X-Ray and MO analysis of highly stereoselective solid-state photocycloadditions of 2-pyrones with maleimide

Article abstract of DOI:10.1016/S0040-4020(02)00582-3

Photoirradiations of grinding mixtures of 4-(ω-arylalkyloxy)-6-methyl-2-pyrones 1i-1o and maleimide 2 in the solid state quantitatively gave only a [2+2] cycloadduct 3j with high stereoselectivity. The 1:1 complex crystals 1j·2, and 1a·2, 1b·2, 1c·2, 1d·2, 1g·2, 1h·2 from another 2-pyrones with 2, were characterized by powder X-ray diffraction technique. The crystal formation was remarkably affected by polar and bulky nature of the substituents at the aryl groups. Four kinds of hydrogen bondings by two ground state species for the crystals were quantitatively estimated, and the photoreaction mechanism was analyzed to proceed via some interactions of the singlet excited state of 1 with ground state of 2 by MO transition state calculation.

Full text of DOI:10.1016/S0040-4020(02)00582-3

TETRAHEDRON
Pergamon
Tetrahedron 58 -2002) 6111±6116
X-Ray and MO analysis of highly stereoselective solid-state
photocycloadditions of 2-pyrones with maleimide
Tetsuro Shimo,a Takahiro Uezono,a Toru Obata,a,² Mikio Yasutake,b Teruo Shinmyozub
and Kenichi Somekawaa,p
aDepartment of Applied Chemistry and Chemical Engineering, Faculty of Engineering, Kagoshima University, Korimoto 1-21-40,
Kagoshima 890-0065, Japan
bInstitute for Fundamental Research of Organic Chemistry )IFOC), Kyushu University, Hakozaki 6-10-1, Higashi-ku,
Fukuoka 812-8581, Japan
Received 30 April 2002; accepted 27 May 2002
AbstractÐPhotoirradiations of grinding mixtures of 4--v-arylalkyloxy)-6-methyl-2-pyrones 1i±1o and maleimide 2 in the solid state
quantitatively gave only a [212] cycloadduct 3j with high stereoselectivity. The 1:1 complex crystals 1j´2, and 1a´2, 1b´2, 1c´2, 1d´2,
1g´2, 1h´2 from another 2-pyrones with 2, were characterized by powder X-ray diffraction technique. The crystal formation was remarkably
affected by polar and bulky nature of the substituents at the aryl groups. Four kinds of hydrogen bondings by two ground state species for the
crystals were quantitatively estimated, and the photoreaction mechanism was analyzed to proceed via some interactions of the singlet excited
state of 1 with ground state of 2 by MO transition state calculation. q 2002 Elsevier Science Ltd. All rights reserved.
1. Introduction
2. Results and discussion
The solid-state photoreactions of two different organic
molecules give us much attention from the viewpoint of
controlling the selectivities of the reactions1±4 because of
the tight and regular arrangement of the molecules in the
crystals, using a non-covalent interaction. Recently we have
succeeded in achieving a high selective [212] cycloaddition
with high ef®ciency by irradiation to 1:1 complex crystals
between 2-pyrones 1a±1d, 1g, 1h and maleimide 2 to give
3a±3d, 3g and 3h -Scheme 1).5,6 Our strategy is based on
constructing the regularly arranged two sets of different
molecules by using some intermolecular interactions such
as hydrogen bonding, electrostatic interaction, p±p stack-
ing and/or CH±p interaction -Scheme 2). We have planned
to extend this reaction to 4--v-arylalkyloxy)-6-methyl-2-
pyrones -1i±1o) to clarify the solid-state photoreaction
more in detail by using single crystal and powder X-ray
diffraction studies, and MO calculation. The MO calculation
may suggest the interaction force such as hydrogen bond-
ings between the two ground state species and also the
excited state estimation for the photoreaction pathway.
