Fluoride-induced chemiluminescent decomposition of dioxetanes bearing a siloxyaryl moiety to produce an alkyl aryl ketone as an emitter

Article abstract of DOI:10.1016/S0040-4020(03)00727-0

Tetrabutylammonium fluoride induces the decomposition of 1-tert-butyl-4,4-dimethyl-5-(3-siloxyphenyl)-2,6,7-trioxabicyclo[3.2.0] heptane (4a) in DMSO to form an oxyanion of aromatic ketone (14a) as an emitter with high singlet-chemiexcitation yield comparable with that for a chemically initiated electron exchange luminescence (CIEEL) active dioxetane producing an oxyanion of aromatic ester as an emitter. A 7-siloxynaphthalen-2-yl analog (4b) was found on similar treatment to emit light with the maximum wavelength the longest among CIEEL-active dioxetanes hitherto known.

Full text of DOI:10.1016/S0040-4020(03)00727-0

Tetrahedron 59 (2003) 4811–4819
Fluoride-induced chemiluminescent decomposition of
dioxetanes bearing a siloxyaryl moiety to produce an alkyl aryl
ketone as an emitter
*
Nobuko Watanabe, Yasuhiro Nagashima, Takahiro Yamazaki and Masakatsu Matsumoto
Department of Chemistry, Kanagawa University, Tsuchiya, Hiratsuka, Kanagawa 259-1293, Japan
Received 3 April 2003; accepted 28 April 2003
Abstract—Tetrabutylammonium fluoride induces the decomposition of 1-tert-butyl-4,4-dimethyl-5-(3-siloxyphenyl)-2,6,7-trioxabicy-
clo[3.2.0]heptane (4a) in DMSO to form an oxyanion of aromatic ketone (14a) as an emitter with high singlet-chemiexcitation yield
comparable with that for a chemically initiated electron exchange luminescence (CIEEL) active dioxetane producing an oxyanion of
aromatic ester as an emitter. A 7-siloxynaphthalen-2-yl analog (4b) was found on similar treatment to emit light with the maximum
wavelength the longest among CIEEL-active dioxetanes hitherto known. q 2003 Elsevier Science Ltd. All rights reserved.
Since the discovery of 1,2-dioxetanes their chemistry has
been extensively studied. These high-energy molecules
have been established to generate mainly triplet-excited
carbonyl fragments on thermal decomposition.1 In contrast,
dioxetanes substituted with an aromatic electron donor
display intramolecular chemically initiated electron
exchange luminescence (CIEEL),2–4 in which a charge
transfer from an aromatic electron donor to the dioxetane
ring occurs to induce its decomposition with light emission.
A representative of such CIEEL-active dioxetane is a
thermally stable 3-methoxy-3-(3-siloxyphenyl)-1,2-
dioxetane (1). A siloxyphenyl of 1 is deprotected with
fluoride to produce an unstable dioxetane (2) bearing a
m-oxyphenyl anion, CIEEL-decay of which affords a
singlet-excited aromatic ester (3).4,5 After the reports on
dioxetane (1) and related peroxides, a variety of 3-alkoxy-
4,4-dialkyl-3-aryl-1,2-dioxetanes have been synthesized
and examined from the viewpoints of understanding the
chemiluminescent and bioluminescent mechanisms and of
application to biological analysis.6,7
adamantylidene part in dioxetane (1) has been regarded
chiefly as a stabilizer to improve thermal persistency of the
dioxetane ring. On the other hand, there has been little
known of the CIEEL-active dioxetanes producing an
oxyphenyl ketone as an emitter8,9 though the base-induced
chemiluminescent decomposition of benzofuran-
dioxetanes10 and indole-dioxetanes11 as rather special
examples and spirodioxetanes producing an excited
acridone12 or an excited xanthone13 have been known.
