Stereoselective Photodimerization of 3-Arylindenones in Solution and in the Solid State

Article abstract of DOI:10.1021/acs.joc.7b03147

Photodimerization of 3-arylindenones in solution and in the solid state was examined. Irradiation of 3-arylindenones in benzene exclusively gave C₂-symmetric anti-HH cyclobutane dimers in good yields. In contrast, photolysis in the solid state

Full text of DOI:10.1021/acs.joc.7b03147

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Article
Stereoselective Photodimerization of 3–
Arylindenones in Solution and in the Solid-State
Naohiro Uemura, Hiroki Ishikawa, Naoki Tamura, Yasushi Yoshida,
Takashi Mino, Yoshio Kasashima, and Masami Sakamoto
J. Org. Chem., Just Accepted Manuscript • DOI: 10.1021/acs.joc.7b03147 • Publication Date (Web): 17 Jan 2018
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Stereoselective Photodimerization of 3–Arylindenones in Solution and in
the Solid-State
Naohiro Uemura,† Hiroki Ishikawa,† Naoki Tamura,† Yasushi Yoshida,† Takashi Mino,† Yoshio
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Kasashima,‡ Masami Sakamoto*,†
†Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, and Molecular Chirality Research
Center, Yayoi-cho, Inage-ku, Chiba 265-8522, Japan
‡Education Center, Faculty of Creative Engineering, Chiba Institute of Technology, Shibazono, Narashino, Chiba 275-0023,
Japan
ABSTRACT: Photodimerization of 3-arylindenones in solution and in the solid-state was examined. Irradiation of 3-arylindenones
in benzene exclusively gave C2-symmetric anti-HH cyclobutane dimers in good yields. In contrast, photolysis in the solid-state
afforded syn-HH cyclobutane dimers efficiently, which was considerably influenced by the molecular arrangement in the crystal
lattice.
■ INTRODUCTION
derivatives afforded the corresponding [2+2] dimers. Sommer
reported the formation of only anti-HH dimers under the condi-
tions of an ethereal solution photoreaction. We found that the
solid-state photochemical reaction gave completely different ste-
reoselectivity upon photodimerization.
Indenones are very important scaffolds in natural products1-2 and
pharmaceutical materials. Additionally, they have been widely
used for the synthesis of various biologically active compounds
such
as estrogen
receptors,3 gibberellins,4 C-nor-D-
homosteroids,5-7 and non-peptidic antagonists targeting endothelin
receptors.8-9 Indenones have an enone structure and their photo-
chemical behavior has been widely studied since enones are in-
volved in many applied reactions in organic synthesis.10-13
With regard to the stereoselective photochemical cyclobutane
formation of enones, we are interested in the regioselectivity of
their [2 + 2] photodimerization, because cyclobutanes are also
very important materials in natural products, pharmaceutical
agents, and functional materials.14-15 Many regio- and stereo-
selective photodimerizations have been achieved by wonderful
methods for molecular arrangement such as using solid-state reac-
tions,16,17 host-guest complexes,18,19 etc.20-23 Especially in the
solid-state reaction, the assembly and packing of molecules are of
increasing importance to control chemical reactivity.24 For a pho-
todimerization to occur in the solid state, carbon−carbon double
(C=C) bonds are generally required to be parallel and separated
<4.2 Å.25,26 Herein, we investigated the stereochemistry of the
photochemical reaction of 3-arylindenones, which are also biolog-
ically and pharmacologically important cyclic chalcone analogues,
in solution and in the solid-state, to obtain stereoselective dimers.
Scheme 1. Possible stereoisomers of photodimerization reaction
of 3-aryl-1H-inden-2-ones.
■ RESULTS AND DISCUSSION
3-Arylindenones 1a-f were synthesized from indanone through 3-
bromoindenone via the Suzuki-Miyaura coupling in moderate
chemical yields (Scheme 2).29
There are four possible stereoisomers 2-5 for cyclobutane dimers
of 3-phenylindenones 1 (Scheme 1). A few studies on photochem-
ical dimerization of 3-arylindenones have been reported by Som-
mer9,27 and McMurry,28 showing that only 4-tolyl and 4-anisyl
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tion of 1d in benzene at the concentration of 0.05 M using 365 nm
line was 0.63.
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The stereoselective photodimerization can be considered similar
to the photochemical cycloaddition of enones to alkenes.30-32
Much progress has been made in the understanding of the mecha-
nism of the processes involved.33 The formation of enone [2+2]
photocycloaddition products can be readily explained by the addi-
tion of an alkene to a photoexcited triplet enone and by the inter-
mediacy of a 1,4-diradical. In this case, the linkage between the
ends of the enones is the results of the polarity reversal in the
excited triplet state which makes the β-position of the photoexcit-
ed enone nucleophilic. This process favors a formation of a HH
adduct, and the stereochemistry is usually dominated by steric and
other interactions. 3-Arylindenones 1 with π-stacking could play
an important role leading to anti-HH adducts 2. A similar stere-
oselective photoreaction from the triplet excited state was also
Scheme 2. Synthesis of 3-arylinden-2-ones 1 used for photochem-
ical reaction. (i) hν (60 W halogen lump), NBS, AIBN, benzene,
reflux, 2 h; (ii) Et3N, 0 oC to rt, overnight; (iii) ArB(OH)2,
Pd(PPh3)4, Na2CO3, THF / EtOH / H2O, Ar, rt, 2 d.
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reported in the photodimerization of chromonecarboxylic esters.34-
Fig. 1 shows the UV-VIS absorption spectra of 1a-f. All in-
denones except 1f have a ππ* excitation band from 260 nm to 350
nm and a nπ* excitation band from 360 nm to 480 nm. Trifluoro-
methyl-substituted 1f exhibited considerably shorter absorption
bands, 270-320 nm for ππ* excitation and 320-380 nm for nπ*
excitation. All materials afforded yellow to red colored crystals
and solutions. Indenone 1c bearing an electron-donating methoxy
group exhibited a slightly longer absorption band than the other
substrates.
36
Table 1. Photodimerization reaction of 1a-f in benzene. a
entry indenone
Ar
Ph
yield of 2 (%) b recovery of 1 (%)
1
2
3
4
5
6
1a
1b
1c
1d
1e
1f
69
59
69
94
69
67
2
p-MeC6H4
p-MeOC6H4
p-FC6H4
11
17
1
p-ClC6H4
1
p-CF3C6H4
2
a 0.05 M benzene solution of 1 (100 mg) was irradiated for 1 h
using the 365 nm line from a 500 W high pressure mercury lamp.
bOnly stereoisomer 2 was produced.
In contrast to the solution photochemistry, the solid-state photore-
action exhibited completely different behavior. The solid-state
photoreaction was generally strongly influenced by molecular
arrangement in the crystals. We could obtain important infor-
mation on the molecular packing from X-ray crystallographic
analysis to understand the reactivity in the solid-state photoreac-
tion. Although 1a and 1f did not afford appropriate single crystals,
the molecular arrangements in crystals of the other derivatives
were studied in detail.
