6066
J. Am. Chem. Soc. 1997, 119, 6066-6071
Asymmetric Photocyclization of Diarylethene Derivatives
Tadatsugu Yamaguchi,† Kingo Uchida,‡ and Masahiro Irie*
Contribution from the Department of Chemistry and Biochemistry, Graduate School of
Engineering, Kyushu UniVersity, Higashi-ku, Fukuoka, 812, Japan
ReceiVed January 21, 1997X
Abstract: Diarylethene derivatives, which have an optically active l- or d-menthyl group at the 2-position of benzo-
[b]thiophene ring, were synthesized. Irradiation with 450 nm light in solution led to the formation of diastereomer
pairs of the closed-ring forms. The product ratio of the diastereomers was dependent on solvent polarity and
temperature. In slightly polar (or polarizable) solvents, such as THF and toluene, an asymmetric photocyclization
was observed. At -40 °C in toluene, a diastereomer excess as large as 86.6% was observed. The mechanism of the
asymmetric photocyclization is discussed.
Introduction
with two chiral units (chirochromism)11a and those incorporated
into chiral matrices, such as cholesteric liquid crystals11b,c or
chiral polymers.12
Diarylethenes with heterocyclic rings undergo cyclization/
ring-opening photochromic reactions. The photogenerated
closed-ring form has either S-S or R-R asymmetric structure.
Photochromic compounds characteristically exhibit two dif-
ferent chemical forms which are reversibly transformed form
one to the other upon irradiation with light of appropriate wave-
lengths.1 The instant image-forming property without process-
ing has led to consideration of their use in a rewritable direct
read-after-write medium.2 The inherent drawback of the pho-
tochromic memory is a lack of readout stability. Photochromic
reactions are, in general, induced in proportional to the number
of photons absorbed by the medium. Therefore, the photo-
chromic memory is destroyed after many readout operations.
To avoid such inconvenience, it is indispensable to develop
nondestructive readout methods.3 One of the approaches is to
introduce gated reactivity to the photochromic system.4-6
Another approach is to discriminate between the two isomers
using light which cannot induce the photochromic reactions.
Changes in the reflective index,7 infrared absorption,8 and optical
rotation9 (or circular dichroism) can be detected with light of
wavelengths longer than the electronic absorption bands.
The enantiomers can be separated with a chiral high-perfor-
mance liquid chromatography (HPLC) column (Daicel Chiralcel
OD). For example, the enantiomer pairs of closed-ring forms
of bis(2-methylbenzo[b]thiophen-3-yl)perfluorocyclopentene,
1,2-bis(2,4,5-trimethylthiophen-3-yl)perfluorocyclopentene, 1,2-
bis(2,4-dimethyl-5-(4-methoxy-benzyl)thiophen-3-yl)perfluoro-
cyclopentene, and 1-(1,2-dimethyl-3-indolyl)-2-(2-cyano-3,5-
dimethylthiophen-4-yl)-N-(cyanomethyl)maleimide were detec-
ted.13 When an optically active substituent such as a l- or
d-methyl group is introduced to the above compounds, a
diastereodifferentiating photocyclization is expected to occur
under suitable conditions.14,15 Martin et al.,15 for example,
reported such a diastereodifferentiation in the photosynthesis
Several photochromic compounds, which have chirooptical
properties and change the optical rotation by photoirradiation,
have been reported. Typical examples are highly substituted
stilbenes9 and fulgides10 with helical asymmetry. They undergo
photochromic reactions between the two forms with different
optical rotations. Other examples are photochromic compounds
† Interdisciplinary Graduate School of Engineering Sciences.
‡ Institute of Advanced Material Study.
X Abstract published in AdVance ACS Abstracts, June 15, 1997.
(1) Du¨rr, H.; Bouus-Laurent, H. Photochromism, Molecules and Systems;
Elsevier: Amsterdam, 1990.
(2) (a) Hirshberg, H. J. Am. Chem. Soc. 1965, 78, 2304. (b) Feringa, B.
L.; Jager, W. F.; De Lange, B. Tetrahedron 1993, 49, 8267. (c) Irie, M.
PhotoreactiVe Materials for Ultrahigh Density Optical Memory; Elsevier:
Amsterdam, 1994.
(3) (a) Tatezono, F.; Harada, T.; Shimizu, Y.; Ohara, M.; Irie, M. Jpn.
J. Appl. Phys. 1993, 32, 3987. (b) Tsujioka, T.; Kume, M.; Irie, M. Jpn.
J. Appl. Phys. 1995, 34, 6439.
(10) (a) Yokoyama, Y.; Shimizu, Y.; Uchida, S.; Yokoyama, Y. J. Chem.
Soc., Chem. Commun. 1995, 785. (b) Yokoyama, Y.; Uchida, S.;
Yokoyama, Y.; Sugawara, Y.; Kurita, Y. J. Am. Chem. Soc. 1996, 118,
3100.
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Uchida, M.; Kume, M.; Irie, M. Bull. Chem. Soc. Jpn. 1996, 69, 1023.
(5) (a) Irie, M.; Miyatake, O.; Uchida, K. J. Am. Chem. Soc. 1992, 114,
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(6) (a) Yokoyama, Y.; Kurita, K. Nippon Kagaku Kaishi 1992, 998. (b)
Matsui, Y.; Taniguchi, H.; Yokoyama, Y.; Sugiyama, K.; Kurita, Y. Chem.
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(7) Tanio, N.; Irie, M. J. J. Appl. Phys. 1994, 33, 1550.
(8) Seibold, M.; Port, H. Chem. Phys. Lett. 1996, 252, 135.
(9) (a) Feringa, B. L.; Jager, W. F.; de Lange, B. J. Am. Chem. Soc.
1991, 113, 5458. (b) Feringa, B. L.; Jager, W. F.; de Lange, B. J. Chem.
Soc., Chem. Commun. 1993, 288.
(11) (a) Zhang, M.; Schuster, G. B. J. Am. Chem. Soc. 1994, 116, 4853.
(b) Zhang, M.; Schuster, G. B. J. Phys. Chem. 1992, 96, 3063. (c) Janicki,
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(12) Sisido, M.; Ishikawa, Y.; Ito, K.; Tazuke, S. Macromolecules 1991,
24, 3993.
(13) Enantiomer pairs of closed-ring forms of the following diarylethenes
were separated with a chiral column (Daicel Chiralcel OD): 1,2-bis-
(methylbenzo[b]thiophen-3-yl)perfluorocyclopentene (eluent, hexane), 1,2-
bis(2,4,5-trimethylthiophen-3-yl)perfluorocyclopentene (eluent, hexane), 1,2-
bis(2,4-dimethyl-5-(4-methoxybenzyl)thiophen-3-yl)-perfluoro-
cyclopentene (eluent, hexane/ethanol 99.4:0.6), and 1-(1,2-dimethyl-3-
indolyl)-2-(2-cyano-3,5-dimethylthiophen-4-yl)-N-(cyanomethyl)maleim-
ide (eluent, hexane/ethanol 4:1).
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