2-Pyrones 1i±1o were prepared according to a method
described in the literature6 in 69, 38, 18, 26, 43, 31, and
9% yields, respectively. 1:1 Complex crystal 1j´2 -mp
62±648C) between 1j -mp 53±568C) and 2 -mp 92±948C)
was prepared by crystallization of the equimolar substrates
from CHCl3 and the structure was determined by an X-ray
crystallographic analysis of the single crystal similar to the
case of 1b´2.6 The crystal shows four types of hydrogen
bondings between O±CvO and HN groups with O´´´H
Ê
Ê
distance of 1.97 A, C-4)vC-3)´´´OvC±N -2.39 A),
Ê
C-6)vC-5)H´´´OvC±N -2.38 A), and 2-pyrone-O
Ê
-ether)´´´HCv -maleimide) -2.43 A). CH±p interactions
Ê
between the maleimide ole®n and benzene -3.2 A), and
Ê
p±p stacking between two benzene rings -3.7 A) were
also observed -Fig. 1). Intermolecular distances of the two
Ê
Ê
facing double bonds are 3.68 A -C-6)´´´C-13)) and 3.84 A
-C-5)´´´C-14)) -Fig. 2). The hydrogen bondings were also
suggested from the lower wavelength shifts of the carbonyl
groups in the IR spectra: lactone and imide carbonyls
showed 20 and 10 cm21 shifts. Irradiation to the complex
crystal 1j´2 at room temperature for 24 h gave [212]
cycloadduct 3j in 80% yield as a sole product together
with recovery of 1j´2 -18%). Irradiation to the grinding
equimolar mixture between 1j and 2 also afforded 3j in
74% yield and recovery of 1j´2 -23%). Since 1:1 complex
crystals of 1i´2, 1k´2, 1l´2, 1m´2, 1n´2, and 1o´2 were dif®-
cult to prepare by crystallization method, irradiation was
carried out to each mixture of 1i and 2, 1k and 2, 1l and
Keywords: solid-state photochemistry; cycloaddition; 2-pyrones; hydrogen
bonding; transition state analysis.
p
Corresponding author. Tel.: 181-99-285-8330; fax: 181-99-285-8334;
e-mail: some@apc.kagoshima-u.ac.jp
Present address: Kagoshima Prefectural Institute of Industrial Technol-
ogy, 1445-1, Oda, Hayato-cho, Kagoshima, 899-5105, Japan.
²
0040±4020/02/$ - see front matter q 2002 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020-02)00582-3

6112
T. Shimo et al. / Tetrahedron 58 )2002) 6111±6116
Scheme 1.
2, 1m and 2, 1n and 2, and 1o and 2 prepared by grinding
each substrates. But no cycloadduct was obtained from each
irradiation. From these facts in addition to the results of
previous report6 as shown in Scheme 1, it was found that
2-pyrones having aromatic alkyloxy group such as
m-methylbenzyloxy group 1j, p-methylbenzyloxy group
1d, p-biphenylmethyloxy group 1g, and 1-naphthylmethyl-
oxy group 1h afforded 1:1 complex crystals with 2 together
with their cycloadducts upon irradiation to the complex
crystals. 4--m-Methoxybenzyloxy)-6-methyl-2-pyrone also
gave a 1:1 complex crystal with 2.7 On the other hand,
2-pyrones possessing o-methylbenzyloxy group 1i,
o-biphenylmethyloxy group 1m, p-chloromethylbenzyloxy
group 1k, p-chlorobenzyloxy group 1l, p-methoxybenzyl-
oxy group 1e, p-nitrobenzyloxy group 1f, and 9-anthryl-
Scheme 2.
Figure 1. Molecular packing diagram of 1j´2 showing hydrogen bondings, CH±p, and p±p interactions.

T. Shimo et al. / Tetrahedron 58 )2002) 6111±6116
6113
Figure 2. Molecular packing diagram of 1j´2 showing two facing double bonds.
methyloxy group 1o gave neither 1:1 complex crystal 1´2
nor photocycloadduct 3. Although van der Waals radius of
adduct 3g in 63 and 80% yields, respectively. The PXD
patterns for the grinding mixtures of 1a and 2, 1b and 2,
1c and 2, 1d and 2, 1h and 2, and 1j and 2 showed new peaks
which were described in experimental section similar to the
case of the grinding mixture of 1g and 2. On the other hand,
the PXD patterns of the grinding mixtures of 1e and 2, 1f
and 2, and 1i and 2, whose mixtures gave no 1:1 complex
crystal by crystallization and also afforded no cycloadduct
by irradiation, were the sum of those of the component
crystals.
