X-ray crystallographic analysis of N,N-diallylcoumarincarboxamides and the solid-state photochemical reaction

Article abstract of DOI:10.1016/j.tet.2006.01.037

X-ray crystallographic analysis and the photochemical aspects of N,N-diallylcoumarincarboxamides were investigated. Irradiation of the corresponding amides promoted stereoselective intramolecular cyclobutane formation exclusively. The solid-state photoreaction of the coumarinamide without substituent on the 4-position proceeded in a crystal-to-crystal manner. On the other hand, photolysis of the amide possessing a methyl group at the 4-position also effected 2+2 cycloaddition; however, the reaction proceeded much slower. The difference in the reactivity was explainable on the basis of the molecular conformation in the crystal lattice.

Full text of DOI:10.1016/j.tet.2006.01.037

Tetrahedron 62 (2006) 3028–3032
X-ray crystallographic analysis of
N,N-diallylcoumarincarboxamides and the solid-state
photochemical reaction
*
Masami Sakamoto, Mamoru Kato, Eishi Oda, Shuichiro Kobaru,
Takashi Mino and Tsutomu Fujita
Department of Applied Chemistry and Biotechnology, Faculty of Engineering, Chiba University,
Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
Received 31 October 2005; revised 11 January 2006; accepted 12 January 2006
Available online 2 February 2006
Abstract—X-ray crystallographic analysis and the photochemical aspects of N,N-diallylcoumarincarboxamides were investigated.
Irradiation of the corresponding amides promoted stereoselective intramolecular cyclobutane formation exclusively. The solid-state
photoreaction of the coumarinamide without substituent on the 4-position proceeded in a crystal-to-crystal manner. On the other hand,
photolysis of the amide possessing a methyl group at the 4-position also effected 2C2 cycloaddition; however, the reaction proceeded much
slower. The difference in the reactivity was explainable on the basis of the molecular conformation in the crystal lattice.
q 2006 Elsevier Ltd. All rights reserved.
1. Introduction
have found that N,N-diallylcoumarin-3-caboxamides
showed effective photochemical reactivity and gave
cylobutanes selectively, and one of the reactions proceeded
in a crystal-to-crystal manner.
Solid-state photoreaction provides product- and stereo-
selectivity compared to reactions that occur in solution due
to restriction of molecular movement imposed by the
environment.1 Many examples are reported of topochemical
intermolecular 2C2 cyclobutane formation of alkenes, and
the geometrical studies are well-known as Schmidt’s rule,
which means that the reactive alkenyl groups locate within
2. Results and discussion
N,N-Diallylcoumarin-3-carboxamide 1a and the 4-methyl
derivative 1b were conveniently prepared from the
˚
4.2 A of the center-to-center distance in parallel to
promoted cycloaddition.2 Compared to a large amount of
data for intermolecular cycloaddition reactions,3 there is
little information on intramolecular reactions.4 Intermole-
cular reactions are strongly affected by the molecular
arrangement in the crystal; on the other hand, molecular
conformation in the ground-, excited- and transition-state
also plays an important role in the intramolecular
photoprocess. To investigate the geometrical aspects of
intramolecular 2C2 photocycloaddition and the difference
between photochemical reactivity with the reaction media,
photochemical reaction of N,N-diallylcoumarin-3-carbox-
amides was examined, because coumarin is well-known as
not only one of the photoreactive molecules for dimeri-
zation and 2C2 cycloaddition with alkenes,5 but also
natural products and biologically active materials.6 Now we
Table 1. Photochemical reaction of N,N-diallylcoumarincarboxamides 1
R
O
R
N
O
h n
N
O
O
O
O
1a: R = H
1b: R = Me
2a: R = H
2b: R = Me
Entry
Amide 1
Conditionsa
Conversion
(%)
Yield (%)
of 2b
1
2
3
4
5
1a
1a
1b
1b
1b
Benzene (5 h)c
Solid-state (2 h)
Benzene (12 h)c
Solid-state (6 h)
Solid-state (12 h)
100
100
47
46
99
98
100
50
100
74
a A 0.02 M benzene solution in a Pyrex vessel under argon was irradiated
with a 500 W high pressure mercury lamp.
