Photorearrangements in spiro-conjoined cyclohexa-2,5-dien-1-one

Article abstract of DOI:10.1016/j.tet.2011.05.032

The unexpected formation of cyclohexa-2,5-dien-1-one (6) spiro-conjoined with a dihydrobenzofuran framework, and the photochemical behavior of this compound in solution as well as in the solid state are described. The photoreaction of 6 in solution afford

Full text of DOI:10.1016/j.tet.2011.05.032

Tetrahedron 67 (2011) 5500e5506
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Tetrahedron
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Photorearrangements in spiro-conjoined cyclohexa-2,5-dien-1-one
Masaya Suzuki a, Kazunori Imai a, Hidetsugu Wakabayashi a, Atsuko Arita b, Kohei Johmoto b,
,
Hidehiro Uekusa b, Keiji Kobayashi a
*
a Department of Chemistry, Graduate School of Science, Josai University, Keyakidai, Sakado, Saitama 350-0295, Japan
b Department of Chemistry and Material Science, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-8551, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
The unexpected formation of cyclohexa-2,5-dien-1-one (6) spiro-conjoined with a dihydrobenzofuran
framework, and the photochemical behavior of this compound in solution as well as in the solid state are
described. The photoreaction of 6 in solution affords two rearranged products, one (7) accompanied by
the enlargement of the oxygen heterocyclic ring and the other (8) accompanied by cyclopentadienone
fragmentation. In the solid state, the former is the sole photoproduct of both solvated and desolvated
crystals. The desolvated crystals were obtained as polycrystalline solids by thermal release of solvent
molecules, and its structure was elucidated by ab initio determination from X-ray powder diffraction
data followed by the Rietveld refinement.
Received 13 April 2011
Received in revised form 7 May 2011
Accepted 9 May 2011
Available online 14 May 2011
Keywords:
Solid-state photoreaction
Photorearrangement
Solvate crystal
Ó 2011 Elsevier Ltd. All rights reserved.
X-ray powder diffraction
Rietveld refinement
1. Introduction
latter, solvated and desolvated crystals were used to gain insight to
the comparative photoreactivity upon solid-state irradiation.
Diradicals are a focus of increasing interest because of their
importance in gaining an understanding of spinespin interactions.1
Recently, we have reported interesting dynamic behavior that in-
volves bond dissociation and regeneration via diradical species;2
the cyclopropane ring of compound 1 has been found to exist in
solution in fast equilibrium with diradicals via the dissociation of
the CeC bond of trispiro-conjoined cyclopropane. In the solid state,
on the other hand, 1 exhibits slow interconversion between ring-
opened and ring-closed forms. Thus, when heated to 180 ꢀC, 1
undergoes homolytic bond dissociation to generate a diradical,
which persists and gradually regenerates the cyclopropane ring as
temperature is decreased. This cycle of reversible bond dissociation
and recombination via a diradical is accompanied by a color change.
The diradical derived from 1 consists of two bisphenoxyl radicals in
which the fundamental framework bearing the radical centers is
bis(p-hydroxyphenyl)methane (p,p-isomer). Thus, it is interesting
to determine whether similar dynamic behavior to that observed in
the p,p-isomer occurs in o,p- and o,o-isomeric forms (Scheme 1). In
this context, we have prepared their possible precursor compounds
and investigated their photochemical and thermal properties,
particularly in the solid state. Herein, we describe unusual photo-
induced rearrangements in spiro-cyclohexadienone compound 6
occurring not only in solution but also in the solid state. For the
2. Results and discussion
2.1. Preparation of precursor for p,o-isomer
As a possible precursor for the generation of p,o-diradicals, we
chose 2-(3,5-di-tert-butyl-4-hydroxyphenyl)-2-(3,5-di-tert-butyl-
2-hydroxyphenyl)-1H-indene-1,3(2H)-dione (2), which is expected
to afford cyclopropane compound 3 by oxidation similarly to 1.
Compound 2 was prepared by the reactions of ninhydrin with 2,6-
di-tert-butylphenol and then with 2,4-di-tert-butylphenol. The
product actually has an intramolecular hemiacetal structure, 4,
rather than the expected dihydroxyphenyl structure.3 Compound 4
was oxidized by potassium hexacyanoferrate(III) in a similar re-
action to that for 1. The product, however, was not the cyclopropane
compound 3, but the ring-expanded lactone 5 (52%) and the spiro-
conjoined cyclohexa-2,5-dien-1-one 6 (24%) (Scheme 2). The oxida-
tion of (p-hydroxyphenyl)(o-hydroxyphenyl)methane compounds
has been known to frequently afford spiro-cyclohexadienone
compounds.4 Therefore, 4 is assumed to exist in equilibrium with
the ring-opened form, which could be oxidized to afford 6.