Ê
chloro group -1.8 A) is smaller than that of methyl group
8
Ê
-2.0 A), 1:1 complex crystal of 1l -Rˆp-chlorobenzyl)´2
was not obtained in contrast to the formation of the crystal
1d -Rˆp-methylbenzyl)´2. Since the crystal packing
depends upon a number of polar interactions, the change
in the crystal structure caused by the polar nature of the
p-chloro group and p-chloromethyl group at the benzene
ring suggests to prevent the favorable parallel orientation
of the two sets of a 1:1 complex crystal between 1 and 2
similarly to the case of p-methoxy group or p-nitro group.6 It
seems to have moderately large cavity to allow the forma-
tion of the complex crystal at the m-position of the benzene
ring because of giving the 1:1 complex crystals in the case
of m-methyl group and m-methoxy group. In the case of
2-pyrone having methyl or phenyl group at the o-position,
it is assumed that the complex crystal was dif®cult to form
by the lack of strong intermolecular interactions between
2-pyrone and maleimide. Although 2-pyrone having
1-naphthylmethyloxy group showed p±p stacking between
two naphthyl groups in the complex crystal 1d´2,6 9-anthryl-
methyloxy group at the 2-pyrone ring also may prevent the
formation of the complex crystal 1o´2 owing to the weak
intermolecular interactions compared to the case of 1d´2.
The allowance of the substituents -polar nature, position at
the benzene ring, and size) to make the complex crystals
between 1 and 2 was clari®ed. Direct and sensitized photo-
reactions of 2-pyrones 1i, 1j, 1m with 2 in MeCN solution
gave no cycloadduct. 2-Pyrone 1l reacted with 2 in sensi-
tized photoreaction to give a complex mixture whose
products were dif®cult to isolate.
The most important intermolecular force to produce 1:1
Powder X-ray diffraction -PXD) diagrams of a grinding
mixture of 1g and 2, that of grinding mixed crystal obtained
by removal of the solvent from a solution containing 1g and
2, and that of grinding 1g´2 obtained by crystallization are
shown in Fig. 3 together with those of 1g and 2. Since the
PXD pattern for the grinding mixture of 1g and 2 for 20 min,
whose diagram showed almost the same pattern to the
complex crystal 1g´2 obtained by crystallization, cannot
be represented as a sum of 1g and 2, it is concluded that
the crystalline complex was produced by only grinding the
mixture in this system. Irradiation to the grinding mixtures
of 1g and 2 for ten and twenty minutes gave [212] cyclo-
Figure 3. Powder X-ray diffraction patterns for 1g, 2, 1g12, and 1g´2.
-a) Grinding a mixture of 1g and 2 for 10 min. -b) Grinding a mixture of
1g and 2 for 20 min. -c) Grinding a mixture of 1g and 2, which was prepared
from the evaporation of a solution containing the two substrates, for 10 min.
-d) Grinding the 1:1 complex mixture 1g´2 for 10 min.

6114
T. Shimo et al. / Tetrahedron 58 )2002) 6111±6116
Figure 4. Estimated hydrogen bond energies.
Scheme 3.
complex crystal between 1 and 2 was con®rmed to be some
hydrogen bonds from the X-ray crystal structures of the
complex crystals and from the fact that N-substituted
maleimides gave no complex crystal with 1. It has been
known that AM1 studies provide good quantitative molecu-
lar models and give a reasonable estimate for inter- and
intramolecular hydrogen bondings of water and simple
amides.9 So we estimated the hydrogen bond distances
and energies of 2-pyrone 1a, maleimide 2 and 1:1 complex
crystal 1´2 semiquantitatively by using Win MOPAC AM1
-Fujitu) method -Fig. 4). X-ray crystal structure of 1a
showed two hydrogen bonds between CvO and HCvC
state of 1a -1S1) was brought close to the 20-position of the
0
ground state of 2 - S1) from the distance of 3.63 A whose
Ê
value was obtained from the single crystal X-ray structure of
1a´2.5 First, formation of a metastable state by the endo-
approach between 1a -1S1) and 2 -0S2) gave energetic
stabilization -2.2 kcal/mol) -Fig. 5) by p-orbital overlapping
and the electrostatic interaction owing to the higher
electron density at C5 of the singlet excited state of 1a
with C19 of 2 -Fig. 6). The more stable conformer of
Ê
groups with the O´´´H distance of 2.219 A. The crystal
data were reported previously.10 In the case of 2, pairs of
2 were linked together to form planar tricyclic dimers by
pairs of intermolecular hydrogen bonds between CvO and
11
Ê
HN groups with O´´´H distance of 1.98 A. The hydrogen
Ê
bond distance of 1a and 2 were calculated to be 2.3 A and
Ê
2.1 A, respectively. The hydrogen bond energies of 1a and 2
were estimated to be 1.8 and 5.8 kcal/mol, respectively, by
the difference from the heat of formation of each compound.