Keywords: Coumarincarboxamide derivatives; Solid-state reaction; 2C2
Cycloaddition; X-ray crystallography; Photochemical reaction.
*
b Chemical yields were determined on the basis of consumed coumarins.
c Number in parentheses is irradiation time.
Corresponding author. Tel.: C81 43 290 3387; fax: C81 43 290 3401;
e-mail: sakamotom@faculty.chiba-u.jp
0040–4020/$ - see front matter q 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2006.01.037

M. Sakamoto et al. / Tetrahedron 62 (2006) 3028–3032
3029
corresponding carboxylic acids (Table 1).7 Recrystallization
of the amide 1a from a mixture of chloroform and hexane
gave colorless plates, and 1b afforded colorless needles.
Both amides were subjected to X-ray single crystal analysis,
and Figure 1 shows the ORTEP view of the amides 1a–b.
Each amide plane twisted almost orthogonally to the
coumarin chromophore, and the torsion resulted in closed
orientation of the reacting alkenyl bonds.
the X-ray powder diffraction as shown in Figure 3. Figure 3a
shows the spectrum of starting material 1a; Figure 3b
exhibited the reflection pattern of 100% conversion yield,
and still shows sharp reflections. Figure 3c, derived from
recrystallized 2a shows almost same reflections as
Figure 3b. We attempted a single crystal X-ray analysis of
the photolyzed crystals; however, sufficient reflections for
the analysis were not obtained.
Figure 3. X-ray diffraction pattern for the transformation of 1a to 2a.
(a) Starting material 1a. (b) Irradiated crystals at 100% conversion.
(c) Recrystallized 2a from CHCl3–hexane solution.
In the case of 1b, photolysis of a 0.02 M benzene solution
gave the corresponding cyclobutane 2b in 50% yield
accompanied by a complex mixture (Table 1, entry 3).
Decreasing the concentration to 0.01 M did not improve the
chemical yield. On the other hand, when the powdered
crystals of 1b were irradiated, a chemoselective reaction
occurred and only cyclobutane 2b was isolated. However,
the reaction was slower than that of 1a; furthermore, the
solid gradually became amorphous by prolonged
irradiation, The solid melts down after 6 h of irradiation;
cyclobutane 2b was formed in 100% yield (46% conversion
yield) at this point (entry 4). Prolonged irradiation resulted
in decreasing the chemical yield of 2b (entry 5), because of
the formation of a complex mixture. Figure 4a shows the
XRD pattern of 1b, and Figure 4b exhibits those of 46%
conversion yield, which shows that the reflections derived
from 1b decreased with no new reflection. In all cases, no
coumarin dimer was detected at all.
Figure 1. (a) ORTEP view of 1a. (b) ORTEP view of 1b.
When a 0.02 M benzene solution of the amide 1a was
irradiated with a 500 W high-pressure mercury lamp under
argon atmosphere, intermolecular 2C2 photocyclization
proceeded and multi-cyclic cyclobutane 2a was obtained in
98% yield (Table 1, entry 1). The structure of 2a was
determined on the basis of its spectral data. Finally, the
structure was unequivocally established by single crystal
X-ray crystallographic analysis (Fig. 2).
Figure 2. ORTEP view of the photoproduct 2a.
When the powdered crystals of 1a were irradiated, the solid-
state photoreaction proceeded more effectively than the
reaction in solution (Table 1, entries 1–2). Furthermore, the
crystal-to-crystal behavior was confirmed on the basis of
Figure 4. X-ray diffraction pattern for the transformation of 1b to 2b.
(a) Starting material 1b. (b) Transition pattern (irradiated for 6 h, 46%
conversion).

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M. Sakamoto et al. / Tetrahedron 62 (2006) 3028–3032
Figure 5. Packing diagram of 1a. (a) A view from a-axis. (b) A view from b-axis. (c) A view from c-axis.
Figure 6. Packing diagram of 1b. (a) A view from a-axis. (b) A view from b-axis. (c) A view from c-axis.
