ORGANIC
LETTERS
2005
Vol. 7, No. 6
1007-1010
Trifluoromethyl Groups in Crystal
Design of 1,4-Diphenyl-1,3-butadienes
for Topochemical [2
Photodimerization
+ 2]
Jin Liu,* Natalie L. Wendt, and Kelly J. Boarman
Department of Chemistry, Murray State UniVersity, Murray, Kentucky 42071
Received December 3, 2004
ABSTRACT
UV irradiation of the powdered crystalline sample of each of three (E,E)-1,4-di(trifluoromethyl-substituted)phenyl-1,3-butadienes (1
found to yield a single [2 2] cycloaddition product in the solid state. Moreover, upon irradiation, the crystalline samples of two (E,E)-1,4-
di(trifluoromethyl- and fluorine-substituted)phenyl-1,3-butadienes (4, 5) undergo a similar conversion to afford a [2 2] cycloaddition product,
respectively. Our observations suggest that trifluoromethyl groups can be used to direct 1,4-diphenyl-1,3-butadiene molecules to form a
parallel, offset-stacked orientation suitable for topochemical [2 2] cycloaddition.
−3) was
+
+
+
Noncovalent π stacking interactions play an important role
in many areas of chemistry, biology, and material science.1
In particular, noncovalent π stacking interactions formed by
fluorine atoms are extremely versatile. Studies of π stacking
interactions between phenyl and perfluorophenyl rings2 or
between two perfluorophenyl rings3 have been reported in
the literature. Although the face-to-face stacking interactions
have been successfully used to construct an ideal architecture
for [2 + 2] photodimerization or photopolymerization,4 a
few studies were focused on stacking arrangements influ-
enced by trifluoromethyl groups.5 Our recent study has
indicated that the self-assembling of (E,E)-1,4-di(o-trifluoro-
methyl)phenyl-1,3-butadiene, (E,E)-1,4-di(m-trifluorometh-
yl)phenyl-1,3-butadiene, and (E,E)-1,4-di(p-trifluoromethyl)-
phenyl-1,3-butadiene is suitable for topochemical [2 + 2]
photodimerization in the solid state.6 Therefore, it has
occurred to us that trifluoromethyl groups could be used as
directing groups in crystal engineering of (E,E)-1,4-diphenyl-
1,3-butadienes (DPB).7 To further explore the scope of
trifluoromethyl groups as the new directing groups,8 it will
be interesting to know the effects of the number of trifluoro-
methyl groups attached to each phenyl ring on the formation
of the parallel, offset-stacked orientation of DPBs. Also,
questions regarding the compatibility of a trifluoromethyl
group with a fluorine atom as substituents in the self-
assembling of substituted DPBs need to be addressed. Herein,
we report our recent study of topochemical [2 + 2]
photodimerization of six trifluoromethyl-substituted DPBs.
(1) (a) Hunter, C. A. Angew. Chem., Int. Ed. Engl. 1993, 32, 1584-
1586. (b) Meyer, E. A.; Castellano, R. K.; Diederich, F. Angew. Chem.,
Int. Ed. 2003, 42, 1210-1250.
(2) (a) Cozzi, F.; Siegel, J. S. Pure Appl. Chem. 1995, 67, 683-689. (b)
Cozzi, F.; Ponzini, F.; Annunziata, R.; Cinquini, M.; Siegel, J. S. Angew.
Chem., Int. Ed. Engl. 1995, 34, 1019-1020.
(3) (a) Liu, J.; Murray, E. M.; Young, V. G., Jr. Chem. Commun. 2003,
1904-1905. (b) Caronna, T.; Liantonio, R.; Logothetis, T. A.; Metrangolo,
P.; Pilati, T.; Resnati, G. J. Am. Chem. Soc. 2004, 126, 4500-4501.
(4) (a) Coates, G. W.; Dunn, A. R.; Henling, L. M.; Ziller, J. W.;
Lobkovsky, E. B.; Grubbs, R. H. J. Am. Chem. Soc. 1998, 120, 3641-
3649. (b) Vishnumurthy, K.; Row, T. N. G.; Venkatesan, K. Photochem.
Photobiol. Sci. 2002, 1, 427-430.
(5) (a) Hof, F.; Scofield, D. M.; Schweizer, W. B.; Diederich, F. Angew.
Chem., Int. Ed. 2004, 43, 5056-5059. (b) Rashkin, M. J.; Waters, M. L. J.
Am. Chem. Soc. 2002, 124, 1860-1861.
(6) Liu, J.; Boarman, K. J. Chem. Commun. 2005, 304-305.
(7) (a) Tanaka, K.; Toda, F. Chem. ReV. 2000, 100, 1025-1074. (b)
Ramamurthy, V.; Venkatesan, K. Chem. ReV. 1987, 87, 433-481.
(8) Matsumoto, A.; Tanaka, T.; Tsubouchi, T.; Tashiro, K.; Saragai, S.;
Nakamoto, S. J. Am. Chem. Soc. 2002, 124, 8891-8902.
10.1021/ol0475111 CCC: $30.25
© 2005 American Chemical Society
Published on Web 02/12/2005