2,6-anthracenedicarboxylic acids to reveal the configurational and molecular orbital origin of the Cotton effects observed, and unambiguously determined the absoluteconfigurations of these chiral cyclodimers. The present results allow us to directly correlate the enantiotopic face-selectivity upon photocyclodimerization with the absoluteconfiguration of the cyclodimer derived therefrom and also to
Cap in hand: Combined use of diamino‐γ‐cyclodextrin (CD) and Cu(ClO4)2 resulted in the first catalytic supramolecularphotochirogenesis in the photocyclodimerization of 2‐anthracenecarboxylic acid. The anti‐head‐to‐head cyclodimer formed in 64–70 % enantiomeric excess and about 50 % yield; these values are the highest ever reported for CD‐mediated photochirogenesis.
found to stepwise form 1:1 and 1:2 complexes, having a large K 1 and a relatively small K 2 values. Photocyclodimerization of AC within the pillar[6]arene improved the yield of the head-to-head photodimers. Up to 4.97 HH/HT ratio has been reached by optimizing the reaction conditions.
摘要通过1 H NMR,UV-vis和ITC方法研究了蒽羧酸与水溶性阳离子柱芳烃的络合行为。发现阳离子柱[6]芳烃逐步形成1:1和1:2的配合物,具有较大的K 1和相对较小的K 2值。柱[6]芳烃中AC的光环二聚化提高了头对头光二聚体的收率。通过优化反应条件,最高可达到4.97 HH / HT比率。
Chiral ionic liquid-mediated photochirogenesis. Enantiodifferentiating photocyclodimerization of 2-anthracenecarboxylic acid
Enantiodifferentiatingphotocyclodimerization 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%
Stereochemistry of the major photocyclodimer is switched from 52% anti-head-to-head to 51% anti-head-to-tail among the four stereoisomers produced upon irradiation of 2-anthracenecarboxylic acid at low temperatures by changing the solvent from dichloromethane to methanol, through a critical control of the hydrogen bonding and dipole–dipole interactions.