Fig. 1 Absorption spectra of 1a-f in Et2O at 1.0x10-4 mol L-1.
Sommer et al. reported the photodimerization of 1b and 1c to
afford 2b and 2c after 3 days in ethereal solutions under day-
light.13 We examined the photoreaction in detail for the series of
para-substituted 3-phenylindenones 1a-f in benzene solution and
in the solid-state. Irradiation of the nπ* excitation band using the
365 nm line in benzene solution gave efficient dimerization, lead-
ing exclusively to anti-HH dimers 2 as shown in Table 1. The
anti-HH stereochemistry of the dimers was unequivocally estab-
lished by X-ray single crystal structure analysis for 2a, 2c and 2d.
Other dimers were determined on the basis of spectral data.
In the case of 1a, this material crystallized as a yellow low-
melting solid. The powdered solid was sandwiched between Pyrex
glasses, sealed in polyethylene bags, and was irradiated in an ice-
water bath with a 500 W high pressure mercury lamp. The crys-
tals began to melt as soon as irradiation began. Since a recogniza-
ble product was not obtained at that time, irradiation was contin-
ued for 1 hour. In the end, crystals did not form and the photoly-
sate changed to an amorphous state. These reaction conditions did
not promote a solid-state photoreaction; however, some different
aspect of solution chemistry was observed and three types of di-
mers were isolated. The major stereoisomer was the anti-HH 2a
(21%) which is the same product as the reaction in solution (Table
2, entry 1). This compound was produced after the solid melted.
The two other new dimers were 3a (syn-HH) and 5a (syn-HT) in
11 and 13% yields, respectively. These structures were estab-
lished by X-ray single crystal analysis. An exact explanation for
the formation of these three dimers cannot be provided without
packing data of monomer 1a.
We also examined sensitization and quenching experiments using
1d to determine the reactive excited state. When 1d was irradiated
in the presence of thioxanthone (ET = 65.5 kcal mol-1), the dimeri-
zation reaction proceeded at almost the same rate as the direct
irradiation (Table S1). Furthermore, quenching using ferrocene
(ET = 40 kcal mol-1) as a triplet quencher was very effective, and
the dimerization was conveniently suppressed. These results
strongly supported that the direct dimerization proceeded from the
triplet excited state. The dimerization promoted considerably high
photochemical reactivity; the quantum efficiency of the consump-
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Table 2. Photodimerization reaction of 1a-f in the solid-state.
progress of the reaction, dimerization might proceed in the result-
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ing space.
entry indenone
Ar
Ph
yield of 3 (%)
recovery of 1 (%)
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6
1a
11 (21, 13) b
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79
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35
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9
1b p-MeC6H4
1c p-MeOC6H4
1d p-FC6H4
13 c
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67
1e p-ClC6H4
1f
p-CF3C6H4
a
9
Powdered solid sample (100 mg) sandwiched between Pyrex
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glasses and packed in polyethylene bags was irradiated with a 500
W high pressure mercury lamp at 0 °C for 1 h. b Numbers in pa-
renthesis show the yield of other stereoisomers, 2a in 21% yield
and 5a in 13% yield. c An unidentified complex mixture was ob-
tained.
Fig. 3. Packing diagram of 1d and atomic distances between two
F atoms, F and H atoms, and the reacting bond distance.
The crystal packing diagram of 1b showed an unfavorable pack-
ing for the dimer formation (Fig. S1). A CH-π interaction between
a C-H of the tolyl group with the benzene ring of indenone ar-
ranges the molecules in a herringbone-type packing pattern. The
ππ-interaction between each tolyl group forms a parallel arrange-
ment; however, they are located in opposite directions, and the
reacting double bonds are far apart. As a result, the reaction re-
sulted in low conversion. A syn-HH dimer 3b was obtained as the
only assignable product in 13% yield at 21% conversion accom-
panied by many unidentified products presumably formed by
polymerization and other photochemical reactions (Table 2, entry
2). The distance between the closest reacting double bonds lead-
ing to 3b is 10.5 Å, which is far from the Schmidt’s rule (reacting
double bonds should be placed in parallel and within a distance of
4.2 Å).25,26 Minor product 3b may be formed at defects or at the
surface of the powdered crystals.
X-ray analysis of 1d shows that fluorine atoms play an important
role in arranging the molecules and placing the reacting double
bonds close to each other (Fig. 3). Intermolecular interaction be-
tween fluorine atoms and aromatic hydrogen atoms are shown at
distances of 2.57 and 2.78 Å. The electrostatic interactions be-
tween the enone moieties would be also important. The distances
of C=O --- C’=O’, O=C --- C2’ and C2 --- C3’ are 3.49, 3.78, and
3.55 Å, respectively. The distance of the reacting double bonds
was also 3.83 Å. As expected from the molecular position, 1d
showed considerably high reactivity for [2+2] cycloaddition and
gave the syn-HH type adduct 3d in 55% yield (Table 2, entry 4).
Fig. 4. Packing diagram of 1e and atomic distances between two
Cl atoms, Cl and H atoms, O and H atoms, and the reacting bond
distance.
Fig. 2. Packing diagram of 1c and atomic distances between the
reacting double bonds.
In the case of 1e, molecules overlapped in the same direction
due to ππ stacking as shown in Fig. 4. The electrostatic interac-
tions between the enone moieties would be also important. The
distances of C=O --- C’=O’, O=C --- C2’ and C2 --- C3’ are 3.52,
3.79, and 3.58 Å, respectively. The molecular distance and the
reacting double bonds were placed at a distance of 3.86 Å. Inter-
action between the carbonyl oxygen with the hydrogen of the
aromatic group played an important role in connecting the col-
umns. As can be expected from the packing information, the syn-
On the other hand, when red powdered crystals of 1c were irra-
diated, the assignable product was syn-HH dimer 3c obtained in
45% yield (Table 2, entry 3). The packing diagram (Fig. 2) shows
two types of columns. In one column, two reacting atoms were
placed at a distance of 4.09 (C2 --- C2’) and 4.38 Å (C3 --- C3’).
Another column positions the reacting atoms at 4.21 (C2 --- C2’)
and 4.48 (C3 --- C3’) Å apart, which is slightly longer than the
ideal distance for [2+2] cycloaddition. However, according to the
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HH dimer 3e was predominantly obtained in 56% yield (Table 2,
entry 5).