These facts prompted us to synthesize 3-alkoxy-4-(siloxy-
aryl)-1,2-dioxetanes, which would give a rather simple
aromatic ketone fragment, and to examine whether their
fluoride-induced decomposition occurs to afford effectively
an excited anion of the oxyaryl ketone as an emitter. The
realized dioxetanes were 1-tert-butyl-4,4-dimethyl-5-
(siloxyaryl)-2,6,7-trioxabicyclo[3.2.0]heptanes (4a–4c)
which were then examined (Scheme 1).
An isomeric bicyclic dioxetane of 4a, namely, 5-tert-butyl-
4,4-dimethyl-1-(3-siloxyphenyl)-2,6,7-trioxabicyclo[3.2.0]-
heptane (5), possesses marked thermal stability, which is
likely attributed to the steric repulsion between a
4-methyl(s) and a 5-substituent (tert-butyl) as well as to
the inhibition of twisting of a dioxetane ring by a fused five-
membered ring. The dioxetane (5) is, furthermore, an
effective precursor to form at will a CIEEL-active dioxetane
bearing an oxyanion of the phenolic moiety on treatment
with tetrabutylammonium fluoride (TBAF) in an aprotic
solvent such as DMSO and acetonitrile.14 Hence, we
planned to synthesize 4,4-dimethyl-2,6,7-trioxabicyclo-
[3.2.0]heptanes (4) in which both tert-butyl and siloxy-
substituted aryl groups exist as in the case of 5 except the
positions of these two substituents are exchanged. We chose
One structural characteristic of the hitherto-known CIEEL-
active dioxetanes is that they consist of an alkoxy and an
aromatic electron donor at the geminal position so that they
afford, after the above deprotection, an aromatic ester as an
emitter. For example, 1 produces an excited aromatic ester
(3) while a dialkyl ketone fragment, namely, adamantanone
formed concomitantly, gives little light so that the
Keywords: dioxetane; CIEEL; chemiluminescence; aromatic ketone; red
light.
*
Corresponding author. Fax: þ81-463-58-9684;
e-mail: matsumo@chem.kanagawa-u.ac.jp
0040–4020/03/$ - see front matter q 2003 Elsevier Science Ltd. All rights reserved.
doi:10.1016/S0040-4020(03)00727-0

4812
N. Watanabe et al. / Tetrahedron 59 (2003) 4811–4819
Scheme 1.
3-siloxyphenyl (4a), 7-siloxynaphthalen-2-yl (4b), and
4-siloxyphenyl (4c) as representatives for a siloxy-sub-
stituted aryl group for 4, since the behavior of these
dioxetanes can presumably be easily compared with those of
the known CIEEL-active dioxetanes (1), (5), (6a)15 (6b)16
and (6c)17 bearing the corresponding aromatic electron
donor for CIEEL in the TBAF/DMSO system.
LiAlH4 to a propanediol (9). The primary OH group of a
diol (9) was selectively esterified with pivaloyl chloride to
yield a monoester (10) of 9, which was successively
oxidized into the desired ketoester (11).
When a solution of dihydrofuran (7a) (100 mg) and a
catalytic amount of tetraphenylporphin (TPP) in dichloro-
methane (10 mL) was irradiated externally with 940 W
Na-lamp under an oxygen atmosphere at 2788C for 1 h, 7a
was transformed exclusively to a dioxetane (4a), which was
isolated as colorless granules in 83.0% yield after
chromatographic purification. The structure of 4a was
characterized by 1H NMR, 13C NMR, IR, Mass, and
HRMS spectral analysis. The other dihydrofurans (7b and
7c) were similarly oxygenated to give the corresponding
1,2-dioxetanes (4b and 4c) in high yields. These dioxetanes
(4a–4c) were sufficiently thermally stable to permit
handling at room temperature.
