【作者】 徐红霞；

【导师】 佟振合； 吴骊珠； 张丽萍；

【作者基本信息】 中国科学院研究生院（理化技术研究所） ， 有机化学， 2009， 博士

【摘要】 控制光化学反应的立体选择性是一项具有挑战性的课题。2-萘甲酸烷基酯光化学二聚生成四种类立方烷结构的二聚体,其中的三种二聚体具有手性,并具有刚性骨架,有可能用于超分子组装和不对称催化。本论文利用手性辅助剂战略和手性微反应器战略,成功的提高了类立方烷二聚体的立体选择性。1、手性辅助剂控制的2-萘甲酸烷基酯光二聚反应的立体选择性:合成了9个带有手性辅助剂的2-萘甲酸烷基酯,研究了它们在有机溶剂中的光二聚反应。发现它们生成四种类立方烷二聚体:anti^HH,syn^HH,anti^HT和syn^HT。手性辅助剂对anti^HH, anti^HT和syn^HT的生成具有显著的不对称诱导作用,anti^HH的非对映异构体过量（d.e.）值高达近60%。2、手性辅助剂和手性微反应器（γ-环糊精）共同控制的2-萘甲酸烷基酯光二聚反应的立体选择性:成功地利用手性辅助剂和手性微反应器（γ-环糊精）相结合的方法控制了2-萘甲酸烷基酯光二聚反应的区域选择性和立体选择性。底物和γ-环糊精的包结物在固相中可以发生光二聚反应,生成的anti^HH二聚体的d.e.值高达94%,syn^HT的d.e.值高达88%,是迄今为止报道的环糊精诱导光化学反应立体选择性的最好结果。与溶液中进行的光二聚反应相比,在γ-环糊精固体包结物中生成的主要二聚体antiHH的立体选择性发生反转,该类现象未见文献报道。更多还原

【Abstract】 Enantioselectivity in organic phototransformations continues to be one of the main topics of current interest. Of the various approaches chiral auxiliary strategy and chiral microreactor strategy have shown considerable promise. In the former strategy a removable chiral auxiliary is connected to the prochiral starting substrate by a covalent bond. The chiral auxiliary in this case can bring about asymmetric induction during the photochemical transformation, resulting in diastereomers. The yielding diastereomers can be easily separated even in the case of low asymmetric induction. After the removal of the chiral auxiliary, the enantiomerically pure products can be obtained. In the chiral microreactor strategy inherently chiral hosts or chirally modified confined media are used as microreactors that provide cavities and/or surfaces to accommodate the prochiral substrate molecules and direct the photochemical reaction to proceed in an enantioselective manner. Among the various chiral microreactors thus far explored cyclodextrins （CDs） are most extensively investigated.Previously our group investigated the photodimerization of alkyl 2-naphthoates. Irradiation of these substrates results in four cubane-like phtodimers: head-to-head （HH） or head-to-tail （HT） isomers with syn and anti isomerism, denoted as anti^HH, anti^HT, syn^HT and syn^HH. The former three photodimers each consist of a pair of enantiomers. Our interest in the chirality of these photodimers originate from the fact that the cubane-like skeleton of these photodimers is strained and rigid. Thus, the derivatives of these photodimers might act as chiral ligands, and show applications in asymmetric catalysis and in molecular assemblies. In this thesis we made use of chiral auxiliary strategy and chiral microreactor strategy to achieve asymmetric induction in the photodimerizaiton of 9 alkyl 2-naphthoates with chiral auxiliaries. We are pleased to note that excellent chiral induction in the formation of anti^HH and syn^HT photodimers was obtained.1. Diastereodifferentiating photodimerization of alkyl 2-naphthoates with chiral auxiliaries: We synthesized 9 alkyl 2-naphthoates with different chiral auxiliaries. Irradiation of these 2-naphthoates in organic solution produced four photodimers: anti^HH, anti^HT, syn^HT and syn^HH. Diastereomeric excesses close to 60% were achieved in the formation of anti^HH photodimer.2. Switch and enhancement of diastereoselectivity in the photodimerization of alkyl 2-naphthoates via complexation withγ-cyclodextrin: Irradiation of alkyl 2-naphthoates with chiral auxiliaries included inγ-cyclodextrin in solid state resulted in anti^HH, anti^HT and syn^HT photodimers. Diastereomeric excesses of 94% and 88% in the formation of anti^HH and syn^HT photodimers were obtained respectively. The chirality of anti^HH photodimer is switched in comparison with that of solution photodimerization. As far as we are aware, this is the first example of the switching of product chirality and the best result of chiral induction for photochemical reactions with cyclodextrins as chiral host.更多还原