The structures of 5 and 6 were elucidated by 1H NMR and mass
spectrometry and confirmed by X-ray analysis (Figs. 1 and 2). The
quinonoid compound 5, an orange solid, exhibits two sets of two
doublets weakly coupled to each other and four methyl signals due
* Corresponding author. E-mail address: kobayak@josai.ac.jp (K. Kobayashi).
0040-4020/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2011.05.032

M. Suzuki et al. / Tetrahedron 67 (2011) 5500e5506
t-Bu
5501
t-Bu
t-Bu
O
O
O
t-Bu
O
O
t-Bu
t-Bu
O
t-Bu
O
O
t-Bu
t-Bu
O
t-Bu
t-Bu
O
O
O
O
O
t-Bu
O
t-Bu
O
t-Bu
t-Bu
t-Bu
1
p-, o-
p-, p-
o-, o-
Scheme 1. Isomeric diradicals based on bis(hydroxyphenyl)methane.
t-Bu
O
t-Bu
O
t-Bu
O
OH
t-Bu
t-Bu
t-Bu
t-Bu
K3[Fe(CN)6]
O
t-Bu
t-Bu
O
O
+
O
O
HO
O
O
t-Bu
t-Bu
t-Bu
4
5
6
O
t-Bu
OH
t-Bu
t-Bu
t-Bu
O
O
t-Bu
O
OH
O
t-Bu
O
t-Bu
t-Bu
3
2
Scheme 2. Oxidation of 4.
Fig. 2. X-ray structure of acetonitrile solvate crystal of 6.
to the tert-butyl groups along with multiplets for four aromatic
protons. In the X-ray crystallographic analysis, appreciable thermal
motion in the tert-butyl groups of the benzene ring was observed,
however, the results clearly indicate the structure of 5. The eight-
membered ring is distorted into a tub structure with an O]
C/C]C torsional angle of 49.54ꢀ. On the other hand, the dihedral
angle of C(Ph)eC(]O)/OeC(Ph) is 10.63ꢀ.
Fig. 1. X-ray structure of 5.

5502
M. Suzuki et al. / Tetrahedron 67 (2011) 5500e5506
Single crystals of 6 suitable for X-ray studies were obtained by
On the other hand, the separation of 6 and 7 could neither be
achieved by GPC even after 10 cycles nor by recrystallization from
various solvents. The structure of 7 was elucidated on the basis of
the spectral data from a sample in which 6 and 7 coexist. The mass
spectrum of this sample was not distinguishable from that of pure
6, indicating that the concomitant photoproduct is an isomer of 6.
In Fig. 4, the 1H NMR spectrum of the sample is shown, for which
the signals attributed to 7 are indicated by asterisks. The 1H signal
at 2.98 ppm, which is assigned to the methine proton, is weakly
coupled to the signal at 7.06 ppm (J¼3.6 Hz), indicating the pres-
ence of the CHeCH]C framework. In 13C NMR, at least 28 signals
are assigned to photoproduct 7 by eliminating 21 signals due to 6.
These include the signals due to three carbonyl carbons (202.0,
200.0 and 192.9 ppm) and the quart- and tert-carbons at the spiro-
conjoined positions (63.9 and 50.8 ppm, respectively). In the IR
spectrum, an OH stretching band was not observed. On the basis of
these results, the structure of the photoproduct was determined to
be 7, which includes the partial structure of the keto form of
a phenol. It is rather surprising that 7 fails to undergo enolization by
treatment with acid, although there have been many examples of
such rearrangements that are known as cyclohexadienoneephenol
rearrangements.6
A plausible mechanism of the photorearrangement of 6 to 7
involves the homolytic cleavage of the CeO bond of the five-
membered oxygen ring to form the p-,o-diradical isomer shown
in Scheme 1. The recombination of the diradical to furnish the six-
membered ring followed by hydrogen migration results in the
formation of 7. The carboneoxygen bond linked to the 4-position of
cyclohexa-2,5-dien-1-one has been known to undergo direct pho-
tochemical cleavage.7 Alternatively, as observed in the photo-
chemistry of 2,4,6-tri-tert-butyl-4-methoxy-cyclohexadienones,8
the slow evaporation of the solvent from acetonitrile solution.
X-ray analysis revealed that the crystals are solvated by MeCN
molecules in a ratio of 6/MeCN¼1:1. These solvent molecules are
embedded in a channel-like column and not released after five days
at room temperature. The 1H NMR spectrum of 6 at room tem-
perature and even at high temperatures showed no evidence that
dynamic molecular motion occurs in 6. When 6 was heated to
above its melting point (234 ꢀC), no decomposition was observed.
We carried out a photoreaction of 6, expecting to find a photore-
action via the p,o-isomeric bis(phenoxyl) radical, which would be
formed if the single bond connecting the spiro carbon and oxygen
atoms undergoes hemolytic bond cleavage.
