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Tanabe J, Taura D, Ousaka N, et al. Chiral Template-Directed Regio-, Diastereo-, and Enantioselective Photodimerization of an Anthracene Derivative Assisted by Complementary Amidinium-Carboxylate Salt Bridge Formation. J Am Chem Soc. 2017;139(21):7388-7398doi: 10.1021/jacs.7b03317.
Tanabe, J., Taura, D., Ousaka, N., & Yashima, E. (2017). Chiral Template-Directed Regio-, Diastereo-, and Enantioselective Photodimerization of an Anthracene Derivative Assisted by Complementary Amidinium-Carboxylate Salt Bridge Formation. Journal of the American Chemical Society, 139(21), 7388-7398. https://doi.org/10.1021/jacs.7b03317
Tanabe, Junki, et al. "Chiral Template-Directed Regio-, Diastereo-, and Enantioselective Photodimerization of an Anthracene Derivative Assisted by Complementary Amidinium-Carboxylate Salt Bridge Formation." Journal of the American Chemical Society vol. 139,21 (2017): 7388-7398. doi: https://doi.org/10.1021/jacs.7b03317
Tanabe J, Taura D, Ousaka N, Yashima E. Chiral Template-Directed Regio-, Diastereo-, and Enantioselective Photodimerization of an Anthracene Derivative Assisted by Complementary Amidinium-Carboxylate Salt Bridge Formation. J Am Chem Soc. 2017 May 31;139(21):7388-7398. doi: 10.1021/jacs.7b03317. Epub 2017 May 18. PMID: 28485968.
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J Am Chem Soc. 2017 May 31;139(21):7388-7398. doi: 10.1021/jacs.7b03317. Epub 2017 May 18.

Chiral Template-Directed Regio-, Diastereo-, and Enantioselective Photodimerization of an Anthracene Derivative Assisted by Complementary Amidinium-Carboxylate Salt Bridge Formation.

Journal of the American Chemical Society

Junki Tanabe, Daisuke Taura, Naoki Ousaka, Eiji Yashima

Affiliations

  1. Department of Molecular Design and Engineering, Graduate School of Engineering, Nagoya University , Chikusa-ku, Nagoya 464-8603, Japan.

PMID: 28485968 DOI: 10.1021/jacs.7b03317

Abstract

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.

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