A series of optically active amidine dimers composed of m-terphenyl backbones joined by a variety of linkers, such as achiral and chiral p-phenylene and chiral amide linkers, were synthesized and used as templates for the regio- (head-to-tail (HT) or head-to-head (HH)), diastereo- (anti or syn), and enantioselective [4 + 4] photocyclodimerization of an achiral m-terphenyl-based carboxylic acid monomer bearing a prochiral 2-substituted anthracene at one end (1) through complementary amidinium–carboxylate salt bridges. The amidine dimers linked by p-phenylene linkages almost exclusively afforded the chiral syn-HT and anti-HH dimers at 25 °C, while those joined by amide linkers produced all four dimers. The p-phenylene-linked templates tended to enhance the syn-HT-photodimer formation at high temperatures with no significant changes in the product enantiomeric excess (ee), while the anti-HH-photodimer formation remarkably increased with the decreasing temperature accompanied by a significant enhancement of the product ee up to −86% at −50 °C. Temperature-dependent inversion of the chirality of the anti-HH dimer was observed when the chiral phenylene-linked amidine dimer was used and the product ee was changed from 22% at 50 °C to −86% at −50 °C. A similar enhancement of the enantioselectivity of the anti-HH dimer was also observed for the chiral amide-linked template, producing the anti-HH dimer with up to −88% ee at −50 °C. The observed difference in the regio-, diastereo-, and enantioselectivities due to the difference in the linker structures of the amidine dimers during the template-directed photodimerization of 1 was discussed on the basis of a reversible conformational change in the amidine dimers complexed with 1.

中文翻译：

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手性模板指导的蒽衍生物-Am盐-羧酸盐桥形成辅助的蒽衍生物的对位，非对映和对映选择性光二聚化

一系列组成的光学活性脒二聚体米通过多种连接体，如非手性和手性的接合-三联苯骨架p亚苯基和手性酰胺连接体，合成和用作区域选择性（头对尾的模板（ HT）或头-头（HH）），diastereo-（反或顺式），和不对称[4 + 4]非手性的photocyclodimerization米基于三联苯羧酸单体在一端带有前手性2位取代的蒽（1）通过互补的idi-羧酸盐桥。通过对-亚苯基键连接的dim二聚体几乎专门提供了手性syn -HT和抗-HH二聚体在25°C，而那些由酰胺连接基连接的三聚体产生了所有四个二聚体。的p亚苯基连接的模板倾向于增强顺在高温下与产品中的对映体过量（ee）没有显著变化-HT-photodimer的形成，而反-HH-photodimer形成显着地与伴随有下降的温度升高在−50°C下，产品ee显着提高至−86％。当使用手性亚苯基连接的am二聚体并且产物ee从50℃下的22％变为-50℃下的-86％时，观察到了抗-HH二聚体的手性的温度依赖性反转。对的对映选择性的类似提高抗在手性酰胺连接的模板上也观察到-HH二聚体，在-50°C下产生的抗-HH二聚体的ee最高为-88％。基于与1络合的am二聚体的可逆构象变化，讨论了在1的模板定向光二聚化过程中，由于the二聚体的接头结构不同而导致的区域选择性，对映体选择性和对映选择性的差异。。