title: Supramolecular Photochirogenesis with a Higher-Order Complex: Highly Accelerated Exclusively Head-to-Head Photocyclodimerization of 2-Anthracenecarboxylic Acid via 2:2 Complexation with Prolinol.
abstract: An unprecedented 2:2 complex was shown to intervene in the enantiodifferentiating photocyclodimerization of 2-anthracenecarboxylic acid (A) mediated by a hydrogen-bonding template l-prolinol (P) to accelerate the formation of chiral anti-head-to-head and achiral syn-head-to-head cyclodimers in >99% combined yield with enhanced enantioselectivities of up to 72% ee for the former. The supramolecular complexation and photochirogenic behaviors, as well as the plausible structures, of intervening Am·Pn complexes (m, n = 1 or 2) were elucidated by combined theoretical and experimental spectroscopic, photophysical, and photochemical studies. Furthermore, the photochemical chiral amplification was achieved for the first time by utilizing the preferential 2:2 complexation of A with homochiral P to give normalized product enantioselectivities higher than those of the template used. The present strategy based on the higher-order hydrogen-bonding motif, which is potentially applicable to a variety of carboxylic acids and β-aminoalcohols, is not only conceptually new and expandable to other (photo)chirogenic and sensing systems but also may serve as a versatile tool for achieving photochemical asymmetric amplification and constructing chiral functional supramolecular architectures.
authors: Yuko
authors: Y
authors: Kawanami
authors: Shin-Ya
authors: SY
authors: Katsumata
authors: Masaki
authors: M
authors: Nishijima
authors: Gaku
authors: G
authors: Fukuhara
authors: Comprehensive Analysis Center, Institute of Scientific and Industrial Research, Osaka University , Mihogaoka, Ibaraki 567-0047, Japan.
authors: Kaori
authors: K
authors: Asano
authors: Comprehensive Analysis Center, Institute of Scientific and Industrial Research, Osaka University , Mihogaoka, Ibaraki 567-0047, Japan.
authors: Takeyuki
authors: T
authors: Suzuki
authors: Key Laboratory of Green Chemistry & Technology (Ministry of Education), College of Chemistry, Sichuan University , Wangjiang Road, Chengdu 610064, China.
authors: Cheng
authors: C
authors: Yang
authors: Department of Chemistry, College of Engineering, Shibaura Institute of Technology , Saitama-shi 337-8570, Japan.
authors: Asao
authors: A
authors: Nakamura
authors: Tadashi
authors: T
authors: Mori
authors: Yoshihisa
authors: Y
authors: Inoue