Although single crystals could not be obtained for 1f, the solid-
state photoreaction selectively gave the syn-HH dimer 3f in 67%
yield as in the case of 1c-e (Table 2, entry 6). It is expected that
the molecules may be stacked by ππ-interactions whereby in-
denone rings preferably arrange to form syn-HH dimers.
pounds and the structure was confirmed by comparison with re-
ported spectral data.27,28,37
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3-Phenyl-1H-inden-1-one (1a).28 Compound 1a was prepared
according to the general procedure from β-bromoindenone and
phenylboronic acid to yield the title compound as a yellow solid
(0.48 g, 2.35 mmol, 49%). The crude product was recrystallized
1
from a mixed solvent of CHCl3 and hexane. M.p. 46-47 °C; H
Except for the phenyl and p-tolyl derivatives, 1a and 1b, the solid-
state photoreaction occurred efficiently, leading to syn-HH dimers.
In these cases, the aromatic rings were stacked closely in a regular
fashion by means of ππ−interactions. Furthermore, the electrostat-
ic interactions between the enone moieties and the hydrogen
bonding involving oxygen and fluorine atoms and halogen-
halogen interactions played a very important role in the arrange-
ment of molecules and their columns.
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NMR (CDCl3) δ 6.00 (s, 1H), 7.30-7.39 (m, 3H), 7.50-7.53 (m,
4H), 7.64-7.67 (m, 2H); 13C{1H} NMR (CDCl3) δ 121.6, 122.7,
122.9, 127.4, 128.91, 129.2, 130.5, 132.3, 132.8, 133.0, 143.9,
162.8, 197.1; IR (cm-1, neat) 1700; EI-MS: m/z (rel. intensity) 206
(M+, 100).
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3-(p-Tolyl)-1H-inden-1-one (1b).27 Compound 1b was prepared
according to the general procedure from β-bromoindenone and p-
tolylboronic acid to yield the title compound as a yellow solid
(0.49 g, 2.26 mmol, 47%). The crude product was recrystallized
■ CONCLUSIONS
1
from a mixed solvent of CHCl3 and hexane. M.p. 55-56 °C; H
In conclusion, we found that 3-arylindenones exhibited signifi-
cantly different photochemical behavior in solution and in the
solid-state. Irradiation in benzene solution gave anti-HH cyclobu-
tane dimers exclusively in all cases. The stereoselectivity was
reasonably explained in terms of the complementary polarity of
the triplet excited state of the enone in its ground state and the
molecular orientation in the excited state. In contrast to the solu-
tion photochemistry, the solid-state photoreaction gave syn-HH
cyclobutane dimers selectively by the influence of the molecular
arrangement which was affected by ππ-stacking in the crystal
lattices. This reaction provides a very useful method for synthe-
sizing cyclobutanes because the photodimerization proceeded
effectively and the dimers possessed modifiable functional groups
such as ketone carbonyl and indenone groups, which are biologi-
cally and pharmacologically important.
NMR (CDCl3) δ 2.45 (s, 3H), 5.99 (s, 1H), 7.31-7.33 (m, 3H),
7.38-7.39 (m, 2H), 7.52 (d, J =7.0 Hz, 1H), 7.58 (d, J = 8.1 Hz,
2H); 13C{1H} NMR (CDCl3) δ 21.5, 121.6, 122.4, 122.6, 127.4,
129.2, 129.6, 130.2, 132.5, 132.8, 141.0, 144.0, 162.9; IR (cm-1,
KBr), 1696; EI-MS: m/z (rel. intensity) 220 (M+, 71).
3-(p-Methoxyphenyl)-1H-inden-1-one (1c).27 Compound 1c was
prepared according to the general procedure from β-
bromoindenone and p-methoxyphenylboronic acid to yield the
title compound as a red solid (1.06 g, 4.5 mmol, 94%). The crude
product was recrystallized from a mixed solvent of CHCl3 and
1
hexane. M.p. 67-68 °C; H NMR (CDCl3) δ 3.89 (s, 3H), 5.97 (s,
1H), 7.03 (d, J = 8.8 Hz, 2H), 7.31-7.41 (m, 3H), 7.52 (d, J = 6,8
Hz, 1H), 7.67 (d, J = 8.8 Hz, 2H); 13C{1H} NMR (CDCl3) δ 55.4,
114.4, 121.5, 121.6, 122.4, 125.5, 129.1, 129.2, 132.6, 132.7,
143.9, 161.6, 162.4, 197.1; IR (cm-1, KBr), 1695; EI-MS: m/z (rel.
intensity) 206 (M+, 100).
■ EXPERIMENTAL SECTION
General Information. NMR spectra were recorded in CDCl3 solu-
3-(p-Fluorophenyl)-1H-inden-1-one (1d).37 Compound 1d was
prepared according to the general procedure from β-
bromoindenone and p-fluorophenylboronic acid to yield the title
compound as a yellow solid (1.06 g, 4.5 mmol, 94%). (Reported
in 78% yield). The crude product was recrystallized from a mixed
solvent of CHCl3 and hexane. M.p. 118-119 °C; 1H NMR
(CDCl3) δ 5.98 (s, 1H), 7.18-7.43 (m, 5H), 7.52-7.55 (m, 1H),
7.65-7.69 (m, 2H); 13C{1H} NMR (CDCl3) δ 116.1 (d, J = 21.9
Hz), 121.4, 122.8, 122.9, 129.1 (d, J = 3.3 Hz), 129.4, 129.5,
132.2, 132.9, 143.7, 161.6, 163.9 (d, J = 251.6 Hz), 196.9; IR
(cm-1, KBr), 1709; EI-MS: m/z (rel. intensity) 224 (M+, 100).
tions on a Bruker 300 spectrometer operating at 300 and 75 MHz,
1
respectively, for H- and 13C-NMR. Chemical shifts are reported
in parts per million (ppm) relative to TMS as an internal standard.
IR spectra were recorded on a JASCO FT/IR-230 spectrometer.
High-resolution mass spectra (HRMS) were performed on an
Orbitrap ThermoFisher Exactive ion trap mass spectrometer. X-
ray single crystallographic analysis was conducted using a
SMART APEX II (Bruker AXS) and APEX II ULTRA (Bruker
AXS). A 500 W high pressure mercury lamp (EIKOHSHA EHB-
W-500) was used for preparative irradiation source.
Synthesis of 3-aryl-1H-inden-1-ones 1. 3-Aryl-1H-inden-1-ones 1
was synthesized according to the reported procedure.27 Typical
experiment for the Suzuki coupling reaction: a solution of the β-
bromoindenone (1.00 g, 4.8 mmol) and phenylboronic acid (0.65
g, 5.3 mmol) in THF (25 mL) containing absolute EtOH (5 mL)
and H2O (5 mL) was degassed with argon for 20 min.
Na2CO3 (1.27 g, 12 mmol) and Pd(PPh3)4 (0.23 g, 0.2 mmol) were
added to this solution. The resulting mixture was vigorously
stirred at r.t. for 1.5 d under an argon atmosphere and then diluted
with CH2Cl2 (50 mL). The reaction mixture was washed with H2O
(2 × 30 mL) and the aqueous layer extracted with CH2Cl2 (30
mL). The combined organic layers were dried over MgSO4 and
filtered. The solvent was removed in vacuo and the residue was
purified by flash column chromatography on silica gel (eluent:
toluene/hexane) to give the 3-pheylindenone 1a as a yellow solid.
