随着国家扩大免疫规划工作的不断深入,接种覆盖人群不断扩大,使用疫苗的种类和数量不断增多,预防接种的安全性问题也日渐突出。疑似预防接种异常反应（adverse events following immunization,AEFI）日益受到关注[1]。AEFI是我国扩大免...随着国家扩大免疫规划工作的不断深入,接种覆盖人群不断扩大,使用疫苗的种类和数量不断增多,预防接种的安全性问题也日渐突出。疑似预防接种异常反应（adverse events following immunization,AEFI）日益受到关注[1]。AEFI是我国扩大免疫规划顺利实施的一个重要影响因素,及时发现、有效处置AEFI病例,是防止AEFI导致突发事件的关键[2]。开展AEFI监测,展开更多
The silver（1）-catalyzed synthesis picture of axially chiral allenes based on propargylamines has been outlined using density functional theory （DFT） method for the first time. Our calculations find that, the coord...The silver（1）-catalyzed synthesis picture of axially chiral allenes based on propargylamines has been outlined using density functional theory （DFT） method for the first time. Our calculations find that, the coordination of sil- ver（I） into triple bond of propargylamines at anti-position of nitrogen shows a stronger activation on the triple bond than that at cis-position, which is favorable for the subsequent hydrogen transfer. The NBO charge analysis for the hydrogen transfer affirms the experimental speculation that this step is a hydride transfer process. The energy bar- rier of the anti-periplanar elimination of vinyl-silver is 26.9 kJomol l lower than that of the syn-periplanar elimina- tion, supporting that （--）-allene is the main product of this reaction. In a word, the most possible route for this reac- tion is that the silver（I） coordinates into the triple bond of propargylamines at anti-position of nitrogen, then the formed silver（I） complex undergoes a hydride transfer to give a vinyl-silver, finally the vinyl-silver goes through an anti-periplanar elimination to give （--）-allene. The hydride transfer with the energy barrier of 44.8 kJ.mol-1 is the rate-limiting step in whole catalytic process. This work provides insight into why this reaction has a very high enan- tioselectivity.展开更多
文摘随着国家扩大免疫规划工作的不断深入,接种覆盖人群不断扩大,使用疫苗的种类和数量不断增多,预防接种的安全性问题也日渐突出。疑似预防接种异常反应（adverse events following immunization,AEFI）日益受到关注[1]。AEFI是我国扩大免疫规划顺利实施的一个重要影响因素,及时发现、有效处置AEFI病例,是防止AEFI导致突发事件的关键[2]。开展AEFI监测,
文摘The silver（1）-catalyzed synthesis picture of axially chiral allenes based on propargylamines has been outlined using density functional theory （DFT） method for the first time. Our calculations find that, the coordination of sil- ver（I） into triple bond of propargylamines at anti-position of nitrogen shows a stronger activation on the triple bond than that at cis-position, which is favorable for the subsequent hydrogen transfer. The NBO charge analysis for the hydrogen transfer affirms the experimental speculation that this step is a hydride transfer process. The energy bar- rier of the anti-periplanar elimination of vinyl-silver is 26.9 kJomol l lower than that of the syn-periplanar elimina- tion, supporting that （--）-allene is the main product of this reaction. In a word, the most possible route for this reac- tion is that the silver（I） coordinates into the triple bond of propargylamines at anti-position of nitrogen, then the formed silver（I） complex undergoes a hydride transfer to give a vinyl-silver, finally the vinyl-silver goes through an anti-periplanar elimination to give （--）-allene. The hydride transfer with the energy barrier of 44.8 kJ.mol-1 is the rate-limiting step in whole catalytic process. This work provides insight into why this reaction has a very high enan- tioselectivity.