2.2. Photolysis in solution
An acetonitrile solution of compound 6 (ca. 1.2 mmol/L) was
irradiated with a high-pressure mercury lamp through a Pyrex
filter under nitrogen at room temperature. Distinct photoreac-
tions were induced as probed by the 1H NMR analysis of the re-
action mixture, which clearly shows two photoproducts, i.e., 7
and 8, along with starting compound 6 in a ratio of 7/8/6¼1:2:3
(Scheme 3). The photoproduct 8 was isolated by gel permeation
chromatography (GPC) and its structure was elucidated by NMR
and mass spectrometry. The 1H NMR spectrum exhibited a set of
AA0BB0 signals in the aromatic region due to four protons and two
slightly coupled doublets a 1,2,3,5-tetra-substituted benzene ring.
The chemical shifts of these latter signals are in fair agreement
with those reported for a similar benzoquinone-fused benzofuran
derivative.5 Eventually, the structure of 8 was confirmed by X-ray
analysis. Although the results are not good enough to provide
accurate structural parameters because of the poor crystallinity of
the single crystal employed for data collection, they are still sat-
isfactory for revealing the gross structure of 8 (Fig. 3).
the photoexcited transformation to
a bicyclo[3.1.0]hexanone
framework would be involved.9 This latter mechanism also ac-
counts for the formation of 8 as shown in Scheme 4. Thus, the
O
t-Bu
O
t-Bu
t-Bu
O
O
O
t-Bu
H
O
t-Bu
hv
O
+
O
CH3CN
O
O
O
t-Bu
t-Bu
t-Bu
t-Bu
t-Bu
6
7
8
Scheme 3. Photoreaction of 6.
formation of 8 could be rationalized analogously to the photore-
action of 4-tert-butylperoxy-4-methyl-2,6-di-tert-butylcyclohex-
adienone, wherein 1,5-di-tert-butylcyclopentadienone is formed
via a lumiketone-type intermediate followed by radical rear-
rangement.10 Such a photoprocess for 6 would result in the elimi-
nation of the 2,5-di-tert-butycyclopentadienone fragment. In the
mass spectra of the photoreaction mixture, the molecular ion
peak assignable to 2,5-di-tert-butycyclopentadienone was detected
at m/z¼191.
2.3. Photolysis in the solid state
Upon recrystallization from acetonitrile, 6 was obtained as sol-
vate crystals including 6/CH3CN in a 1:1 ratio. The polycrystalline
solid of 6 was held among Pyrex plates and irradiated with a mer-
cury lamp at room temperature. After 3 h, the solid was dissolved in
CDCl3 and its NMR spectrum was recorded, which showed the
Fig. 3. X-ray structure of 8.

M. Suzuki et al. / Tetrahedron 67 (2011) 5500e5506
5503
*
Fig. 4. NMR spectrum (in CD3CN) of photoproduct 7 coexisting with 6. Signals due to 7 are indicated by asterisks ( ). The methyl protons of tert-butyl groups are outside this scale.
O
t-Bu
t-Bu
O
O
O
t-Bu
O
t-Bu
t-Bu
O
t-Bu
t-Bu
H
O
7
O
O
t-Bu
O
O
O
t-Bu
t-Bu
t-Bu
t-Bu
6
t-Bu
O
O
t-Bu
O
*
t-Bu
H
t-Bu
t-Bu
O
H
O
O
t-Bu
O
O
t-Bu
lumi-ketone
t-Bu
O
t-Bu
H
t-Bu
t-Bu
O
H
O
O
+
t-Bu
t-Bu
8
H
H
O
t-Bu
Scheme 4. Plausible reaction paths to 7 and 8.
existence of 7 as the sole product with a 15% yield: the other
compound 8 obtained in solution photochemistry was not detec-
ted. The distinct photochemical behavior in the solid state from that
in solution suggests that the lattice-controlled reaction is induced
in the solid state.11 The solvate acetonitrile was retained in the
photoproduct after photoirradiation, as observed in the NMR
spectrum.12 XRD studies revealed the occurrence of haloes in the
XRD profiles after photoirradiation (Fig. 5). This observation in-
dicates that the solid-state reaction results in the collapse of the
crystalline phase to form an amorphous phase in ca. 15% of the
entire solid. This was also the case for photoirradiation of single
crystals of 6, although the conversion of 6 to 7 was as low as 5% after
48 h irradiation.
