Synthesis of Chiral Pyridylphenols for the Enantioselective Addition of Diethylzinc to Aldehydes

Chiral 8‐substituted 2‐(8,10,10‐trimethyl‐6‐aza‐tricyclo[7.1.1.0^2,7]undeca‐2(7),3,5‐trien‐5‐yl)‐phenols were prepared from a high enantiopurity (>97% ee) of (1R)‐(+)‐α‐pinene, and assessed in the enantioselective addition of diethylzinc to substituted benzaldehydes, giving the (S)‐alcohols with enantiomeric excess ranging from 33% to 89%. Interestingly, in all cases, except for those of ortho‐chlorobenzaldehyde, ortho‐ and para‐methoxybenzaldehydes, the ee was >71%. The plot of the Hammett substitution constants vs. enantiomeric excess of the diethylzinc addition to either the ortho‐ or para‐substituted benzaldehydes shows a linear correlation.     

Effect of delay on a predator–prey model with parasitic infection

In the paper an eco-epidemic system with delay and parasitic infection in the prey is investigated. The conditions for asymptotic stability of steady states are derived and the length of the delay preserving the stability is also estimated. Further, the criterion for existence of Hopf-type small amplitude periodic oscillations of the predator and prey biomass is derived. Numerical results indicate that the delay does not affect the stability of the system in the process but makes all populations oscillate more intensively. In addition, the results show that the recovery makes the levels of the infected prey and the predator become lower but makes the sound prey higher in limit time.     

Synthesis and biological evaluation of hydrazone and pyrazoline derivatives derived from androstenedione

Research on Chemical Intermediates - Here, two series of 17-hydrazone derivatives and D-fused pyrazoline derivatives possessing various aromatic heterocycle structures from androstenedione were...     

Gamma irradiation effect on chain segment motion and charge detrapping in polyamide 610

Gamma irradiation effect on the chain segment motion and charge detrapping in polyamide 610 was investigated by means of thermally stimulated depolarization current (TSDC), wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC) and gel fraction. There are four current peaks (named α, ρ₁, ρ₂ and ρ₃ peak, respectively) in TSDC spectra of polyamide 610. The α peak corresponds to the glass transition, the ρ₁ peak is attributed to space charge trapped in the amorphous phase, the ρ₂ peak is originated from space charge trapped in the interphase between crystalline and amorphous regions and the ρ₃ peak is originated from space charge trapped in crystalline phase. With the increase of irradiation dose from 1.5 to 2 MGy, ρ₁ and ρ₂ peaks gradually merge into one single peak. With the increase of irradiation dose the degree of crosslinking in amorphous phase is more than that in interphase and then the trap depth of interphase is gradually close to that of amorphous phase. By analyzing the characteristic parameters of these peaks, it is found that gamma irradiation can reduce the mobility of chain segments and increase structural defects in polyamide 610. In addition, irradiation increases the stability of trapped charge in both amorphous phase and interphase, but not affecting the stability of trapped charge in crystalline phase.     

Dinaphthobenzo[1,2:4,5]dicyclobutadiene: Antiaromatic and Orthogonally Tunable Electronics and Packing

Polycyclic conjugated hydrocarbons containing antiaromatic four‐membered cyclobutadienoids (CDB) are of great fundamental and technical interest. However, their challenging synthesis has hampered the exploration and understanding of such systems. Reported herein is a modular and efficient synthesis of novel CBD‐containing acene analogues, dinaphthobenzo[1,2:4,5]dicyclobutadiene (DNBDCs), with orthogonally tunable electronic properties and molecular packing. The design also features strong antiaromaticity of the CBD units, as revealed by nucleus‐independent chemical shift and anisotropy of the induced current density calculations, as well as X‐ray crystallography. Tuning the size of silyl substituents resulted in the most favorable “brick‐layer” packing for triisobutylsilyl‐DNBDC and a charge mobility of up to 0.52 cm² V^?1 s^?1 in field‐effect transistors.     

The second order hyperpolarizability of cis azobenzene isomer

The second order hyperpolarizability of cis azobenzene isomer (γ_c) was obtained by measuring the third harmonic generation (THG) variation of an azobenzene doped polymer film when the film was optically pumped to create a large amount of cis isomers via photoisomerization. A steady state theory was developed to treat the THG intensity variation by considering the optical pump induced redistribution and reorientation of azobenzene in the polymer film and the contribution of cis isomer to the THG signal. The ratio of γ of cis and trans molecule, (γ_c/γ_t), was found to be 0.51. After the γ_t was obtained from the time-resolved optical Kerr effect (OKE) measurement, γ_c was deduced to be 5.6 × 10⁻³³ esu. The result shows that the optical nonlinearity of cis isomer is clearly not negligible.