Indenones (1a, 1b, 1c, and 1d) were previously reported com-
3-(p-Chlorophenyl)-1H-inden-1-one (1e). Compound 1e was pre-
pared according to the general procedure from β-bromoindenone
and p-chlorophenylboronic acid to yield the title compound as a
yellow solid (0.83 g, 3.5 mmol, 72%). The crude product was
recrystallized from a mixed solvent of CHCl3 and hexane. M.p.
1
140-141 °C; H NMR (CDCl3) δ 6.00 (s, 1H), 7.31-7.43 (m, 3H),
7.48-7.59 (m, 3H), 7.60-7.62 (m, 2H); 13C{1H} NMR (CDCl3) δ
121.4, 122,9, 123.2, 128.7, 129.3, 129.5, 131.4, 132.1, 133.0,
136.5, 143.6, 161.5, 196.8; IR (cm-1, KBr) 1711; EI-MS: m/z (rel.
intensity) 240 (M+, 83) ; HRMS (ESI-Orbitrap) m/z: [M+H]+
Calcd for C15H10ClO 241.0415; found 241.0407.
3-(p-(Trifluoromethyl)phenyl)-1H-inden-1-one (1f). Compound 1f
was prepared according to the general procedure from β-
bromoindenone and p-(Trifluoromethyl)phenylboronic acid to
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yield the title compound as a yellow solid (0.91 g, 3.3 mmol,
69%). The crude product was recrystallized from a mixed solvent
of CHCl3 and hexane. M.p. 76-77 °C; 1H NMR (CDCl3) δ 6.06 (s,
1H), 7.30-7.43 (m, 3H), 7.56 (d, J = 7.6 Hz, 1H), 7.78 (s, 4H);
13C{1H} NMR (CDCl3) δ 121.3, 123.1, 123.7 (q, J = 272 Hz),
124.2, 125.95 (q, J = 3.6 Hz), 127.7, 129.6, 131.9, 132.1 (q, J =
33 Hz), 133.2, 136.5, 143.5, 161.1, 196.6; IR (cm-1, KBr) 1713;
EI-MS: m/z (rel. intensity) 274 (M+, 66); HRMS (ESI-Orbitrap)
m/z: [M+H]+ Calcd for C16H10F3O 275.0678; found 275.0670.
of 1d. The crude product was recrystallized from a mixed solvent
of CHCl3 and hexane. M.p. 163-164 °C; H NMR (CDCl3) δ 3.61
1
1
2
3
4
5
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8
(s, 2H), 6.94 (t, J = 8.6 Hz, 4H), 7.21-7.26 (m, 4H), 7.33-7.43 (m,
6H), 7.81-7.84 (d, J =7.1 Hz, 2H); 13C{1H} NMR (CDCl3) δ 50.5,
59.8, 115.2, 115.5, 124.7, 128.9 (q, J = 8.4 Hz), 134.4, 135.2,
135.2, 137.0, 154.6, 160.0, 163.3, 202.2; IR (cm-1, KBr) 1721; EI-
MS: m/z (rel. intensity) 448 (M+, 11); HRMS (ESI-Orbitrap) m/z:
[M+Na]+ Calcd for C30H18F2O2Na 471.1167; found 471.1146.
(4bR*,4cR*,9aR*,9bR*)-4b,4c-bis(4-chlorophenyl)-4b,4c,9a,9b-
tetrahydrocyclobuta[1,2-a:4,3-a']diindene-9,10-dione (2e). Com-
pound 1e (100 mg, 0.415 mmol) was irradiated in benzene for 1 h
according to the general procedure to yield the title compound as
a colorless solid (69 mg, 0.143 mmol, 69%) with a trace amount
of 1e. The crude product was recrystallized from a mixed solvent
General procedure for the photochemical reaction of 1a-f in ben-
zene. A 0.05 M benzene solution of 1a-f (100 mg) was deaerated
by bubbling argon for 20 min, and the solution was irradiated with
a 365 nm line from a high pressure mercury lamp (500 W) for 1 h
at rt. After the solvent was removed in vacuo and the photoprod-
ucts were separated by column chromatography on silica gel,
solid dimers were recrystallized from a mixture of CHCl3-hexane.
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
1
of CHCl3 and hexane. M.p. 129-130 °C; H NMR (CDCl3) δ 3.61
(s, 2H), 7.21 (s, 8H), 7.38-7.45 (m, 6H), 7.81-7.83 (d, J = 7.6 Hz,
2H); 13C{1H} NMR (CDCl3) δ 50.4, 59.8, 124.8, 128.6, 128.6,
128.9, 129.1, 133.3, 134.5, 136.9, 137.8, 154.2, 202.0; IR (cm-1,
KBr) 1725; EI-MS: m/z (rel. intensity) 480 (M+, 52); HRMS
(ESI-Orbitrap) m/z: [M+Na]+ Calcd for C30H18Cl2O2Na
503.0576; found 503.0562.
(4bR*,4cR*,9aR*,9bR*)-4b,4c-diphenyl-4b,4c,9a,9b-
tetrahydrocyclobuta[1,2-a:4,3-a']diindene-9,10-dione (2a). Com-
pound 1a (100 mg, 0.485 mmol) was irradiated in benzene for 1 h
according to the general procedure to yield the title compound as
a colorless solid (69 mg, 0.167 mmol, 69%) accompanied with
recovered 1a (2 mg). The crude product was recrystallized from a
(4bR*,4cR*,9aR*,9bR*)-4b,4c-bis(4-(trifluoromethyl)phenyl)-
4b,4c,9a,9b-tetrahydrocyclobuta[1,2-a:4,3-a']diindene-9,10-
dione (2f). Compound 1f (100 mg, 0.364 mmol) was irradiated in
benzene for 1 h according to the general procedure to yield the
title compound as a colorless solid (67 mg, 0.122 mmol, 67%)
with a trace amount of 1f. The crude product was recrystallized
1
mixed solvent of CHCl3 and hexane. M.p. 163-164 °C; H NMR
(CDCl3) δ 3.67 (s, 2H), 7.18-7.42 (m, 16H), 7.79-7.81 (d, J = 6.4
Hz, 2H); 13C{1H} NMR (CDCl3) δ 50.3, 60.3, 124.4, 127.2,
127.2, 128.4, 128.5, 129.4, 134.1, 137.0, 139.5, 155.1, 202.8; IR
(cm-1, KBr) 1714; EI-MS: m/z (rel. intensity) 412 (M+, 10) ;
HRMS (ESI-Orbitrap) m/z: [M+H]+ Calcd for C30H21O2
413.1536; found 413.1524.