Single crystals of 6 became opaque when acetonitrile was re-
leased by heating to 80 ꢀC. It was revealed on the basis of the XRD
studies that the resulting solids were in a new crystalline phase
(Fig. 5). Then, in order to examine the effect of crystal environment
on the reaction, the solid-state photoreaction of desolvated 6 was
also carried out. The result was the formation of 7 as a single
product in ca. 10% yield after 40 h irradiation. The XRD profiles after
photoirradiation again exhibited haloes. The conversion of 6 to 7
should be accompanied by an appreciable structural change that
disturbs the crystalline environment around the reaction sites. A
mismatching between the reactant and product in terms of mo-
lecular structure would induce a collapse to the amorphous phase
at reaction sites.12
We were able to elucidate the crystal structure of desolvated
crystals of 6 by ab initio structure determination from X-ray powder
diffraction data followed by the Rietveld refinement, which entails
refining the parameters of a structural model to supply a calculated
X-ray powder diffraction pattern similar to the observed one.13
Fig. 5(d) shows the Rietveld refinement plot for desolvated crystals
of 6. The molecular packing is similar before and after the loss of
acetonitrile in the sense that the molecules are aligned along the b-
axis (Fig. 6), although the space group changes from P-1 to P21. It is
interesting to note that achiral solvate crystals are transformed into
chiral crystals by elimination of solvent molecules; the molecules of
6 are in a chiral structure because of deformation of the five-

5504
M. Suzuki et al. / Tetrahedron 67 (2011) 5500e5506
Fig. 6. Crystal structures of (a) (6)(CH3CN) and (b) desolvated 6.
there are no appreciable differences in the reaction rate. It might be
assumed, at least from this observation, that degradation of the
crystalline state into an amorphous phase does not play a role in
controlling the rate.
2.4. Attempted preparation of precursor of o-,o-isomer
In our attempts to synthesize the o-,o-diradical isomer, as rep-
resented in Scheme 1, 2,2-(3,5-di-tert-butyl-2-hydroxyphenyl)-1H-
indene-1,3(2H)-dione (9) was chosen as the appropriate precursor.
To prepare 9, ninhydrin was reacted with 2,4-di-tert-butylphenol in
acetic acid in the presence of a small amount of sulfuric acid.
Contrary to our expectation, the product was the benzofurane-
condensed lactone 10 (20%). Although the reactions of ninhydrin
with p-substituted phenols in the presence of ZnCl2 have been
reported to give this type of lactone,14 their structural character-
ization is unequivocal. We carried out an X-ray analysis of a single
crystal obtained by recrystallization from benzene and un-
ambiguously determined the structure of the product (Fig. 7). The
crystal of 10 includes benzene molecules located in a channel
running along the a-axis. The eight-membered ring has a tub
structure angle of 10.63ꢀ for CeOeC(O)eC.
Fig. 5. XRD profiles of 6. (a) Solvate crystal of 6$CH3CN after photoirradiation, (b)
solvated crystal of 6$CH3CN before photoirradiation, (c) desolvated solids of 6 obtained
after heating, and (d) Rietveld refinement plot for desolvated 6.
Fig. 7. X-ray structure of 10. Solvated benzene molecules are omitted for clarity.
membered oxygen heterocycle from a planar geometry. With the
crystal structures of solvated and desolvated 6 in hand, we carried
out a comparative investigation of their photoreactivity, considering
that solid state reactions under lattice control depend on the crys-
talline environment. The photoreactions were monitored by exam-
ining the decrease in IR absorbance at 1714 and 1647 cmꢁ1 upon the
irradiation of the sample compressed in KBr pellets. However, the
results were not in agreement with our expectation, indicating that
A plausible mechanism of the formation of 10 is shown in
Scheme 5 and is based on analogous systems.15 Cleavage at the
carbonecarbon bond of the intramolecular hemiacetal structure
produces an eight-membered lactone ring, and acid-catalyzed
hemiacetal formation at the carbonyl unit leads to the formation
of a furan ring. In spite of all our efforts including the use of milder
reaction conditions, we could not isolate a hemiacetal intermediate.

M. Suzuki et al. / Tetrahedron 67 (2011) 5500e5506
5505
OH
t-Bu
t-Bu
O
t-Bu
HO
O
t-Bu
t-Bu
HO
O
O
O
t-Bu
t-Bu
t-Bu
OH
OH
t-Bu
t-Bu
t-Bu
OH
H SO
O
2
4
HO
O
O
+
H
HO
CH COOH
3
t-Bu
O
t-Bu
t-Bu
10
9
Scheme 5. Plausible reaction path to 10.
3. Conclusions
136.10, 137.82, 142.81, 151.89, 152.04, 152.86, 201.59. MS (m/z): 554
(Mþ), 539, 498. Anal. Calcd for C37H46O4: C, 80.11; H, 8.36%. Found:
C, 79.08; H, 8.14%.
