Absolute asymmetric photocyclization of a photochromic diarylethene derivative in single crystals.
Absolute asymmetric photocyclization of a photochromic diarylethene derivative in single crystals.
复制标题
DOI：
10.1002/anie.200250417
复制
发表时间：
2003-04
影响因子：
--
通讯作者：
Satoshi Yamamoto;K. Matsuda;M. Irie
中科院分区：
文献类型：
--
作者：
Satoshi Yamamoto;K. Matsuda;M. Irie
近年来，晶体中化合物的光化学引起了相当大的科学兴趣。[1]主题广泛，从硅纳米晶体中的化学发光[2]到晶体中的化学反应。晶格为具有立体、区域和对映异构性的反应提供了基质。对映异构化反应可以发生在含有手性辅助剂的手性晶体中，例如手性主体分子[4]和共价键合的手性取代基。此外，在手性空间群中，通过反应可以将非手性分子系综转化为手性分子。这种在没有任何外界手性影响的情况下进行的不对称反应称为绝对不对称合成。绝对不对称合成的第一个例子是Penzien和Schmidt进行的气/固相反应。[6]光化学分子内反应中的绝对不对称合成是由Scheffer及其同事首次报道的。[7]1，4-二取代苯二丙烯酸酯衍生物的光化学绝对不对称合成[8]和4-[2-(4-吡啶)乙烯]肉桂酸乙酯的光化学绝对不对称合成[9]是拓扑化学反应的另一个典型例子。光致变色化合物的特征是表现出两种不同的化学形式，在适当波长的光照射下，从一种形式可逆地转变为另一种形式。虽然已经报道了许多光致变色化合物，但在晶相中发生反应的化合物相对较少。[10]一些二芳基乙烯衍生物甚至在单晶中也发生了热不可逆和耐疲劳的光致变色反应。光化学环化反应生成两个对映体闭环异构体(R，R和S，S)，其中手性起源于不对称碳原子(方案1)。通常，二芳基乙烯衍生物在溶液中的光环化反应导致两个对映体的生成。即使将手性取代基引入到二芳基乙烯中，也几乎不会发生其中一个非对映异构体的浓缩。[11]在光化学反应中，浓缩一个对映异构体或非对映异构体需要一个手性环境，就像通过络合到具有手性配体的铜(I)中心形成的手性环境，或者由手性取代基诱导的手性晶体堆积。[13]如果开放的异构体与手性堆积结晶，则绝对不对称光致变色，在没有任何外部手性物质的情况下，非手性化合物产生手性产物。
In recent years there has been considerable scientific interest in the photochemistry of compounds in crystals.[1] The topics range widely from chemiluminescence in silicon nanocrystals [2] to chemical reactivity in crystals.[3] One unique aspect of crystal-phase reactions is topochemical reactivity. The crystal lattice provides a matrix for reactions with stereo-, regio-, and enantiospecificity. Enantiospecific reactions can take place in chiral crystals containing chiral auxiliaries such as chiral host molecules [4] and covalently bonded chiral substituents.[5] Moreover, an ensemble of achiral molecules can be transformed by reactions into chiral molecules on crystallization in a chiral space group. Such an asymmetric reaction in the absence of any outside chiral influence is referred to as absolute asymmetric synthesis. The first example of absolute asymmetric synthesis, a gas/solid-phase reaction was carried out by Penzien and Schmidt.[6] Absolute asymmetric synthesis in a photochemical intramolecular reaction was first reported by Scheffer and coworkers.[7] The photochemical absolute asymmetric syntheses of 1, 4-disubstituted phenylenediacrylate derivatives [8] and ethyl 4-[2-(4-pyridyl) ethenyl] cinnamate [9] are other typical examples of topochemical reactions. Photochromic compounds characteristically exhibit two different chemical forms that are reversibly transformed from one to the other upon irradiation with light of appropriate wavelengths. Although numerous photochromic compounds have been reported, compounds that undergo reaction in the crystal phase are relatively rare.[10] Some diarylethene derivatives undergo thermally irreversible and fatigue-resistant photochromic reactions even in single crystals. The photochemical conrotatory cyclization produces two enantiomeric closed-ring isomers (R, R and S, S), in which the chirality originates from asymmetric carbon atoms (Scheme 1).The photocyclization of diarylethene derivatives in solution, in general, results in the formation of two enantiomers in equal amounts. Even when a chiral substituent is introduced into the diarylethene, enrichment of one of the diastereomers hardly takes place.[11] Enrichment of one of the enantiomers or diastereomers in photochemical reactions requires a chiral environment like that formed on complexation to a copper (i) center having chiral ligands [12] or chiral crystal packing induced by a chiral substituent.[13] If the open isomers would crystallize with chiral packing, absolute asymmetric photochromism, in which achiral compounds produce chiral products in the absence of any external chiral