1
from a mixed solvent of CHCl3 and hexane. M.p. 144-145 °C; H
NMR (CDCl3) δ 3.69 (s, 2H), 7.37-7.43 (m, 10H), 7.53 (d, J = 8.4
Hz, 4H), 7.85 (d, J = 6.7 Hz, 2H); 13C{1H} NMR (CDCl3) δ 50.3,
60.4, 123.7 (d, J = 272.3 Hz), 125.0, 125.5 (q, J = 3.61 Hz),
127.7, 129.0, 129.2, 129.7 (d, J = 32.7 Hz), 134.6, 137.08, 143.1,
153.6, 201.6; IR (cm-1, KBr) 1724; EI-MS: m/z (rel. intensity) 548
(M+, 33); HRMS (ESI-Orbitrap) m/z: [M+Na]+ Calcd for
C32H18F6O2Na 571.1103; found 571.1082.
(4bR*,4cR*,9aR*,9bR*)-4b,4c-di-p-tolyl-4b,4c,9a,9b-
tetrahydrocyclobuta[1,2-a:4,3-a']diindene-9,10-dione
(2b).27
Compound 1b (100 mg, 0.455 mmol) was irradiated in benzene
for 1 h according to the general procedure to yield the title com-
pound as a colorless solid (59 mg, 0.134 mmol, 59%) accompa-
nied with recovered 1b (11 mg). The crude product was recrystal-
lized from a mixed solvent of CHCl3 and hexane. Reported
chemical yield was 67% using daylight. M.p. 134-135 °C; 1H
NMR (CDCl3) δ 2.26 (s, 6H), 3.62 (s, 2H), 7.03 (d, J = 8.1 Hz,
4H), 7.18 (d, J = 8.1 Hz, 2H), 7.26-7.43 (m, 6H), 7.78 (d, J = 6.8
Hz, 2H); 13C{1H} NMR (CDCl3) δ 20.9, 50.5, 59.9, 124.4, 127.1,
128.4, 129.4, 134.1, 136.7, 136.9, 136.9, 155.5, 203.0; IR (cm-1,
KBr) 1725; EI-MS: m/z (rel. intensity) 440 (M+, 31).
General procedure for the solid-state photoreaction of 1a-f. Pow-
dered chromone derivatives 1a-f (100 mg) sandwiched two Pyrex
plates in an argon purged polyethylene bag were irradiated with a
365 nm line from a 500-W high pressure mercury lamp for 1 h.
Crude photolysate was subjected to chromatography on silica gel,
and photodimers were isolated as products. Solid dimers were
recrystallized from a mixture of CHCl3-hexane.
(4bR*,4cR*,9aR*,9bR*)-4b,4c-bis(4-methoxyphenyl)-
(4bR*,4cS*,9aS*,9bR*)-4b,4c-diphenyl-4b,4c,9a,9b-
4b,4c,9a,9b-tetrahydrocyclobuta[1,2-a:4,3-a']diindene-9,10-
dione (2c).27 Compound 1c (100 mg, 0.424 mmol) was irradiated
in benzene for 1 h according to the general procedure to yield the
title compound as a orange solid (69 mg, 0.146 mmol, 69%) ac-
companied with recovered 1c (17 mg). The crude product was
recrystallized from a mixed solvent of CHCl3 and hexane. Re-
ported chemical yield was 72% using daylight. M.p. 179-180 °C;
1H NMR (CDCl3) δ 3.58(s, 2H), 3.74 (s, 6H), 6.76 (d, J = 8.8 Hz,
4H), 7.19 (d, J = 8.9 Hz, 4H), 7.34-7.38 (m, 6H), 7.79 (d, J = 7.1
Hz, 2H); 13C{1H} NMR (CDCl3) δ 50.6, 55.2, 59.5, 113.7, 124.4,
128.4, 129.3, 131.7, 134.1, 136.8, 155.6, 158.4, 203.0; IR (cm-1,
KBr) 1718; EI-MS: m/z (rel. intensity) 470 (M+, 13).
tetrahydrocyclobuta[1,2-a:4,3-a']diindene-9,10-dione (3a). Com-
pound 1a (100 mg, 0.485 mmol) was irradiated in the solid-state
for 1 h according to the general procedure to yield the title com-
pound as a colorless solid (11 mg, 0.027 mmol, 11%) accompa-
nied with 2a (21 mg, 0.051 mmol, 21%), 5a (13 mg, 0.032 mmol,
13%), and recovered 1a (19 mg). The crude product was recrys-
tallized from a mixed solvent of CHCl3 and hexane. M.p. 215-216
1
°C; H NMR (CDCl3) δ 4.02 (s, 2H), 7.11-7.18 (m, 12H), 7.36-
7.44 (m, 5H) 7.52 (d, J = 7.7 Hz, 2H); 13C{1H} NMR (CDCl3) δ
51.3, 59.8, 124.2, 126.7, 127.7, 127.9, 128.1, 128.2, 134.3, 138.5,
139.5, 155.2, 202.4; IR (cm-1, KBr) 1716; EI-MS: m/z (rel. inten-
sity) 412 (M+, 12); HRMS (ESI-Orbitrap) m/z: M+ Calcd for
C30H20O2 412.1458; found 412.1453.
(4bR*,4cR*,9aR*,9bR*)-4b,4c-bis(4-fluorophenyl)-4b,4c,9a,9b-
tetrahydrocyclobuta[1,2-a:4,3-a']diindene-9,10-dione (2d). Com-
pound 1d (100 mg, 0.446 mmol) was irradiated in benzene for 1 h
according to the general procedure to yield the title compound as
a colorless solid (94 mg, 0.210 mmol, 94%) with a trace amount
(4bR*,4cS*,9bR*,9cS*)-4b,9b-diphenyl-4b,4c,9b,9c-
tetrahydrocyclobuta[1,2-a:3,4-a']diindene-5,10-dione (5a). Col-
1
orless solid; m.p. 170-171 °C; H NMR (CDCl3) δ 4.37 (s, 2H),
7.11 (t, 2H), 7.25 (d, J = 6.8 Hz, 2H), 7.31-7.44 (m, 14H);
5
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Page 6 of 8
13C{1H} NMR (CDCl3) δ 49.7, 60.8, 123.1, 126.0, 127.0, 127.2,
(4bR*,4cS*,9aS*,9bR*)-4b,4c-bis(4-(trifluoromethyl)phenyl)-
4b,4c,9a,9b-tetrahydrocyclobuta[1,2-a:4,3-a']diindene-9,10-dione
(3f). Compound 1f (100 mg, 0.364 mmol) was irradiated in the
solid-state for 1 h according to the general procedure to yield the
title compound as a colorless solid (67 mg, 0.135 mmol, 67%)
accompanied with recovered 1f (9 mg). The crude product was
recrystallized from a mixed solvent of CHCl3 and hexane. M.p.