We have observed the unexpected formation of a novel cyclo-
hexadienone compound incorporated in the dispiro framework
upon the oxidation of intramolecular hemiacetal compounds. The
photoirradiation of this compound in acetonitrile induced a rear-
rangement, resulting in the expansion of the oxygen heterocyclic
ring, leaving the cyclohexadienone moiety intact. Another photo-
product was accompanied by the fragmentation of the cyclo-
pentadienone skeleton to afford benzofuranonaphthoquinone.
Photoirradiation in the solid state afforded only the former as
a product of solvated crystals as well as of desolvated crystals, for
which the crystal structure was determined by powder X-ray dif-
fraction. In both solvated and desolvated crystals, the photoreaction
induced an amorphous phase at the reacted sites.
4.1.2. Oxidation of 4. To
a
solution of potassium hex-
acyanoferrate(III) (3.5 g) and sodium hydroxide (0.8 g) in 15 mL
water was added 4 (1.0 g, 1.8 mmol) dissolved in CHCl3 (50 mL) at
25 ꢀC. The mixture was stirred for 1 h. After aqueous work up, ex-
traction with chloroform (300 mL), drying over anhydrous Mg2SO4,
and evaporation of the solvent under reduced pressure, the residual
solid was chromatographed on silica gel with benzene and
dichloromethane as eluents to give 5 (0.52 g, 52%) and 6 (0.24 g,
24%).
4.1.2.1. 2,4-Di-tert-butyl-12-(3,5-di-tert-butyl-4-oxo-2,5-
cyclohexadienylidene)-11,12-dihydro-6H-dibenzo[b.f]oxocin-6,11-
dione (5). Reddish brown crystals. Mp 207e209 ꢀC. IR (Nujol): 1747,
1664, 1624 cmꢁ1
(1H, d, J¼2.4 Hz), 7.43 (1H, d, J¼2.6 Hz), 7.51 (1H, d, J¼2.3 Hz), 7.53
(1H, m), 7.66 (2H, m), 7.80 (1H, m). MS (m/z): 552 (Mþ). Anal. Calcd
for C37H44O4: C, 80.45; H, 7.97%. Found: C, 80.08; H, 8.11%.
.
1H NMR (CD3CN):
d
6.63 (1H, d, J¼2.6 Hz), 7.15
4. Experimental
4.1. General
All melting points were determined using a Yanaco MS-500 V
apparatus and are uncorrected. The IR spectra were obtained on
a Shimadzu FTIR-8200PC spectrometer. The 1H NMR (500 MHz)
4.1.2.2. 3,5,50,70-Tetra-tert-butyldispiro[[2,5]cyclohexadiene-1,20-
[2,3]dihydrobenzofuran-30,200-[2H]indene]-100,300,4-trione ꢁ(16). Yellow
and 13C NMR (125 MHz) spectra were recorded using a JEOL
a
-500
crystals. Mp 234 ꢀC. IR (Nujol): 1714, 1672, 1647 cm
.
1H NMR
spectrometer. Chemical shifts are given in
d values (ppm) using
(CDCl3):
d 1.04 (18H, s), 1.25 (9H, s), 1.43 (9H, s), 6.65 (1H, d,
TMS as the internal standard. Mass spectra were taken on a Shi-
madzu GCeMS-QP5050A mass spectrometer. Elementary com-
bustion analyses were recorded using a Yanaco CHN CORDER MT-6
analyzer. All reactions were monitored by TCL employing
a 0.25 mm silica gel plate (Merck 60F 254). Gel permeation chro-
matography (GPC) was performed using two columns (GAIGEL 1H
and 2H) on an LC-908 recycling preparative HPLC. Column chro-
matography was carried out on silica gel (Merck 60N spherical).
J¼1.8 Hz), 6.75 (2H, s), 7.31 (1H, d, J¼1.8 Hz), 7.84 (2H, dd, J¼3.1,
3.1 Hz), 7.93 (2H, dd, J¼3.1, 3.1 Hz). 13C NMR (CDCl3):
d 28.95, 29.32,
31.66, 34.46, 34.62, 34.82, 73.77, 85.57, 119.24, 123.59, 124.60,
124.82, 133.38, 136.18, 137.44, 142.86, 144.60, 147.56, 156.43, 185.34,
196.90. MS (m/z): 552 (Mþ). Anal. Calcd for C37H44O4: C, 80.45; H,
7.97%. Found: C, 80.56; H, 8.24%.
4.2. Photoreaction of 6
4.1.1. Preparation of 2-(3,5-di-tert-butyl-4-hydroxyphenyl)-2-(3,5-
di-tert-butyl-2-hydroxyphenyl)-1H-indene-1,3(2H)-dione (4). To
a
An acetonitrile solution of compound 6 (1.2 mmol/L) was irra-
diated with a high-pressure Hg lamp (Riko UVL-400HA) through
a Pyrex filter under nitrogen at 0 ꢀC. After irradiation for 1 h the
solvent was removed under reduced pressure without heating. The
resulting residue was chromatographed on GPC (JAL-gel, GPL) to
afford two fractions; one, a mixture of 6 and 7, and the other, 8. The
percent conversion was determined by NMR of the crude reaction
mixture after evaporation.