The X-ray crystal structures of 1b´2, 1d´2, 1g´2 and 1h´2
Ê
showed four kinds of hydrogen bonds -1.91±2.51 A) similar
to the case of 1j´2 -Fig. 1). Such hydrogen bond distances
and total hydrogen bond energy of 1´2 were estimated to be
Figure 5. Heat of formation -HOF) of the photoreaction of 1a with 2
calculated by MOPAC AM1.
Ê
1.9±2.4 A and 6.7 kcal/mol, respectively, by the endo-
approach of the two substrates. The hydrogen bonding
energy was larger than that of 1a or 2. It is obvious from
the calculation results that 1:1 complex crystal 1´2 was
stabilized by the newly-formed two sets of hydrogen bonds.
We now describe a transition state -TS) analysis of the solid-
state photoreactions which lead to an understanding of
exclusive stereoselectivity by using the AM1 method. The
reaction mechanism of 1 with 2 was estimated to proceed
via singlet excited state of 1 from the following result as
shown in Scheme 3. The 6-position of the singlet excited
Figure 6. The electron density change of 1a from the ground state -0S1) to
the singlet excited state -1S1).

T. Shimo et al. / Tetrahedron 58 )2002) 6111±6116
6115
Ê
HOFˆ256.2 kcal/mol and coordinate rre -C5±C19)ˆ2.3 A
X-ray diffraction -PXD) patterns were obtained with Rigaku
Corp. Model No. 2013 diffractometer equipped with Cu Ka
Ê
radiation -1.54178 A). Data were collected between 15 and
308 in 2u at a scan rate of 18/min.
1
0
may be an exciplex from S1 with S2. Secondly, the ®rst
bond formation occurred at C5 with C19 via transition state
-TS1) -246.2 kcal/mol) having 7.8 kcal/mol of activation
energy and followed by the formation of cycloadduct 3
-2142.5 kcal/mol).
4.1.1. 6-Methyl-4-,2-methylbenzyloxy)-2-pyrone ,1i). A
solution of o-methylbenzyl chloride -4.2 g, 30 mmol),
4-hydroxy-6-methyl-2-pyrone -3.8 g, 30 mmol) and DBU
-5.7 g, 38 mmol) in MeCN -35 ml) was re¯uxed for 20 h.
The solution was allowed to cool to room temperature, and
was evaporated. The concentrate was submitted to column
chromatography -silica gel, ethyl acetate±hexaneˆ1:1) to
give 1i which was puri®ed by recrystallization from ethyl
acetate±hexane -1:5). 1i -2.6 g, 69% yield): mp 111±1128C;
On the other hand, the similar calculation of the triplet
excited state of 1a with ground state of 2 gave no simulation
for endo-adduct 3a. The solid-state photoreaction of 1a with
2 was also not sensitized by the addition of benzophenone.
3. Conclusions
1
IR -KBr) 1710 cm21; H NMR -DMSO-d6) d 2.17 -3H, s),
Photoirradiation to grinding mixtures of two different
components quantitatively gave [212] cycloadducts with
high stereoselectively. The controlling factors of the 1:1
complex crystals were clari®ed and the reaction mechanism
was analyzed as follows. The complex crystals of 4--v-
arylalkyloxy)-6-methyl-2-pyrones 1 with maleimide 2
were formed by newly-produced hydrogen bondings
between two substrates, which were stronger than that of
each substrate, together with CH±p interaction, p±p stack-
ing, and electrostatic interaction in the ground state, and also
in the excited state. The comlex crystals were predictable
from the powder X-ray diffraction and gave [212] cyclo-
adducts with high stereoselectivity upon irradiation. The
formation of the complex crystals also depends on the
feature of the substrate -o-, m-, or p-position, polar nature,
bulkiness) at the benzene ring of the 2-pyrone. The reaction
mechanism for the cycloaddition was elucidated via endo-
approach between singlet excited state of 1 and ground state
of 2 on the basis of MO transition state analysis.