183-185 °C; 1H NMR (CDCl3) δ 4.02 (s, 2H), 7.21 (t, J = 6.8 Hz,
2H), 7.28 (d, J = 9.0 Hz, 5H), 7.39 (t, J = 7.7 Hz, 2H), 7.46 (t, J =
6.8 Hz, 5H), 7.55 (d, J = 7.7 Hz, 2H); 13C{1H} NMR (CDCl3) δ
51.2, 59.7, 121.9, 124.5, 125.5 (q, J = 3.73 Hz), 127.8, 128.0,
128.5, 129.3 (q, J = 32.9 Hz), 134.7, 138.5, 143.4, 153.8, 161.9,
201.2; IR (cm-1, KBr) 1726; EI-MS: m/z (rel. intensity) 548 (M+,
33); HRMS (ESI-Orbitrap) m/z: [M+Na]+ Calcd for
C32H19O2F6Na 549.1284; found 549.1293.
128.2, 129.0, 135.2, 138.2, 142.9, 155.0, 204.4; IR (cm-1, KBr)
1705; EI-MS: m/z (rel. intensity) 412 (M+, 41); HRMS (ESI-
Orbitrap) m/z: [M+H]+ Calcd for C30H21O2 413.1536; found
413.1524.
1
2
3
4
5
6
7
8
(4bR*,4cS*,9aS*,9bR*)-4b,4c-di-p-tolyl-4b,4c,9a,9b-
tetrahydrocyclobuta[1,2-a:4,3-a']diindene-9,10-dione (3b). Com-
pound 1b (100 mg, 0.455 mmol) was irradiated in the solid-state
for 1 h according to the general procedure to yield the title com-
pound as a colorless solid (13 mg, 0.030 mmol, 13%) accompa-
nied with recovered 1b (27 mg). The crude product was recrystal-
lized from a mixed solvent of CHCl3 and hexane. Colorless crys-
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
1
tal; m.p. 139-140 °C; H NMR (CDCl3) δ 2.26 (s, 6H), 3.96 (s,
2H), 6.98-7.12 (m, 10H), 7.36-7.38 (m, 4H) 7.49 (d, J = 7.7 Hz,
2H) ; 13C{1H} NMR (CDCl3) δ 21.0, 51.4, 59.4, 124.1, 127.6,
127.7, 128.0, 128.9, 134.3, 136.3, 136.6, 138.4, 155.7, 202.7; IR
(cm-1, KBr) 1719; EI-MS: m/z (rel. intensity) 440 (M+, 31);
HRMS (ESI-Orbitrap) m/z: [M+H]+ Calcd for C32H25O2
441.1849; found 441.1853.
Single crystal X-Ray structure analysis of 1b. Slightly yellow
prismatic (0.50 x 0.40 x 0.20 mm3), monoclinic space group
P21/c, a = 10.4878(12) Å, b = 10.7169(12) Å, c = 10.7804(12) Å,
β
Å,
= 101.988(2)°, V = 1185.3(2) Å3, Z = 4,
λ
(MoK
) = 0.076 cm, 6630 reflections
< 27.5126°) , nb of independ-
α) = 0.71073
ρ ꢀ (MoKα
= 1.234 g/cm3,
(4bR*,4cS*,9aS*,9bR*)-4b,4c-bis(4-methoxyphenyl)-4b,4c,9a,9b-
tetrahydrocyclobuta[1,2-a:4,3-a']diindene-9,10-dione (3c). Com-
pound 1c (100 mg, 0.424 mmol) was irradiated in the solid-state
for 1 h according to the general procedure to yield the title com-
pound as an orange solid (45 mg, 0.095 mmol, 45%) accompanied
with recovered 1c (79 mg). The crude product was recrystallized
measured (T = 173 K, 2.4655° <
θ
ent data collected: 2696, nb of independent data used for refine-
ment: 2343 in the final least-squares refinement cycles on F2, the
model converged at R1 = 0.0500, wR2 = 0.1342 [I > 2s(I)], R1 =
0.0560, wR2 = 0.1397 (all data), and GOF = 1.064, H-atom pa-
rameters constrained. (CCDC 1583299).
1
from a mixed solvent of CHCl3 and hexane. M.p. 162-163 °C; H
NMR (CDCl3) δ 3.74 (s, 6H), 3.95 (s, 2H), 6.72 (d, J = 8.8 Hz,
4H), 7.06-7.15 (m, 6H), 7.37-7.38 (m, 4H), 7.49 (d, J = 7.7 Hz,
2H); 13C{1H} NMR (CDCl3) δ 51.3, 55.2, 59.2, 113.6, 124.0,
127.7, 127.9, 128.9, 131.5, 134.3, 138.3, 155.8, 158.1, 202.6; IR
(cm-1, KBr) 2837, 1720, 1254; EI-MS: m/z (rel. intensity) 440
(M+, 7); HRMS (ESI-Orbitrap) m/z: [M+Na]+ Calcd for
C32H24O4Na 473.1747; found 473.1751.
Single crystal X-Ray structure analysis of 1c. Red prismatic (0.30
x 0.30 x 0.10 mm3), monoclinic space group C2/c, a = 41.029(4)
Å, b = 9.2510(9) Å, c = 31.065(3) Å,
9499.8(16) Å3, Z = 32,
(MoK ) = 0.71073 Å,
(MoK ) = 0.086 cm, 26697 reflections measured (T = 173 K,
2.2864° < < 23.1199°) , nb of independent data collected:
β
= 126.3240(10)°, V =
λ
α
ρ
= 1.321 g/cm3,
ꢀ
α
θ
10744, nb of independent data used for refinement: 4995 in the
final least-squares refinement cycles on F2, the model converged
at R1 = 0.0598, wR2 = 0.1374 [I > 2s(I)], R1 = 0.1419, wR2 =
0.1802 (all data), and GOF = 0.925, H-atom parameters con-
strained. (CCDC 1583300).