Solid-state irradiation was carried out for samples (ca. 25 mg)
held between Pyrex glasses or dispersed in compressed KBr pellets
under atmospheric environment at room temperature. The irradi-
ated solids were dissolved in CDCl3 for analysis by NMR. The IR
spectra were obtained from KBr pellets on a BioRad FTS-3000 FT-IR
spectrophotometer.
solution of 2-hydroxy-2-(3,5-di-tert-butyl-4-hydroxyphenyl)-1H-
indene-1,3(2H)-dione (3.0 g, 8.2 mmol) in acetic acid (30 mL) were
added a small amount of p-toluenesulfonic acid (ca. 10 mg) and 2,4-
di-tert-butylphenol (2.0 g, 9.8 mmol) at room temperature. The
mixture was heated at reflux for 4 h. Aqueous work up, extraction
with dichloromethane, and drying over anhydrous Mg2SO4 affor-
ded a reddish solution. After the solvent was removed under re-
duced pressure, the resulting solids were washed with hexane for
decoloration and recrystallized from acetonitrile to give 4 (4.2 g,
92%) as a white solid.
Compound 4: Mp 268e269 ꢀC. IR (Nujol): 3630, 3298,
1701 cmꢁ1. 1H NMR (CDCl3):
d 1.24 (9H, s), 1.32 (18H, s), 1.37 (9H, s),
3.05 (1H, br s), 5.27 (1H, br s), 6.73 (2H, s), 7.20 (1H, d, J¼2.4 Hz),
7.21 (1H, J¼2.4 Hz), 7.55 (1H, t, J¼7.2 Hz), 7.77 (1H, J¼7.0 Hz), 7.87
(1H, d, J¼7.6 Hz), 8.00 (1H, d, J¼7.9 Hz). C13 NMR (DMSO-d6):
4.2.1. 20,40,50,70-Tetra-tert-butyl-3-hydroxy-spiro[[2H]indene-2,90-
[9H]xanthene]-1,3-dione (7)dketo form. By subtracting the signals
due to 6 in 1H and 13C NMR spectra the following signals are
d
29.06, 29.20, 30.23, 31.52, 33.98, 34.22, 34.96, 68.97, 69.30, 113.03,
120.17, 122.77, 124.56, 125.85, 126.01, 127.80, 130.54, 131.53, 134.80,

5506
M. Suzuki et al. / Tetrahedron 67 (2011) 5500e5506
assignable to 7. 1H NMR (CD3CN):
d
0.49 (9H, s), 1.02 (9H, s), 1.08
temperature on beamline 4B2 (parallel beam optics) at the PF
synchrotron facility using a wavelength of 1.197040(7) A. The
ꢀ
(9H, s), 1.40 (9H, s), 2.98 (1H, d, J¼3.6 Hz), 6.24 (1H, d, J¼1.9 Hz),
7.06 (1H, d, J¼3.6 Hz), 7.26 (1H, d, J¼1.9 Hz), 8.00 (4H, m). 13C NMR
sample was loaded into a borosilicate glass capillary (2.0 mm di-
ameter) and was used for the diffraction measurement in trans-
mission mode. The powder X-ray diffraction pattern was indexed
using the program DICVOL04.17 The structure solution was carried
out using the simulated annealing method incorporated in the
program DASH.18 The best structure obtained in the structure so-
lution calculation was used as the initial structural model for
Rietveld refinement, which was carried out using the GSAS
program.19
(CDCl3): d 202.0, 200.0, 192.9, 154.5, 153.5, 151.2, 144.6, 143.0, 140.8,
136.7, 135.8, 132.4, 125.2, 124.1, 123.5, 115.6, 63.9, 50.8, 34.4, 34.2,
32.5, 32.1, 29.3, 28.7, 27.4, 26.2. Anal. Calcd for C37H44O4: C, 80.45;
H, 7.97%. Found: C, 80.72; H, 7.88%.
4.2.2. 2,4-Di-tert-butylbenzo[b]naphtho[2,3-d]furan-6,11-dione
(8). 1H NMR (CD3CN):
d 1.51 (9H, s), 1.43 (9H, s), 7.64 (1H, d,
J¼2.1 Hz), 7.84 (2H, m), 8.10 (1H, d, J¼2.1 Hz), 8.18 (2H, m). 13C NMR
(CDCl3):
d 29.96, 31.69, 34.75, 35.26, 117.47, 123.14, 124.27, 124.50,
126.64, 126.81, 132.61, 133.40, 133.72, 133.95, 135.70, 149.53, 153.20,
153.47, 175.25, 181.88. MS (m/z): 360 (Mþ), 344. Anal. Calcd for
C24H24O3: C, 80.00; H, 6.67%. Found: C, 80.26; H, 6.29%.