1. Results and discussion
1.1. Synthesis of 1-tert-butyl-4,4-dimethyl-5-(siloxyaryl)-
2,6,7-trioxabicyclo[3.2.0]heptanes
The sensitized photooxygenation would be an effective tool
to prepare the desired dioxetanes (4a–4c) from the
corresponding
4-aryl-5-tert-butyl-3,3-dimethyl-2,3-
dihydrofurans (7a–7c) similarly to the case of a dioxetane
(5). Thus, the dihydrofurans (7a–7c) were synthesized from
their methoxyaryl-analogs (12) by means of their demethyl-
ation yielding hydroxyaryl-analogs (13) with EtSNa/
dimethylformamide (DMF) and successive silylation with
tert-butyldimethylsilyl chloride. Methoxyaryl-substituted
dihydrofurans (12) as a key intermediate were synthesized
by the McMurry reductive coupling18 of the corresponding
2,2-dimethylpropanoic acid (pivalic acid) esters of a
3-(methoxyaryl)-2,2-dimethyl-3-oxo-1-propanol (11),
which were synthesized in several steps starting from
ethyl 2-methylpropanoate and aromatic aldehydes as
illustrated in Scheme 2. The first step was the coupling of
a lithium enolate of ethyl 2-methylpropanoate with an
aromatic aldehyde to afford a 3-aryl-3-hydroxy-2,2-
dimethylpropanoate (8), which was reduced, in turn, with
1.2. TBAF-induced CIEEL-decay of 1-tert-butyl-4,4-
dimethyl-5-(siloxyaryl)-2,6,7-trioxabicyclo
[3.2.0]heptanes
A siloxyphenyl-substituted dioxetane (1) is triggered with
TBAF in an aprotic solvent such as DMSO and acetonitrile;
its desilylation with fluoride affords an unstable phenolate-
substituted dioxetane, which decomposes rapidly by the
CIEEL process. It has been reported very recently for the
fluoride-triggered CIEEL process of a siloxyphenyl-
substituted dioxetane that the CIEEL-decay rate of
dioxetane follows pseudo-first-order kinetics independent
of the TBAF concentration when an excess of fluoride
concentration is used.5 Therefore, we used a large excess of

N. Watanabe et al. / Tetrahedron 59 (2003) 4811–4819
4813
Scheme 2.
Table 1. F2-Induced chemiluminescence of 5-aryl-1-tert-butyl-4,4-
dimethyl-2,6,7-trioxabicyclo[3.2.0]heptanes (4) and their related
dioxetanes in DMSO
dioxetanes 5 and 6a, in which an aromatic electron donor
is a 3-oxyphenyl anion equally to the case of 4a, one realizes
that (a) fluoride-induced CIEEL-decay for 4a occurs far
CIEEL
max
a
k (s21
)
t1/2 (s)
more slowly than for 5 and 6a, (b) emission from 4a is
yellow light, while that from 5 and 6a is blue (l
Dioxetane
l
(nm)
FCIEEL
FS
CIEEL
max
¼463–
1.5£1022
0.20
0.24
0.21
0.63
0.48
0.31
2.8£1024
0.15
0.11
2500
4.6
6.3
466 nm), and (c) chemiluminenscent efficiency F CIEEL is
considerably lower for 4a than for 5 and 6a.
4a
549
466
463
642
5b
6ac
4b
6bd
4c
5.6£1023
1.3£1024
5500
250
6.3£1022
–
2.8£1023
The ease of intramolecular CIEEL-decay depends on the
ease of electron transfer from an aromatic electron donor to
O–O of the dioxetane ring. Therefore, a dioxetane bearing
an aryl moiety, which is oxidized the more easily, would
undergo the CIEEL-decay the more rapidly.19 However,
both dioxetanes (4a) and (5) bear a 3-oxyphenyl moiety, so
that the ease of electron transfer for 4a might be little
different in an electronic factor from that for 5. On the other
hand, it has been suggested very recently for a CIEEL-active
dioxetane bearing a phenolic moiety that an intramolecular
electron transfer occurs preferentially from the phenolic
electron donor to O–O of the dioxetane, when the phenolic
ring lies in a certain conformation(s).20 According to the
suggestion, the electron transfer should become difficult to
occur when the aromatic ring is prevented from rotating
freely by the proximal substituent(s) on the dioxetane ring.
