Synchronous enantiomeric enrichment of both reactant and product by absolute asymmetric synthesis using circularly polarized light. Part 3. Numerical simulation and experimental verification of the reversible asymmetric photoisomerization between methyl norbornadiene-2-carboxylate and methyl quadricyclane-1-carboxylate
作者:Hideo Nishino、Asao Nakamura、Hiroshi Shitomi、Hideo Onuki、Yoshihisa Inoue
DOI:10.1039/b100753j
日期:——
In the first paper of this series, we proposed a new absolute asymmetric synthesis (NAAS) with circularly polarized light (CPL), which can be classified into two subcategories: (a) reversible NAAS (CPL excites both the reactant and product), (b) irreversible NAAS (the reactant only is excited by CPL). In the present paper we deal with reversible NAAS. The numerical simulations, which are based upon the results of the preceding paper of this series, are performed. Using the reversible photoisomerization between methyl norbornadiene-2-carboxylate (I) and methyl quadricyclane-1-carboxylate (II), it was experimentally verified that the enantiomeric excesses (ee's) of both the reactant and product were critically dependant not only on the anisotropy factors (g = Δε/ε) of both components, but also on the relative quantum yields of the forward and reverse reactions. In the case of reversible NAAS, the ee of the reactant and the product will concurrently increase according to the conversion, and attain appreciable values at the photostationary state if we appropriately select the system and the CPL-irradiation wavelength in such a way that if the g factors of the product and the reactant are large enough, the sign of the g factor of the product is opposite to that of the reactant, and the photochemical equilibrium constant K is less than unity.
在本系列的第一篇论文中,我们提出了一种新的圆偏振光(CPL)绝对不对称合成(NAAS),它可以分为两个子类:(a)可逆NAAS(CPL同时激发反应物和产物),( b) 不可逆NAAS(反应物仅被CPL激发)。在本文中,我们讨论可逆 NAAS。数值模拟是基于本系列前一篇论文的结果进行的。利用降冰片二烯-2-甲酸甲酯(I)和四环烷-1-甲酸甲酯(II)之间的可逆光致异构化,实验验证了反应物和产物的对映体过量(ee's)不仅取决于各向异性两个组分的因子 (g = Δε/ε),而且还影响正向和反向反应的相对量子产率。在可逆NAAS的情况下,如果我们适当地选择系统和CPL照射波长,反应物和产物的ee将根据转化同时增加,并且在光稳态下获得可观的值产物和反应物的g因子足够大,产物的g因子的符号与反应物的g因子相反,并且光化学平衡常数K小于1。