2.29 -3H, s), 5.13 -2H, s), 5.70 -1H, s), 6.12 -1H, s), 7.24±
7.37 -4H, m); LR MS m/z 231 -M11). Anal. Calcd for
C14H14O3: C, 73.03; H, 6.13. Found: C, 72.92; H, 6.12.
4.1.2. 6-Methyl-4-,3-methylbenzyloxy)-2-pyrone ,1j). 1j
was prepared by a method similar to that of 1i by using
m-methylbenzyl chloride -1.4 g, 10 mmol), 4-hydroxy-6-
methyl-2-pyrone -1.3 g, 10 mmol) and DBU -1.8 g,
12 mmol). 1j -0.95 g, 38% yield): mp 53±568C; IR -KBr)
1740 cm21; 1H NMR -DMSO-dl6) d 2.17 -3H, s), 2.32 -3H,
s), 5.09 -2H, s), 5.62 -1H, s), 6.12 -1H, s), 7.17±7.30 -4H,
m); LR MS m/z 231 -M11). Anal. Calcd for C14H14O3: C,
73.03; H, 6.13. Found: C, 73.17; H, 6.20.
4.1.3. 4-,4-Chlorobenzyloxy)-6-methyl-2-pyrone ,1k). 1k
was prepared by a method similar to that of 1i by using 1,4-
bis-chloromethyl)benzene -1.8 g, 10 mmol), 4-hydroxy-6-
methyl-2-pyrone -2.5 g, 10 mmol) and DBU -3.0 g,
20 mmol). 1k -0.35 g, 18% yield): mp 131±1338C; IR
1
-KBr) 1725 cm21; H NMR -DMSO-d6) d 2.17 -3H, s),
4.77 -2H, s), 5.12 -2H, s), 5.62 -1H, s), 6.11 -1H, s),
7.42±7.49 -4H, m); LR MS m/z 265 -M11). Anal. Calcd
for C14H13ClO3:C, 63.52; H, 4.91. Found: C, 63.67; H, 5.00.
4. Experimental
4.1. General
4.1.4. 4-,4-Chlorobenzyloxy)-6-methyl-2-pyrone ,1l). 1l
was prepared by a method similar to that of 1i by using
p-chlorobenzylchloride -8.0 g, 50 mmol), 4-hydroxy-6-
methyl-2-pyrone -6.3 g, 50 mmol) and DBU -7.7 g,
50 mmol). 1l -3.3 g, 26% yield): mp 144±1468C; IR
All melting points are uncorrected. NMR spectra were
measured at 400 MHz on the JNM GSX-400 -TMS as an
internal standard). IR spectra were recorded with a JASCO
IR Report-100 spectrometer as KBr disks. Mass spectra
were recorded with a JEOL JMS-HX110 A-FAB MS)
using m-nitrobenzyl alcohol as matrix. Elemental analyses
were made using a Yanaco MT-5. Photoirradiations were
carried out in a Pyrex tube by using Riko 400 W high
pressure mercury lamp.
1
-KBr) 1740 cm21; H NMR -CDCl3) d 2.22 -3H, s), 4.97
-2H, s), 5.46 -1H, s), 5.83 -1H, s), 7.30, 7.38 -each 2H, d,
Jˆ8.4 Hz); LR MS m/z 251 -M11). Anal. Calcd for
C13H11ClO3: C, 62.29; H, 4.42. Found: C, 62.45; H, 4.45.
4.1.5. 4-,2-Biphenylmethyloxy)-6-methyl-2-pyrone ,1m).
1m was prepared by a method similar to that of 1i by using
2-phenylbenzylbromide -2.6 g, 10 mmol), 4-hydroxy-6-
methyl-2-pyrone -1.3 g, 10 mmol) and DBU -1.8 g,
12 mmol). 1m -0.57 g, 43% yield): mp 83±868C; IR
Single crystal X-ray diffraction analyses of 1a and 1j´2 were
performed on a Rigaku RAXIS-RAPID Imaging diffract-
ometer with graphite-monocromated Mo Ka radiation.