Such steric interaction of the aromatic ring with the
neighboring entities would be larger for 4a than for 5: the
neighboring entities are the 1-tert-butyl and the methyl(s) at
the 4-position for 4a, while the 5-tert-butyl and oxygen of
the tetrahydrofuran ring for 5. This is likely the reason why
4a undergoes the CIEEL-decay far more slowly than 5.
558
e
e
e
e
e
6cf
463
5.8£1024
–
.0.7
,1
A solution of a dioxetane in DMSO (1.0£1025 M, 1 mL) was added to a
solution of TBAF in DMSO (1.0£1022 M, 2 mL) at 258C.
a
Relative chemiluminescent efficiency based on the value for 1 (Ref. 5):
lmax¼466 nm, F CIEEL¼0.29, t1/2¼5 s.
b
Ref 14.
Ref 15.
c
d
Ref 16.
No chemiluminescence could be detected.
Ref. 17.
e
f
TBAF to examine the fluoride-induced decomposition of
dioxetanes (4) for simplifying the system.
When a solution of 4a in DMSO (1.0£1025 mol dm23
,
1 mL) was added to a TBAF solution in DMSO
(1.0£1022 mol dm23, 2 mL) at 258C, 4a underwent
CIEEL
CIEEL-decay to emit light with maximum wavelength
l
¼549 nm,
chemiluminescent
efficiency
max
F CIEEL¼1.5£1022, CIEEL-decay rate k¼2.8£1024 s21
,
and half-life t1/2(¼loge 2/k)¼2500 s. These chemilumines-
cent properties are shown together with those for a
naphthyl-analog (4b), 4-siloxyphenyl-analog (4c), and
related dioxetanes (5, and 6a–6c) in Table 1. Comparing
the chemiluminescent properties of 4a with those for
CIEEL
max
The maximum wavelength of CIEEL emission (l
) of
4a coincided with fluorescence maximum (lflmax) of the
corresponding spent reaction mixture, from which a

4814
N. Watanabe et al. / Tetrahedron 59 (2003) 4811–4819
3-hydroxyphenyl ketone (14a) was isolated in high yield.
The fluorescence maximum (lflmax) of an oxyanion produced
from 14a by treatment with TBAF in DMSO coincided also
longest among CIEEL-active dioxetanes hitherto known.
On the other hand, a 4-siloxyphenyl-analog (4c) gave no
detectable light emission in the TBAF/DMSO system.
CIEEL
with l
undoubtedly an emitter for the CIEEL of 4a, of which
of 4a. Hence, an oxyanion of 14a is
max
fluorescence efficiency F fl was estimated to be 7.2£1022
.
3. Experimental
3.1. General
Since the chemiluminenscent yield (F CIEEL) is equal to the
product of FS£F fl, FS was estimated to be 0.21 for 4a. The
results reveal that a CIEEL-active dioxetane, such as 4a,
producing an aromatic ketone as the emitter causes singlet-
chemiexcitation in high yield which bears comparison with
that for dioxetanes (1, 5, and 6a) giving an aromatic ester as
the emitter (Table 1).
Melting points were measured with a Yanako MP-S3
melting point apparatus and are uncorrected. IR spectra
were taken on a JASCO FT/IR-300 infrared spectrometer.
1H and 13C NMR spectra were recorded on JEOL EX-400
and JEOL EPC-500 spectrometer. Mass spectra were
obtained by using JEOL JMS-AX-505H, JEOL JMS-T-
100LC (AccuTOF), and/or Hitachi M80B mass spec-
trometers. Chemiluminescences were measured by Hitachi
F-4010 spectrometer, JASCO FP-750 spectrometer, and/or
Hamamatsu Photonics PMA-11 multi-channel detector.
Reagents were purchased from Aldrich, Tokyo Chemical
Industries, Wako Pure Chemical Industries and/or Kanto
Chemical Industries. Column chromatography was carried
out with silica gel, unless otherwise stated.