4.5.1. Crystal data for 6. C37H44O4, P21 (#4), monoclinic,
¼102.5746(1)ꢀ,
Rp¼0.0215,
ꢀ
a¼10.3569(3), b¼16.5705(4), c¼9.7932(4) A,
b
3
ꢀ
V¼1640.39(10) A ,
Z¼2,
Dcalcd¼1.119 g/cm3,
Rwp¼0.0287, CCDC 818653.
4.3. Reaction of ninhydrin with 2,4-di-tert-butylphenol
To a solution of ninhydrin (3.02 g, 17 mmol) in acetic acid
(30 mL) were added 2,4-di-tert-butylphenol (6.97 g, 34 mmol) and
a drop of concd sulfuric acid. The mixture was heated at reflux for
4 h. Aqueous work up, extraction with dichloromethane (300 mL),
and drying over anhydrous Mg2SO4 afforded a reddish solution.
After the solvent was removed under reduced pressure, the
resulting solids were chromatographed on silica gel with benzene
as eluent to give 10 (1.82 g, 20%).
Acknowledgements
This work was supported by Grants-in-Aid for Scientific Re-
search (C) from MEXT (Nos. 21550048 and 21550008). Part of this
work was performed under the approval of the Photon Factory
Program Advisory Committee (Proposal No. 2009G658).
References and notes
4.3.1. 2,4,12,14-Tetra-tert-butyl-6H-dibenzo[b.f]benzofuro[3,2-d]ox-
ocin-6-one (10). Mp 216e217 ꢀC. IR (Nujol): 1732, 1248 cmꢁ1 1H
.
1. (a) Diradicals; Borden, W. T., Ed.; Wiley: New York, NY, 1982; (b) Rajca, A. Chem.
Rev. 1994, 94, 871; (c) Adam, W.; van Barneld, C.; Emmert, O.; Harrer, H. M.;
Kita, F.; Kumar, A. S.; Maas, W.; Nau, W. M.; Reddy, S. H. K.; Wirz, J. Pure Appl.
Chem. 1997, 69, 735.
2. Kiyohara, S.; Ishizuka, K.; Wakabayashi, H.; Miyamae, H.; Kanazumi, M.; Kato,
T.; Kobayashi, K. Tetrahedron Lett. 2007, 48, 6877.
NMR (CDCl3):
d
6.61 (1H, d, J¼1.8 Hz), 6.80 (1H, q, J¼1.5 Hz), 6.87
(1H, d, J¼3.1 Hz), 7.28 (1H, J¼1.8 Hz), 7.89 (4H, m). MS (m/z): 536
(Mþ). Anal. Calcd for C37H44O3 :C, 82.78; H, 8.18%. Found: C, 82.26;
H, 8.04%.
3. (a) Hashimoto, S.; Sakuma, N,; Wakabayashi, H.; Miyamae, H.; Kobayashi, K.
Chem. Lett. 2008, 37, 696; (b) Das, S.; Frohlich, R.; Pramanik, A. A. Org. Lett.
2006, 8, 4263; (c) Na, J. E.; Lee, K. Y.; Seo, J.; Kim, J. N. Tetrahedron Lett. 2005,
46, 4505.
4. (a) Tsuge, O.; Watanabe, H.; Kanemasa, S. Chem. Lett. 1984, 1415; (b) Dean, F. M.;
Herbin, G. A.; Matkin, D. A.; Price, A. W.; Robinson, M. L. J. Chem. Soc. Perkin
Trans. 1 1980, 1986; (c) Bennett, D. J.; Dean, F. M.; Herbin, G. A.; Matkin, D. A.;
Price, A. W.; Robinson, M. L. J. Chem. Soc., Perkin Trans. 1 1980, 1978; (d) Feringa,
B.; Wynberg, H. Tetrahedron Lett 1977, 447; (e) Katoh, T.; Ohmori, O.; Iwasaki,
K.; Inoue, M. Tetrahedron 2002, 58, 1289.
5. Tashiro, M.; Yoshiya, H.; Fukata, G. J. Org. Chem. 1981, 46, 3784.
6. Frimer, A. A.; Marks, V.; Sprecher, M.; Gilinsky-Sharon, P. J. Org. Chem. 1994, 59,
1831 and references cited there.
7. (a) Taub, D.; Kuo, C. H.; Slates, H. L.; Wender, N. L. Tetrahedron 1963, 19, 1; (b)
Hewgill, F. R.; Raston, C. L.; Skelton, B. W.; Webb, R. J.; White, A. H. Aust. J. Chem.
