the experiments is satisfactory.     

Mechanism of Cp<Subscript>2</Subscript>ZrCl<Subscript>2</Subscript>-catalyzed olefin hydroalumination by alkylalanes

The composition of intermediates of the Cp₂ZrCl₂-catalyzed hydroalumination of α-olefins by isobutylalanes (HAlBuⁱ ₂, AlBuⁱ ₃, ClAlBuⁱ ₂) was studied by dynamic ¹H and ¹³C NMR pectroscopy. The reaction of Cp₂ZrCl₂ with isobutylalanes affords the complex (Cp₂ZrHCl·HAlBuⁱ ₂)₂ responsible for α-olefin hydroalumination.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 311–322, February, 2005.     

Michael-Addition Reaction of Malononitrile with α,β-Unsaturated Cycloketones Catalyzed by KF／Al2O3

A series of KF/Al2O3 catalyzed Michael-addition reactions between malononitrile and α,β-unsaturated cycloketones in DMF solution were studied. At room temperature, 2-cyano-3-aryl-3-(1,2,3,4-tetrahydronaphthalen-1-one-2-yl) propionitrile derivatives were synthesized by the reaction between 2-arylmethylidene-1,2,3,4-tetra-hydronaphthalen-1-one and malononitrile. However, if the temperature was increased to 80℃, 2-amino-3-cyano-4-aryl-4H-benzo[h]chromene derivatives were obtained in high yields. When the α,β-unsaturated ketones were replaced by 2,6-biarylmethylidenecyclohexanone or 2,5-biarylmethylidenecyclopentanone, another series of 2-amino-3-cyano-4H-pyran derivatives was isolated successfully. The structures of the products were confirmed by X-ray diffraction analysis.     

A comparative study on the photochemistry of two bipyridyl derivatives: [2,2'-bipyridyl]-3,3'-diamine and [2,2'-bipyridyl]-3,3'-diol.

The two isoelectronic bipyridyl derivatives, [2,2'-bipyridyl]-3,3'-diamine and [2,2'-bipyridyl]-3,3'-diol, are experimentally known to undergo very different excited-state double-proton-transfer processes, which result in fluorescence quantum yields that differ by four orders of magnitude. Herein, density functional theory (DFT), time-dependent DFT (TDDFT), and complete active space self-consistent field (CASSCF) calculations are used to study the double-proton-transfer processes in the ground and first singlet pi-->pi* excited state. The quantum-chemistry calculations indicate 1) the existence of only one energy minimum in the ground electronic state corresponding to reactants (thus avoiding the possibility of a fast fluorescent relaxation process from the photoproducts region), 2) an endoergic process of the complete double proton transfer, and 3) the presence of a conical intersection in the excited intermediate region of [2,2'-bipyridyl]-3,3'-diamine. These facts explain the very low fluorescence quantum yield in [2,2'-bipyridyl]-3,3'-diamine compared to [2,2'-bipyridyl]-3,3'-diol.     

Condensation reaction of 3-(methacryloxypropyl)-trimethoxysilane and diisobutylsilanediol in non-hydrolytic sol-gel process

The condensation reaction of 3-methacryloxypropyl-trimethoxysilane (MPTS) and diisobutylsilanediol (DIBSD) in a non-hydrolytic sol-gel process was investigated in terms of the reaction time and the catalyst amount for fabrication of inorganic-organic hybrid materials. The degree of condensation, which was characterized by ²⁹Si NMR, ¹H NMR and Abbe refractometry, increases with increased the reaction time and greater catalyst amount. However, a the large catalyst amount breaks the methacryl group during the condensation reaction. Thus, the reaction time and the catalyst amount were optimized to synthesize the condensed methacryl oligosiloxanes.     

Crystal structure of Mg0.65Sc0.35Dx deuterides studied by X-ray and neutron powder diffraction

The structural properties of the Mg_0.65Sc_0.35D_x deuterides have been investigated by X-ray and neutron powder diffraction at different deuterium content (0?x?2.2 D/f.u.). The metallic phase adopts a pseudo-CsCl structure (Pm-3m space group (SG); a=3.5921(2) Å) that transforms upon hydrogenation into a face centered cubic (FCC) phase involving an elongation of the c-axis, a shrinkage of the a-axis and a re-ordering of the metallic atoms. The fully hydrided compound (2.2 D/f.u.) adopts a cubic structure (Fm-3m SG; a=4.8087(7) Å) and deuterium is located in fully occupied tetrahedral sites and partially filled (24%) octahedral sites. Upon desorption, a two-phase domain appears with coexistence of a hydrogen-rich (1.55 D/f.u.) and a hydrogen-poor (0.85 D/f.u.) phase (Fm-3m SG; a=4.7598(3) and 4.6936(3) Å, respectively). All deuterium atoms are located in the tetrahedral sites with different occupancy factors: 77% for the H-rich phase and 43% for the H-poor phase. The appearance of a plateau in the pressure-composition-isotherm curve measured at 573 K confirms this two-phase behavior. The structural properties of the Mg_0.65Sc_0.35D_x system are discussed and compared with other body centered cubic (BCC) alloys adopting the same structure.     

Synthesis of β-amino carbonyl compounds via a Zn(OTf)2-catalyzed cascade reaction of anilines with aromatic aldehydes and carbonyl compounds

A Zn(OTf)₂-catalyzed cascade reaction of anilines with aromatic aldehydes and carbonyl compounds was described. This one-pot three-component reaction afforded the corresponding β-amino carbonyl compounds, β-amino esters, and β-amino ketones in good to excellent yields. The reaction was also applied for the liquid-phase synthesis of β-amino carbonyl compound library using PEG as a support.     

Ab initio study on the mechanism of reaction HNCO+NH2

Ab initio UMP2 and UQCISD(T) calculations, with 6-311G** basis sets, were performed for the titled reactions. The results show that the reactions have two product channels: NH₂+ HNCO?NH₃+NCO (1) and NH₂+HNCO?N₂H₃+CO (2), where reaction (1) is a hydrogen abstraction reaction via an H-bonded complex (HBC), lowering the energy by 32.48 kJ/mol relative to reactants. The calculated QCISD(T)//MP2(full) energy barrier is 29.04 kJ/mol, which is in excellent accordance with the experimental value of 29.09 kJ/mol. In the range of reaction temperature 2300–2700 K, transition theory rate constant for reaction (1) is 1.68×10¹¹–3.29×10¹¹ mL·mol^-1·s^-1, which is close to the experimental one of 5.0×10¹¹mL·mol^-1·s^-1or less. However, reaction (2) is a stepwise reaction proceeding via two orientation modes,cis andtrans, and the energy barriers for the rate-control step at our best calculations are 92.79 kJ/mol (forcis-mode) and 147.43 kJ/mol (fortrans-mode), respectively, which is much higher than reaction (1). So reaction (1) is the main channel for the titled reaction.     

H2 + CN(n=0,1)→H + HCN振动选态反应

用从头算方法获得了Ｈ２＋ＣＮ反应的内禀反应坐标（ＩＲＣ），沿着ＩＲＣ，计算了各垂直于ＩＲＣ的简正模所对应的频率（Ｗ）以及沿ＩＲＣ运动与垂直ＩＲＣ运动的简正模之间的耦合常数（ＢＫＦ），根据传统过渡态，变分过渡态理论和选态公式，计算了ｎＣＮ＝０及ｎＣＮ＝１时反应的速率常数，并得到了实验相一致的结果，还计算了ｎＣＨ＝１及ｎＣＮ＝１的Ｈ＋ＨＣＮ→Ｈ２＋ＣＮ反应速率常数，可供实验工作者参考。