CIEEL
max
The result that a dioxetane (4a) affords light with l
considerably longer than that for 1, 5, and 6a, and the
reported result that 6b, which produces an excited oxyanion
of a 7-hydroxynaphthalene-2-carboxylate emitting yellow
CIEEL
light (l
2-yl analog (4b) should become a new chemiluminescent
substrate emitting red light. Treatment of 4b with TBAF
¼558 nm), suggest that a 7-siloxynaphthalen-
max
CIEEL
max
similarly to the case of 4a afforded light with l
¼642
nm, F CIEEL¼5.6£1023, k¼1.3£1024 s21, and t1/2¼5500 s.
CIEEL
The result was gratifying beyond expectation: (a) 4b emits
red light with the longest l
dioxetanes hitherto known, such as 6b and its phosphate-
among the CIEEL-active
3.1.1. Ethyl 3-hydroxy-3-(3-methoxyphenyl)-2,2-
dimethylpropanoate (8a). Ethyl 2-methylpropanoate
(13.7 mL, 0.102 mol) was added to a solution of lithium
diisopropylamide (0.104 mol) in THF (100 mL) at 2788C
and stirred for 30 min under nitrogen atmosphere. To the
solution, 3-methoxybenzaldehyde (10.0 mL, 0.082 mol)
was added and stirred for 1.5 h. The reaction mixture was
poured into NH4Cl aq. solution and extracted with ethyl
acetate (AcOEt). The organic layer was dried over MgSO4
and concentrated. The residue was chromatographed on
silica gel and eluted with hexane–AcOEt (5:1–2:1) to give
8a as a colorless oil in quantitative yield (20.9 g). 1H NMR
(400 MHz, CDCl3): dH 1.12 (s, 3H), 1.15 (s, 3H), 1.28 (t,
J¼7.1 Hz, 3H), 3.15 (d with fine coupling, J¼4.3 Hz, 1H),
3.80 (s, 3H), 4.19 (q, J¼7.1 Hz, 2H), 6.82 (ddd, J¼8.1, 2.6,
0.9 Hz, 1H), 6.86–6.90 (m, 2H), 7.23 (t, J¼8.1 Hz, 1H). IR
(liquid film): 3494, 2980, 1717, 1602, 1259 cm21. Mass (EI)
(m/z, %): 252 (Mþ, 9), 137 (28), 116 (100), 109 (40), 88
(48). HRMS (ESI): 275.1282, calcd for C14H20O4Na
(MþNaþ) 275.1259.
max
¼550–560 nm),21 a benzofuran-substituted
CIEEL
max
analog (l
dioxetane (16) (l
CIEEL
max
¼615–620 nm, F CIEEL¼1.6£1024
–
and a benzothiophene-substituted dioxetane
2.1£1024 22
)
(l
F CIEEL¼1.4£1024
–
CIEEL
max
(17)
¼615–628 nm,
2.1£1024),22 and (b) chemiluminescent efficiency is rather
CIEEL
better than that for 16 and 17 (Table 1). The maximum
wavelength of CIEEL emission (l
) of 4b coincided not
max
only with fluorescence maximum (lflmax) of the correspond-
ing spent mixture but also with lflmax of an oxyanion of
7-hydroxynaphthalen-2-yl ketone (14b) in the TBAF–
DMSO system. Thus, F fl and Fs for 4b were estimated to
be 0.018 and 0.31, respectively.
A 4-oxyphenyl-substituted dioxetane such as 6c has been
known also to emit light though far less effectively than its
3-oxyphenyl-analog such as 1, 5, and 6a on CIEEL-
decay.17,23 From the analogy of the results for 4a and 4b,
it is inferred a dioxetane bearing a 4-siloxyphenyl moiety
(4c) was expected also to emit light though weak. However,
no light emission was observed for 4c on treatment with
TBAF in DMSO, though the expected decomposition of 4c
proceeded to give the corresponding ketoester (14c), an
oxyanion of which showed little fluorescence in TBAF/
DMSO.
