Regioselective rapid triazole syntheses at low temperature are described. Organic azides and propargyl cations generated by acids gave fully substituted 1H-1,2,3-triazoles. Most reactions could be performed in 5 min at not only rt but also -90 °C. Both terminal and internal alkynes were acceptable, and the sterically bulky substituents could afford the products smoothly. Various types of three-component coupling reactions were demonstrated, and the presence of allenylaminodiazonium intermediates was indicated.
Monte Carlo simulations of hot electron transport in AlGaAs/GaAs /AlGaAs quantum wells were carried out in order to clarify the drift velocity overshoot and steady state drift velocity versus the electric-field relation. In the simulations, we took into account the nonparabolic isotropic energy band structures. Results are given for GaAs well widths of 500 and 100 Å and an electron sheet density of 1.0×1012 cm-2 at 77 K. The drift-velocity overshoot reaches about 7×107 cm/s at an electric field of 10 kV/cm in both quantum well structures. A negative differential mobility appears beyond 3 kV/cm in both structures due to electron transfer from the Γ valley to the L valleys.
Organic azides have been exploited since their discovery because of their high reactivities. Various organic reactions using azides have been synthetically applied in chemical biology, pharmaceuticals, medicinal, and agricultural areas. In this review, we present some recent applications and developments of organic azides in the total synthesis of natural products (mostly within five years), especially alkaloids. We focus not only on application examples of organic azides, but also show their preparation methods including recently reported procedures concerning their decomposing and reducing methods in the syntheses of bioactive molecules.
A typical (Paterno-Buchi type) organic photoreaction is examined in flow microreactors. Compared to the results achieved for simple one-layer flow modes, slug flow conditions (with the unreactive reagent composed of organic solution and water) achieve higher efficiency (conversion and yield) irrespective of the light source, concentration, and solvent. Furthermore, remarkably high productivity is also observed when only 5% water is added as an unreactive reagent. This method is broadly applicable for achieving highly efficient organic photoreactions not only in the laboratory, but also on the industrial scale.
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