Lorentz and polarization corrections were applied to the
intensity data. The structures were solved by direct methods
using MITHRIL9012 and re®ned by a full-matrix least-
squares method. The non-hydrogen atoms were re®ned
isotropically. All calculations were performed using the
1
-KBr) 1740 cm21; H NMR -DMSO-d6) d 2.15 -3H, s),
4.97 -2H, s), 5.42 -1H, s), 6.04 -1H, s), 7.34±7.56 -9H,
m); LR MS m/z 293 -M11). Anal.Calcd for C19H16O3: C,
78.06; H, 5.52. Found: C, 77.92; H, 5.51.
³
teXsan13 crystallographic software package. Powder
4.1.6. 6-Methyl-4-diphenylmethyloxy-2-pyrone ,1n). 1n
was prepared by a method similar to that of 1i by using
diphenylbbromomethane -7.4 g, 30 mmol), 4-hydroxy-6-
methyl-2-pyrone -3.8 g, 30 mmol) and DBU -4.5 g,
³
Crystallographic data have been deposited at the CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK and copies can be obtained on request, free of
charge, by quoting the publication citation and the deposition number
186849 for 1j´2.

6116
T. Shimo et al. / Tetrahedron 58 )2002) 6111±6116
30 mmol). 1n -2.7 g, 31% yield): mp 138±1408C; IR -KBr)
1725 cm21; 1H NMR -DMSO-d6) d 2.17 -3H, s), 5.48 -1H,
s), 6.24 -1H, s), 6.67 -1H, s), 7.31±7.46 -10H, m); LR MS m/
z 293 -M11). Anal.Calcd for C19H16O3: C, 78.06; H, 5.52.
Found: C, 77.85; H, 5.57.
Jˆ11.6 Hz), 4.96 -1H, d, Jˆ11.6 Hz), 5.09 -1H, s), 7.18±
7.31 -4H, m), 11.47 -1H, s); LR MS m/z 328 -M11). Anal.
Calcd for C18H17NO5: C, 66.04; H, 5.54; N, 4.28. Found: C,
65.84; H, 5.24; N, 4.40.
4.2. PXD data of 2-pyrones 1, maleimide 2, and grinding
mixtures of 1 and 2
4.1.7. 4-,9-Anthrylmethyloxy)-6-methyl-2-pyrone ,1o).
1o was prepared by a method similar to that of 1i by using
9-chloromethylanthracene -2.3 g, 10 mmol), 4-hydroxy-6-
methyl-2-pyrone -1.3 g, 10 mmol) and DBU -1.8 g,
12 mmol). 1o -0.13 g, 9% yield): mp 167±1708C; IR
1a: 2uˆ26.7; 2: 2uˆ28.2; grinding mixture of 1a and 2 for
20 min: 2uˆ14.1, 26.8, 28.3; 1b: 2uˆ16.9, 21.6, 23.7, 25.1,
26.4, 27.9; grinding mixture of 1b and 2 for 10 min:
2uˆ16.3, 22.8, 23.3, 25.2, 27.6, 28.3; 1c: 2uˆ14.8, 15.6,
23.2, 23.5, 24.3, 24.6, 31.5; grinding mixture of 1c and 2 for
10 min: 14.3, 18.0, 18.3, 22.5, 23.5, 27.4, 28.3, 28.8; 1d:
2uˆ15.8, 16.4, 19.8, 23.9, 25.4, 25.8, 26.1, 26.3; grinding
mixture of 1d and 2 for 10 min: 2uˆ15.6, 16.2, 17.5, 19.6,
22.3, 23.9, 25.8, 27.0, 28.3; 1g: 2uˆ16.6, 21.8, 22.9, 23.9,
27.4; grinding mixture of 1g and 2 for 20 min: 2uˆ14.1,
18.3, 22.5, 24.0, 27.5, 28.3; 1h: 2uˆ15.4, 17.5, 21.8, 23.8,
26.1, 27.3; grinding mixture of 1h and 2 for 10 min:
2uˆ15.4, 21.7, 23.9, 26.1, 26.4, 27.3, 28.3; 1j: 2uˆ14.8,
21.6, 22.5, 23.6, 26.0, 26.3, 26.8; grinding mixture of 1j and
2 for 10 min: 2uˆ17.4, 17.6, 22.0, 23.5, 24.5, 26.4, 27.8.