1983, 36, 1603.
8. (a) Matsuura, T.; Ogura, K. J. Am. Chem. Soc. 1967, 89, 3846; (b) Matsuura, T.;
Meng, J.-B.; Ito, Y.; Irie, M.; Fukuyama, K. Tetrahedron 1987, 43, 2451.
9. (a) Schaffner, K.; Demuth, M. In Rearrangements in Ground and Excited States;
de Mayo, P., Ed.; Academic: New York, NY, 1980; Vol. 3, pp 281e348; (b)
Schultz, A. G. Pure Appl. Chem. 1988, 60, 981; (c) Schuster, D. I. Acc. Chem. Res.
1978, 11, 65.
10. (a) Lind, H.; Winkler, T.; Loeliger, H. J. Polym. Sci. Part C, 1976, 57, 225; (b)
Zimmerman, H. E.; Keese, R.; Nasielski, J.; Sweton, J. S. J. Am. Chem. Soc. 1966,
88, 4895.
4.4. Single-crystal X-ray crystallography
X-ray crystallographic data were collected at cryogenic tem-
perature (ꢁ50 ꢀC) for 6 and at ambient temperature for others on
a Rigaku-RAPID imaging plate two-dimensional area detector using
ꢀ
graphite monochromatized Mo K
a
radiation(
l
¼0.71073 A). All
crystallographic calculations were performed using Crystal-
Structure crystallographic software.16 Crystal data have been sub-
mitted to CCDC, which can be obtained free of charge at
www.ccdc.cam.ac.uk/conts/retrieving.html.
4.4.1. Crystal data for 5. C37H44O4, P-21/c (#14), a¼9.4641(9),
3
ꢀ
ꢀ
ꢀ
b¼24.3590(20), c¼14.6422(11) A,
b
¼104.825(3) , V¼3263.2(5) A ,
Z¼4, Dcalcd¼1.125 g/cm3, R1¼0.1241, wR2¼0.3521, CCDC 813921.
Crystal data for (6)(CH3CN): C39H47O4N, P-1 (#2), a¼9.7554(5),
¼85.6750(15)ꢀ,
ꢀ
b¼12.5742(5), c¼14.6696(8) A,
a
b
¼77.3860(15)ꢀ,
3
g
¼82.0220(14) , V¼1737.13(14) A , Z¼2, Dcalcd¼1.135 g/cm3, R1¼0.0467,
ꢀ
ꢀ
wR2¼0.1520, CCDC 813922. Crystal data for 8. C24H24O3, Pnma (#62),
3
ꢀ
ꢀ
a¼15.1070(13), b¼7.1473(5), c¼18.1696(14) A, V¼1961.9(3) A , Z¼4,
11. The NMR analysis could not reveal if acetonitrile molecules were retained in the
amorphous region where the reactions took place. It would be reasonable to
assume that the solvate has been lost in such a region.
12. Paul, I. C.; Curtin, D. Y. Acc. Chem. Res. 1973, 6, 217.
13. Rietveld, H. M. J. Appl. Crystallogr. 1969, 2, 65.
Dcalcd¼1.220 g/cm3, R1¼0.1231, wR2¼0.1924. CCDC 813923.Crystal
data for (10)2(benzene)3: C46H53O3, P-1 (#2), a¼9.57324(5),
¼66.0570(9)ꢀ,
ꢀ
b¼15.2267(7), c¼15.2332(7) A,
a
b
¼77.3180(15)ꢀ,
3
ꢀ
14. Roussey, J.-C.; Laude, B. C. R. Acad. Sci. Ser. C, 1979, 288, 225.
15. Das, S.; Frohlich, R.; Pramanik, A. Synlett 2006, 207.
g
¼84.2820(16)ꢀ, V¼1979.83(16) A , Z¼2, Dcalcd¼1.097 g/cm3,
R1¼0.1097, wR2¼0.2720, CCDC 813924.
16. CrystalStructure, Ver.3. 7; Rigaku Corporation: Tokyo, 2005.
17. (a) Boultif, A.; Louer, D. J. Appl. Crystallogr. 1991, 24, 987; (b) Boultif, A.; Louer, D.
J. Appl. Crystallogr. 2004, 37, 724.
18. David, W. I. F.; Shankland, K.; van de Streek, J.; Pidcock, E.; Motherwell, W. D. S.;
Cole, J. C. J. Appl. Crystallogr. 2006, 39, 910.
4.5. Powder X-ray diffraction
The synchrotron X-ray powder diffraction data for the poly-
crystalline sample of the desolvated 6 were recorded at ambient
19. Larson, A. C.; Von Dreele, R. B. GSAS, Los Alamos Laboratory Report No. LA-UR-
86-748, 1987, p 19.