In both cases, the solid-state irradiation did not give
coumarin dimer but yielded cyclobutane via intramolecular
cycloaddition. Matsuura and Venkatesan independently
reported photodimerization of coumarin derivatives in the
solid-state.5a,d In Venkatesan’s case, the distance between
atom. In the case of 1a, the reaction proceeded retaining the
crystallinity, where both reacting carbon atoms are placed
˚
closely, 3.59 and 3.83 A for d1 and d2, respectively. Then
the C–C bond formation leading to a cyclobutane ring does
not need drastic atomic reorientation. However, the reaction
of 1b occurred rather more slowly than that of 1a, and the
solid changed to amorphous according to the progress of the
reaction. The fact is reasonably explainable on the basis of
the molecular conformation of which the d2 value for 1b
˚
each reacting alkenyl bond was 3.81–3.87 A, which is
˚
much shorter than the Schmidt’s rule, !4.2 A. In the cases
of 1a and 1b, photodimerization was not observed and
effective intramolecular cycloaddition occurred exclusively.
The packing diagram clearly indicates the reason for their
reactivities. Figures 5 and 6 show the packing image of 1a
and 1b, respectively. In both cases, planes of coumarin
make parallel position in the crystal; however, the reacting
double bonds were placed far away. In the case of 1a, the
˚
exceeds 4.2 A. This is because of the steric repulsion
between the methyl group at the 4-position and the allyl
group, which keep away each reacting double bond.
Furthermore, the formation of cyclobutane, in which the
sp2 carbon atom at the C4 position transformed to sp3
hybridization, needs considerably dramatic movement of
the methyl group at the C4 position. The difference in
photochemical reactivity was explainable on the basis of
the molecular conformation in the crystal lattice.
˚
˚
center-to-center distance was 7.0 A, and 5.1 A for 1b; their
˚
value was over 4.2 A.
The conformational factor plays a very important role in the
intramolecular cycloaddition reaction in the solid-state
reaction, because interconversion involving a dramatic
movement of the atoms cannot usually occur. Table 2
shows the distances between each reacting alkenyl carbon
In conclusion, when N,N-diallylcoumarin-3-carboxamides
were irradiated in solution and in the solid-state. The
stereoselective cyclobutane formation was observed because
of the reacting alkenyl group was placed intramolecularly,
and was proceeded more effectively than the dimerization of
coumarin chromophore. Whereas the solid-state photolysis
of the coumarincarboxamide with a methyl group at the
4-position afforded an amorphous compound according to
the progress of the reaction, that of the corresponding amide
with no substituent gave quantitative yield of cyclobutane,
where the crystallinity was maintained after 100% conver-
sion, and the crystal-to-crystal manner was confirmed by
XRD analysis. This reaction provides a fine example of
stereo-controlled intramolecular photocycloaddition reaction
of hetero aromatics.
Table 2. Distances between the reacting carbon atoms
d2
N
d1
R
O
O
O
˚
Distance (A)
Coumarin
d1
d2
1a
1b
3.59
3.68
3.83
4.21

M. Sakamoto et al. / Tetrahedron 62 (2006) 3028–3032
3031
3. Experimental
46.9, 51.2, 117.5, 118.4, 119.1, 119.9, 124.0, 125.1, 125.5,
132.4, 132.7, 133.3, 149.4, 153.3, 158.6; HR-MS (FAB).
Anal. 284.1287 Calcd for C17H17NO3 (MHC). Found: m/z
284.1275 (MHC).
NMR spectra were recorded on CDCl3 solutions on a
BRUKER 300 operating 300 MHz, respectively, for 1H and
13C NMR spectroscopy. Chemical shifts are reported in
parts per million (ppm) relative to TMS as internal
standards. UV spectra were measured with a JASCO
model V-570 UV/VIS/NIR spectrophotometer. IR spectra
were recorded on a JASCO FT/IR-230 spectrometers as KBr
disks, unless otherwise noted.
X-ray crystallographic data of 1b. Orthorhombic space
˚
˚
group Pbca, aZ24.705(9) A, bZ15.742(6) A, cZ
3
3
˚
˚
7.728(4) A, VZ3005.0(2) A , ZZ8, rZ1.252 g/cm ,
m(Cu Ka)Z0.70 mmK1. The structure was solved by the
direct method of full-matrix least-squares, where the final R
and Rw were 0.056 and 0.180 for 1712 reflections, CCDC
268497 contains crystallographic data.
