TY - JOUR
T1 - Supramolecular catalysis of the enantiodifferentiating [4 + 4] photocyclodimerization of 2-anthracenecarboxylate by γ-cyclodextrin
AU - Nakamura, Asao
AU - Inoue, Yoshihisa
PY - 2003/1/29
Y1 - 2003/1/29
N2 - 2-Anthracenecarboxylic acid (AC) makes a very stable 1:2 inclusion complex with γ-cyclodextrin (γ-CDx) (K1 = 161 ± 25 M-1, K2 = 38 500 ± 3300 M-1 at 25 °C). The formation of the 1:2 inclusion complex accelerated the photocyclodimerization of AC. The 1:2 inclusion could be clearly verified by UV-vis, CD, and 1H NMR spectroscopies. Although these spectroscopies provide little information about the structural isomers of the inclusion complex, there should be several structural isomers of the 1:2 inclusion complex which have a different longitudinal orientation of the guest molecules in the cavity. The isomer distribution of the photodimerization product primarily depends on the population of these orientational isomers of the 1:2 inclusion complex in the ground state before photoreaction, because, in the lifetime of the excited singlet state, exchanging the orientation is impossible. The enantioselectivity of the photodimerization originates from the difference in the stability of the diastereomeric pair of orientational isomers of the 1:2 inclusion complex in the ground state, which are the precursors of the enantiomers of a specific chiral cyclodimer. The ee of a chiral cyclodimer 2 was 32% at 25 °C and was enhanced by lowering the temperature to 41% at 0 °C. This is the highest value reported for the asymmetric photodimerization in solution.
AB - 2-Anthracenecarboxylic acid (AC) makes a very stable 1:2 inclusion complex with γ-cyclodextrin (γ-CDx) (K1 = 161 ± 25 M-1, K2 = 38 500 ± 3300 M-1 at 25 °C). The formation of the 1:2 inclusion complex accelerated the photocyclodimerization of AC. The 1:2 inclusion could be clearly verified by UV-vis, CD, and 1H NMR spectroscopies. Although these spectroscopies provide little information about the structural isomers of the inclusion complex, there should be several structural isomers of the 1:2 inclusion complex which have a different longitudinal orientation of the guest molecules in the cavity. The isomer distribution of the photodimerization product primarily depends on the population of these orientational isomers of the 1:2 inclusion complex in the ground state before photoreaction, because, in the lifetime of the excited singlet state, exchanging the orientation is impossible. The enantioselectivity of the photodimerization originates from the difference in the stability of the diastereomeric pair of orientational isomers of the 1:2 inclusion complex in the ground state, which are the precursors of the enantiomers of a specific chiral cyclodimer. The ee of a chiral cyclodimer 2 was 32% at 25 °C and was enhanced by lowering the temperature to 41% at 0 °C. This is the highest value reported for the asymmetric photodimerization in solution.
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U2 - 10.1021/ja016238k
DO - 10.1021/ja016238k
M3 - Article
C2 - 12537495
AN - SCOPUS:0037471664
VL - 125
SP - 966
EP - 972
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
SN - 0002-7863
IS - 4
ER -