(4bR*,4cS*,9aS*,9bR*)-4b,4c-bis(4-fluorophenyl)-4b,4c,9a,9b-
tetrahydrocyclobuta[1,2-a:4,3-a']diindene-9,10-dione (3d). Com-
pound 1d (100 mg, 0.446 mmol) was irradiated in the solid-state
for 1 h according to the general procedure to yield the title com-
pound as a colorless solid (55 mg, 0.123 mmol, 55%) accompa-
nied with recovered 1d (35 mg). The crude product was recrystal-
lized from a mixed solvent of CHCl3 and hexane. M.p. 166-167
Single crystal X-Ray structure analysis of 1d. Slightly yellow
prismatic (0.15 x 0.10 x 0.10 mm3), monoclinic space group
1
P21/n, a = 3.8335(2) Å, b = 10.3188(4) Å, c = 26.6901(11) Å,
93.597(2)°, V = 1053.70(8) Å3, Z = 4,
(CuK ) = 1.54178 Å,
1.413 g/cm3,
(CuK
(T = 173 K, 3.3183° <
β
ρ
=
=
°C; H NMR (CDCl3) δ 3.97 (s, 2H), 6.90 (t, J = 8.6 Hz, 4H),
λ
α
7.11-7.19 (m, 6H), 7.36-7.41 (m, 4H), 7.52 (d, J = 7.7 Hz, 2H);
13C{1H} NMR (CDCl3) δ 51.2, 59.2, 115.3 (d, J = 21.6 Hz),
124.3, 127.8, 128.1, 129.4 (d, J = 7.9 Hz), 134.5, 135.1 (d, J =
3.2 Hz), 138.4, 154.8, 159.7, 163.0, 201.9; IR (cm-1, KBr) 1724;
EI-MS: m/z (rel. intensity) 448 (M+, 11); HRMS (ESI-Orbitrap)
m/z: [M+Na]+ Calcd for C30H18F2O2Na 471.1167; found
471.1155.
ꢀ
α
) = 0.819 cm, 12521 reflections measured
θ
< 68.3037°) , nb of independent data
collected: 1905, nb of independent data used for refinement: 1790
in the final least-squares refinement cycles on F2, the model con-
verged at R1 = 0.0574, wR2 = 0.1534 [I > 2s(I)], R1 = 0.0553, wR2
= 0.1555 (all data), and GOF = 1.062, H-atom parameters con-
strained. (CCDC 1583301).
(4bR*,4cS*,9aS*,9bR*)-4b,4c-Bis(4-chlorophenyl)-4b,4c,9a,9b-
tetrahydrocyclobuta[1,2-a:4,3-a']diindene-9,10-dione (3e). Com-
pound 1e (100 mg, 0.415 mmol) was irradiated in the solid-state
for 1 h according to the general procedure to yield the title com-
pound as a colorless solid (56 mg, 0.116 mmol, 56%) accompa-
nied with recovered 1e (16 mg). The crude product was recrystal-
lized from a mixed solvent of CHCl3 and hexane. M.p. 165-166
°C; H NMR (CDCl3) δ 3.95 (s, 2H), 7.08-7.21 (m, 10H), 7.34-
7.43 (m, 4H), 7.51 (d, J = 7.7 Hz, 2H); 13C{1H} NMR (CDCl3) δ
51.2, 59.3, 124.3, 127.8, 128.2, 128.7, 129.0, 132.9, 134.5, 137.9,
138.4, 154.4, 201.6; IR (cm-1, KBr) 1720; EI-MS: m/z (rel. inten-
sity) 480 (M+, 13); HRMS (ESI-Orbitrap) m/z: [M+Na]+ Calcd
for C30H19O2Cl2Na 481.0757; found 481.0762.
Single crystal X-Ray structure analysis of 1e. Slightly yellow
prismatic (0.30 x 0.20 x 0.10 mm3), monoclinic space group P21,
a = 3.8640(11) Å, b = 10.515(3) Å, c = 13.701(4) Å,
β
=
=
92.688(4)°, V = 556.1(3) Å3, Z = 2,
λ
(MoK ) = 0.71073 Å, ρ
α
1.437 g/cm3,
= 173 K, 2.4427° <
ꢀ
(MoK
α) = 0.320 cm, 3150 reflections measured (T
θ
< 23.7638°) , nb of independent data col-
lected: 1894, nb of independent data used for refinement: 1389 in
the final least-squares refinement cycles on F2, the model con-
verged at R1 = 0.0522, wR2 = 0.1085 [I > 2s(I)], R1 = 0.0794, wR2
= 0.1236 (all data), and GOF = 1.087, H-atom parameters con-
strained. (CCDC 1583303).
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Page 7 of 8
The Journal of Organic Chemistry
Single crystal X-Ray structure analysis of 2a. Colorless prismatic
(0.40 x 0.30 x 0.20 mm3), monoclinic space group P21/n, a =
86.834(2)°,
2, (MoK
cm, 13416 reflections measured (T = 173 K, 2.1721° <
23.8388°) , nb of independent data collected: 5210, nb of inde-
pendent data used for refinement: 3337 in the final least-squares
refinement cycles on F2, the model converged at R1 = 0.0540, wR2
= 0.1259 [I > 2s(I)], R1 = 0.0894, wR2 = 0.1391 (all data), and
GOF = 1.062, H-atom parameters constrained. (CCDC 1583309).
β
= 84.597(2)°,
γ
ρ
= 61.446(2)°, V = 1150.3(3) Å3, Z =
= 1.272 g/cm3,
(MoK ) = 0.078
1
2
3
4
5
6
7
8
λ
α) = 0.71073 Å,
ꢀ
α
9.9579(11) Å, b = 17.3275(19) Å, c = 12.0829(13) Å,
96.297(2)°, V = 1036.16(16) Å3, Z = 4,
(MoK ) = 0.71073 Å,
= 1.322 g/cm3,
(MoK
ured (T = 173 K, 2.3508° <
β
=
ρ
θ <
λ
α
ꢀ
α
) = 0.082 cm, 11787 reflections meas-
θ
< 27.4878°) , nb of independent
data collected: 4698, nb of independent data used for refinement:
3881 in the final least-squares refinement cycles on F2, the model
converged at R1 = 0.0401, wR2 = 0.0967 [I > 2s(I)], R1 = 0.0500,
wR2 = 0.1035 (all data), and GOF = 1.043, H-atom parameters
constrained. (CCDC 1583304).
Single crystal X-Ray structure analysis of 3d. Colorless prismatic
(0.30 x 0.30 x 0.20 mm3), monoclinic space group P21/n, a =
9
11.1685(7) Å, b = 10.7853(7) Å, c = 18.9822(11) Å,
106.1190(10)°, V = 2196.6(2) Å3, Z = 4,
(MoK ) = 0.71073 Å,
= 1.356 g/cm3,
(MoK ) = 0.095 cm, 24896 reflections meas-
ured (T = 173 K, 2.1938° < < 26.6059°) , nb of independent
β =
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
Single crystal X-Ray structure analysis of 2c. Orange prismatic
(0.30 x 0.30 x 0.30 mm3), monoclinic space group C2/c, a =
λ
α
ρ
ꢀ
α
9.019(2) Å, b = 24.900(5) Å, c = 10.765(2) Å,
2392.0(9) Å3, Z = 4,
(MoK ) = 0.71073 Å,
(MoK
2.4244° <
β
ρ
= 98.326(3)°, V =
θ
λ
α
= 1.312 g/cm3,
ꢀ
data collected: 5069, nb of independent data used for refinement:
4003 in the final least-squares refinement cycles on F2, the model
converged at R1 = 0.0399, wR2 = 0.0972 [I > 2s(I)], R1 = 0.0537,
wR2 = 0.1057 (all data), and GOF = 1.041, H-atom parameters
constrained. (CCDC 1583310).