1
-KBr) 1740 cm21; H NMR -DMSO-d6) d 2.16 -3H, s),
6.03 -1H, s), 6.08 -1H, s), 6.13 -2H, s), 7.56±7.65 -4H,
m), 8.16±8.32 -2H, m), 8.76 -1H, s); LR MS m/z 317
-M11). Anal. Calcd for C21H16O3: C, 79.73; H, 5.10.
Found: C, 79.27; H, 5.11; HR MS -M11) Calcd for
C21H17O3 317.1178. Found 317.1165.
4.1.8. 1j´2 1:1 Complex crystal. Amixture of 1j -92 mg,
0.40 mmol) and 2 -39 mg, 0.40 mmol) was dissolved in 3 ml
of hot CHCl3. The solvent was allowed to cool at room
temperature, during which ®ne crystals were found. After
crystallizing overnight, the crystals were collected by ®ltra-
tion, then dried in vacuo to afford 1j´2 -125 mg, 96% yield,
mp 62±648C) as colorless plates. 1H NMR con®rmed a 1:1
ratio of 1j´2.
References
1. Ito, Y. Synthesis 1998, 1±32 and references cited therein.
2. Ito, Y.; Fujita, H. Chem. Lett. 2000, 288±289.
3. Tanaka, K.; Toda, F. Chem. Rev. 2000, 100, 1025±1074 and
references cited therein.
Single crystal X-ray diffraction analysis of 1j´2. Crystal
structure data for 1j´2: formula C18H17NO5. Mˆ327.34,
crystal dimensions 0.30£0.10£0.10 mm, monoclinic,
Ê
Ê
space group C2/c-#15), aˆ24.052 -3) A, bˆ6.521 -1) A,
Ê
Ê
Ê 3
4. Koshima, H.; Matsushige, D.; Miyauchi, M.; Fujita, J.
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cˆ22.406 -3) A, bˆ114.444 -7) A, Vˆ3199.0 -9) A ,
Zˆ8, rcalcdˆ1.3598 g cm23, 2umaxˆ55.08, Tˆ93.0 K, R
-Rw)ˆ0.068 -0.188) for 1840 re¯ection data with I.2s-I)
and 220 variables, GOFˆ0.96.
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Kawaminami, M.; Yoshida, R.; Somekawa, K. Tetrahedron
2001, 57, 1531±1541.
4.1.9. 7-Methyl-11-m-methylbenzyloxy-8-oxa-4-azatri-
,3j)
cyclo[5.4.0.02,6]undec-10-en-3,5,9-trione
,endo
7. Shimo, T.; Yano, H.; Yasutake, M.; Shinmyozu, T.;
Somekawa, K. Anal. Sci. 2002 in press.
adduct) from the photolysis of 1j´2. Crystals of 1j´2
-125 mg, 0.38 mmol) prepared by crystallization were sand-
wiched with two Pyrex glass plates and photolyzed for 24 h
under nitrogen atmosphere at room temperature. The reac-
tion solid was washed with CHCl3 -5 ml) to remove the
starting materials and the resulting solid was ®ltered to
give 3j -99 mg, 80% yield), which was recrystallized from
MeCN. The starting material 1j´2 was recovered from the
concentration of the CHCl3 ®ltrate -18%). Amixture of 1j
-125 mg, 0.54 mmol) and 2 -53 mg, 0.54 mmol) grinding
for 20 min was irradiated for 24 h. The same workup, as
mentioned above, gave 3j in 74% yield together with
recovery of the starting materials -23%). Mp 254±2578C;
8. Pauling, L. The Nature of the Chemical Bonds; Cornell
University: Ithaca, NY, 1960; p 260.
9. -a) Dewar, M. J. S.; Jie, C.; Yu, J. Tetrahedron 1993, 49,
5003±5038. -b) Dado, D.; Gellman, S. H. J. Am. Chem. Soc.
1992, 114, 3138±3139.
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2580.
12. Gilmore, C. J. MITHRIL: An integrated direct methods
computer program; University of Glasgow, Scotland, 1990.
13. Crystal Structure Analysis Package; Molecular Structure
Corporation, 1985 and 1999.
1
IR -KBr) 1715, 1685 cm21; H NMR -DMSO-d6) d 1.60
-3H, s), 2.33 -3H, s) 3.42 -1H, d, Jˆ6.4 Hz), 3.55 -1H, dd,
Jˆ6.4, 9.6 Hz), 3.68 -1H, d, Jˆ9.6 Hz), 4.80 -1H, d,