3.1. General procedure for the preparation of
N,N-diallylcoumarincarboxamides 1a and 1b
3.2. General procedure for the photochemical reaction
in benzene
Both coumarincarboxamides 1a–1b were provided from
corresponding coumarincarboxylic acid7 and diallyl amine.
A synthesis of 1a was exemplified as follows. To a toluene
solution containing 1.5 g (5.5 mmol) of coumarincarboxylic
acid and triethylamine 0.80 g (8.0 mmol) was added 0.79 g
(6.6 mmol) of thionyl chloride at 0 8C. The reaction mixture
was stirred for 0.5 h, and then diallylamine 1.4 g
(14.0 mmol) was added dropwise. After the reaction
mixture was stirred for 1 h, water was added, and extracted
as a usual manner. After toluene was evaporated in vacuo
and the residual mixture was subjected to chromatography
on silica gel and the crystalline amide 1a was recrystallized
from ethanol; afforded colorless plates. The structures of 1a
and 1b were determined on the basis of spectral data, mass
spectroscopy, and unequivocally X-ray crystallographic
analyses.
A benzene solution of amides 1a–1b (0.02 M) was purged
with deoxygenated and dried argon for 15 min prior
to photolysis and was irradiated with a 500-W Eikosha
high-pressure mercury lamp through a Pyrex filter. After
irradiation, benzene was evaporated and the photolysate was
chromatographed on silica gel (Merk Kieseigel 60) with
ethyl acetate–hexane (10/1) as the eluent.
3.3. General procedure for the photochemical reaction
in the solid-state
Solid samples were irradiated as a powder sandwiched
between Pyrex glasses in the inside of a polyethylene bags
and was fixed out side of a emersion well apparatus. After
irradiation, the photolysate was treated as same as that in
solution photochemistry.
3.1.1. N,N-Diallylcoumarincarboxamides 1a. The title
compound was obtained colorless plates from ethanol; mp
127–129 8C; IR (cmK1, KBr) 1631, 1712; 1H NMR (CDCl3)
d 3.87 (d, JZ5.6 Hz, 2H, CH2), 4.15 (d, JZ5.4 Hz, 2H,
CH2), 5.14–5.36 (m, 4H, 2!C]CH2), 5.78–5.84 (m, 2H,
2!CH]CH2), 7.28–7.38 (m, 2H, ArH), 7.51–7.59 (m, 2H,
ArH), 7.83 (s, 1H, 4-CH); 13C NMR 47.2, 51.2, 117.2,
118.3, 118.6, 125.3, 125.9, 128.9, 132.2, 133.1, 133.4,
142.3, 154.4, 158.5, 165.4; HR-MS (FAB). Anal. 270.1130
Calcd for C16H15NO3 (MHC). Found: m/z 270.1124
(MHC).
3.3.1. Photoproduct 2a. The title compound was obtained
colorless prisms from a mixture of CHCl3–hexane; mp 162–
1
163 8C; IR (cmK1, KBr) 1691, 1745; H NMR (CDCl3) d
2.37–2.66 (m, 2H, CH2), 3.23 (d, JZ10.5 Hz, 1H, CH), 3.44
(dd, JZ22.4, 7.8 Hz, 1H, CH), 3.68 (m, 1H, CH), 3.92, (d,
JZ6.2 Hz, 1H, CH), 3.97–4.18 (m, 2H, CH), 5.28–5.37 (m,
2H, C]CH2), 5.77–5.88 (m, 1H, CH]C), 7.04–7.30 (m,
4H, ArH); 13C NMR 35.2, 36.5, 37.2, 46.2, 51.9, 52.1,
118.0, 119.2, 123.5, 125.9, 128.6, 129.2, 131.9, 150.4,
164.6, 171.1; HR-MS (FAB). Anal. 270.1130 Calcd for
C16H16NO3 (MHC). Found: m/z 270.1124 (MHC).