α
) = 0.086 cm, 6823 reflections measured (T = 173 K,
θ
< 23.2245°) , nb of independent data collected: 2722,
nb of independent data used for refinement: 1901 in the final
least-squares refinement cycles on F2, the model converged at R1
= 0.0482, wR2 = 0.1197 [I > 2s(I)], R1 = 0.0726, wR2 = 0.1468 (all
data), and GOF = 1.104, H-atom parameters constrained. (CCDC
1583305).
Single crystal X-Ray structure analysis of 3e. Colorless prismatic
(0.40 x 0.40 x 0.10 mm3), triclinic space group P-1, a =
10.6655(18) Å, b = 15.265(3) Å, c = 15.421(3) Å,
71.401(2)°, = 76.345(2)°,
= 82.394(2)°, V = 2307.9(7) Å3, Z =
2, (MoK ) = 0.71073 Å, (MoK ) = 0.308
= 1.385 g/cm3,
cm, 13357 reflections measured (T = 173 K, 2.1788° <
α =
Single crystal X-Ray structure analysis of 2d. Colorless prismatic
(0.20 x 0.20 x 0.20 mm3), monoclinic space group P2/n, a =
β
γ
λ
α
ρ
ꢀ
α
15.535(3) Å, b = 7.9072(14) Å, c = 17.800(3) Å,
V = 2177.8(7) Å3, Z = 4,
(MoK ) = 0.71073 Å,
g/cm3,
(MoK ) = 0.096 cm, 12133 reflections measured (T =
173 K, 3.3284° < < 24.2568°) , nb of independent data collect-
β
= 95.106(3)°,
θ
<
λ
α
ρ
= 1.368
25.7699°) , nb of independent data collected: 10079, nb of inde-
pendent data used for refinement: 6805 in the final least-squares
refinement cycles on F2, the model converged at R1 = 0.0529, wR2
= 0.1288 [I > 2s(I)], R1 = 0.0859, wR2 = 0.1589 (all data), and
GOF = 1.052, H-atom parameters constrained. (CCDC 1583313).
ꢀ
α
θ
ed: 4969, nb of independent data used for refinement: 3430 in the
final least-squares refinement cycles on F2, the model converged
at R1 = 0.0489, wR2 = 0.1117 [I > 2s(I)], R1 = 0.0755, wR2 =
0.1337 (all data), and GOF = 1.047, H-atom parameters con-
strained. (CCDC 1583306).
Single crystal X-Ray structure analysis of 3f. Colorless prismatic
(0.40 x 0.40 x 0.40 mm3), triclinic space group P-1, a = 9.0161(9)
Å, b = 9.3663(10) Å, 16.0999(16) Å,
85.2310(10)°,
= 69.9910(10)°, V = 1248.9(2) Å3, Z = 2,
(MoK ) = 0.71073 Å,
7243 reflections measured (T = 173 K, 2.3591° <
α
= 77.8570(10)°,
β
=
Single crystal X-Ray structure analysis of 3a. Colorless prismatic
(0.50 x 0.40 x 0.20 mm3), triclinic space group P-1, a = 9.9961(9)
γ
λ
α
ρ
= 1.459 g/cm3,
ꢀ
(MoK
α
θ
) = 0.121 cm,
< 26.4905°) ,
Å, b = 10.5492(9) Å, c = 10.7931(9) Å,
65.6050(10)°, = 88.5110(10)°, V = 1036.16(16) Å3, Z = 2,
(MoK ) = 0.71073 Å,
6019 reflections measured (T = 173 K, 2.8415° <
α
= 89.0690(10)°,
β
=
λ
γ
nb of independent data collected: 5480, nb of independent data
used for refinement: 3872 in the final least-squares refinement
cycles on F2, the model converged at R1 = 0.0526, wR2 = 0.1385 [I
> 2s(I)], R1 = 0.0777, wR2 = 0.1631 (all data), and GOF = 1.051,
H-atom parameters constrained. (CCDC 1583314).
α
ρ
= 1.322 g/cm3,
ꢀ
(MoK
α) = 0.082 cm,
θ
< 27.4669°) ,
nb of independent data collected: 4544, nb of independent data
used for refinement: 3719 in the final least-squares refinement
cycles on F2, the model converged at R1 = 0.0429, wR2 = 0.1015
[I > 2s(I)], R1 = 0.0429, wR2 = 0.1108 (all data), and GOF =
1.027, H-atom parameters constrained. (CCDC 1583307).
■ ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI……. Additional experimental
procedures, X-ray crystallographic analysis, and spectroscopic
data for synthesized compounds (PDF).
Single crystal X-Ray structure analysis of 5a. Colorless prismatic
(0.50 x 0.20 x 0.20 mm3), triclinic space group P-1, a =
10.3936(12) Å, b = 13.0178(16) Å, c = 16.0441(19) Å,
α =
100.373(2)°,
= 2, (MoK
β
= 92.080(2)°,
γ
ρ
= 92.163(2)°, V = 2131.7(4) Å3, Z
■ AUTHOR INFORMATION
Corresponding Author
λ
α) = 0.71073 Å,
= 1.285 g/cm3,
ꢀ
(MoK ) = 0.079
α
cm, 12469 reflections measured (T = 173 K, 2.2250° <
θ <
21.6667°) , nb of independent data collected: 9396, nb of inde-
pendent data used for refinement: 5505 in the final least-squares
refinement cycles on F2, the model converged at R1 = 0.0585, wR2
= 0.1205 [I > 2s(I)], R1 = 0.1078, wR2 = 0.1508 (all data), and
GOF = 1.012, H-atom parameters constrained. (CCDC 1583308).
*E-mail: sakamotom@faculty.chiba-u.jp.
ORCID
Yasushi Yoshida: 0000-0002-3498-3696
Takashi Mino: 0000-0003-1588-1202
Yoshio Kasashima: 0000-0002-6224-4495
Masami Sakamoto: 0000-0001-9489-2641
NOTES
Single crystal X-Ray structure analysis of 3b. Colorless prismatic
(0.20 x 0.20 x 0.10 mm3), triclinic space group P-1, a =
10.9306(18) Å, b = 10.9660(18) Å, c = 10.9747(18) Å,
α =
7
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The authors declare no competing financial interest.
1
■ACKNOWLEDGMENT
Org. Chem. 2005, 41, 618−619.
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3
4
5
6
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This work was supported by Grants-in-Aid for Scientific Research
(Nos. 25288017, 26410124 and 16H04144) from the Ministry of
Education, Culture, Sports, Science and Technology (MEXT) of
the Japanese Government. Mr. Uemura acknowledges financial
support from Frontier Science Program of Graduate School of
Science and Engineering, Chiba University.
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McMurry, T. B. H. Synthesis 2005, 2005, 470−474.
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