title: Chiral ionic liquid-mediated photochirogenesis. Enantiodifferentiating photocyclodimerization of 2-anthracenecarboxylic acid.
abstract: Enantiodifferentiating photocyclodimerization of 2-anthracenecarboxylic acid (AC-H) and its lithium salt (AC-Li) in chiral ionic liquid (CIL), (R)-1-(2,3-dihydroxypropyl)-3-methylimidazolium acetate {[(R)-GLYMI][AcO]}, gave a mixture of two head-to-tail (HT) and two head-to-head (HH) cyclodimers in HT/HH ratios of 1.3-1.7 (for AC-H) and 2.2-4.3 (for AC-Li) with low enantiomeric excesses (ee) of 0-3% for chiral syn-HT and anti-HH dimers. In contrast, irradiation of AC-H in an aqueous solution, containing cucurbit[8]uril (CB[8]) as a host and [(R)-GLYMI][AcO] or [(R)-GLYMI][Tf(2)N] as a modifier of CB portals, afforded the HH dimers in 91-99% selectivity, although the anti-HH dimer was totally racemic. Interestingly, irradiation of AC-H in a dichloromethane solution, containing [(R)-GLYMI][AcO] as a chiral template, led to the formation of the HH-dimers in 98% selectivity with chiral anti-HH dimer in -14% ee, presumably by the dual ligation of two ACs to a CIL through electrostatic and hydrogen-bonding interactions.
authors: Department of Applied Chemistry, Osaka University, 2-1 Yamada-oka, Suita, 565-0871, Japan. gaku@chem.eng.osaka-u.ac.jp
authors: Gaku
authors: G
authors: Fukuhara
authors: Takahiro
authors: T
authors: Okazaki
authors: Marco
authors: M
authors: Lessi
authors: Masaki
authors: M
authors: Nishijima
authors: Cheng
authors: C
authors: Yang
authors: Tadashi
authors: T
authors: Mori
authors: Andrea
authors: A
authors: Mele
authors: Fabio
authors: F
authors: Bellina
authors: Cinzia
authors: C
authors: Chiappe
authors: Yoshihisa
authors: Y
authors: Inoue
mesh_terms: D000873:Anthracenes / Q000737:chemistry*; D002264:Carboxylic Acids / Q000737:chemistry*; D003500:Cyclization; D019281:Dimerization; D052578:Ionic Liquids / Q000737:chemistry*; D015394:Molecular Structure; D055668:Photochemical Processes; D012997:Solvents / Q000737:chemistry; D055672:Static Electricity; D013237:Stereoisomerism
chemical_list: D000873:Anthracenes; D002264:Carboxylic Acids; D052578:Ionic Liquids; D012997:Solvents; C107996:anthracene-1-carboxylic acid