X-ray crystallographic data of 1a. Triclinic space group
˚
˚
˚
P-1, aZ6.516(2) A, bZ7.101(3) A, cZ16.027(4) A, aZ
3
˚
89.93(3)8, bZ81.48(2)8, gZ69.12(3)8, VZ684.1(4) A ,
ZZ2, rZ1.307 g/cm3, m(Cu Ka)Z0.74 mmK1. The struc-
ture was solved by the direct method of full-matrix least-
squares, where the final R and Rw were 0.051 and 0.226 for
2345 reflection. CCDC 268496 contains crystallographic
data. These crystallographic data can be obtained free of
charge via www.ccdc.cam.ac.uk (or from the CCDC, 12
Union Road, Cambridge CB2 1EZ, UK; fax: C44 1223
336033 (e-mail: deposit@ccdc.cam.ac.uk).
X-ray crystallographic data of 2a. Orthorhombic space
˚
˚
group Pbca, aZ16.019(3) A, bZ15.451(3) A, cZ
3
3
˚
˚
10.799(3) A, VZ2672.7(10) A , ZZ8, rZ1.339 g/cm ,
m(Cu Ka)Z0.76 mmK1. The structure was solved by the
direct method of full-matrix least-squares, where the final R
and Rw were 0.058 and 0.119 for 2881 reflections, CCDC
268498 contains crystallographic data.
3.3.2. Photoproduct 2b. The title compound was obtained
colorless prisms from a mixture of CHCl3–hexane; mp
80–82 8C; IR (cmK1, KBr) 1685, 1750; 1H NMR (CDCl3) d
1.54 (s, 3H), 2.18–2.24 (dd, JZ8.0, 12.0 Hz, 1H), 2.55–2.62
(dd, JZ8.5, 12.0 Hz, 1H), 3.16–3.24 (m, 1H), 3.58–3.64 (m,
1H), 3.91–3.98 (m, 1H), 4.20–4.27 (m, 2H), 5.27–5.36 (m,
2H), 5.77–5.88 (m, 1H), 7.03–7.06 (m, 1H), 7.21–7.30
(m, 3H); 13C NMR 27.2, 34.0, 41.8, 42.6, 46.1, 51.8, 56.1,
118.0, 119.0, 126.0, 119.1, 126.0, 127.7, 128.6, 129.2,
3.1.2. N,N-Diallyl-4-methylcoumarincarboxamides 1b.
The title compound was obtained colorless needles from a
mixture of CHCl3–hexane; mp 85–87 8C; IR (cmK1, KBr)
1630, 1714; 1H NMR (CDCl3) d 2.44 (s, 3H, CH3), 3.85 (d,
JZ5.8 Hz, 2H, CH2), 4.14–4.25 (m, 2H, CH2), 5.10–5.38
(m, 4H, 2!C]CH2), 5.69–5.78 (m, 1H, CH]CH2), 5.83–
5.91 (m, 1H, CH]CH2), 7.30–7.38 (m, 2H, ArH), 7.51–
7.59 (m, 1H, ArH), 7.64–7.68 (m, 1H, ArH); 13C NMR 16.7,

3032
M. Sakamoto et al. / Tetrahedron 62 (2006) 3028–3032
3. (a) Photochemistry in Organized and Constrained Media;
Ramamurthy, V., Ed.; VCH: New York, 1991. (b) Desiraju,
G. R. Crystal Engineering: The Design of Organic Solids;
Elsevier: Amsterdam, 1989. (c) Hasegawa, M. Chem. Rev.
1983, 85, 507–518. (d) Matsumoto, A. In Toda, F., Ed.; Topics
in Current Chemistry: Organic Solid-State Reactions; Springer:
Berlin, 2005; Vol. 254, pp 263–305.
132.2, 149.4, 169.5; HR-MS (FAB). Anal. 284.1287 Calcd
for C17H18NO3 (MHC). Found: m/z 284.1274 (MHC).
Acknowledgements
This work was supported by a Grant-in-Aid for Scientific
Research on Priority Area (417) from the Ministry of
Education, Culture, Sports, Science and Technology
(MEXT) of the Japanese Government.
4. Intramolecular 2C2 cyclobutane formation in the solid-state has
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Tham, F. S.; Kulling, R. K. J. Am. Chem. Soc. 1992, 114,
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Tetrahedron Lett. 1992, 33, 6465–6468. (c) Vishnumurthy, K.;
Row, T. N. G.; Venkatesan, K. J. Chem. Soc., Perkin Trans. 2
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Brett, T. J.; Alexander, J. M.; Clark, J. J.; Ross, C. R., II;
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