3.1.2. Ethyl 3-hydroxy-3-(7-methoxynaphthalen-2-yl)-
2,2-dimethylpropanoate (8b). Similarly to the preparation
of 8a from 3-methoxybenzaldehyde, the coupling reaction
of an enolate of ethyl 2-methylpropanoate with 7-methoxy-
naphthalene-2-carbaldehyde was carried out to give 8b as a
1
colorless oil in 86.9% isolated yield. H NMR (400 MHz,
CDCl3): dH 1.16 (s, 3H), 1.19 (s, 3H), 1.28 (t, J¼7.1 Hz,
3H), 3.26 (d, J¼4.4 Hz, 1H), 3.92 (s, 3H), 4.21 (q,
J¼7.1 Hz, 2H), 5.04 (d, J¼4.4 Hz, 1H), 7.11–7.15 (m,
2H), 7.30 (dd, J¼8.3, 1.5 Hz, 1H), 7.68 (broad s, 1H), 7.69–
7.74 (m, 2H). IR (liquid film): 3500, 2979, 2938, 1717,
1607, 1514, 1216 cm21. Mass (EI) (m/z, %): 302 (Mþ, 22),
187 (91), 186 (48), 159 (47), 144 (27), 116 (100). HRMS
(EI): 302.1510, calcd for C18H22O4 302.1518.
2. Conclusion
Treatment of 1-tert-butyl-4,4-dimethyl-5-(3-siloxyphenyl)-
2,6,7-trioxabicyclo[3.2.0]heptane (4a) with TBAF in
DMSO generates a CIEEL-active dioxetane, which decom-
poses smoothly to form an oxyanion of aromatic ketone
(14a) as an emitter with high singlet-chemiexcitation yield
comparable with that for a CIEEL-active dioxetane
producing an oxyanion of aromatic ester as an emitter. A
7-siloxynaphthalen-2-yl analog (4b) was found on treatment
with TBAF to emit light with the maximum wavelength the
3.1.3. Ethyl 3-hydroxy-3-(4-methoxyphenyl)-2,2-
dimethylpropanoate (8c). Similarly to the preparation of
8a from 3-methoxybenzaldehyde, the coupling reaction of

N. Watanabe et al. / Tetrahedron 59 (2003) 4811–4819
4815
an enolate of ethyl 2-methylpropanoate with 4-methoxy-
benzaldehyde was carried out to give 8c as colorless
granules, melted at 72.0–72.58C (from hexane–AcOEt), in
87.3% isolated yield. 1H NMR (400 MHz, CDCl3): dH 1.09
(s, 3H), 1.13 (s, 3H), 1.28 (t, J¼7.1 Hz, 3H), 3.10 (d,
J¼4.2 Hz, 1H), 3.81 (s, 3H), 4.18 (q, J¼7.1 Hz, 2H), 4.85
(d, J¼4.2 Hz, 1H), 6.86 (d with fine coupling, J¼8.5 Hz,
2H), 7.23 (t, d with fine coupling, J¼8.5 Hz, 2H). IR (KBr):
3455, 2975, 1704, 1514, 1244, 1026 cm21. Mass (EI) (m/z,
%): 252 (Mþ, 2), 207 (2), 137 (100), 116 (20). HRMS (EI):
252.1349, calcd for C14H20O4 252.1362.
methoxyphenyl)-2,2-dimethyl-1,3-propanediol (9a) (3.17 g,
15.1 mmol) and pyridine (3.5 mL, 43.3 mmol) in 1,2-
dichloroethane (25 mL) under nitrogen atmosphere at
room temperature and then heated at refluxing temperature
for 45 min. The reaction mixture was poured into NaCl aq.
solution and extracted with AcOEt. The organic layer was
washed with NaCl aq. solution, dried over MgSO4, and
concentrated in vacuo. The residue was chromatographed
on silica gel with hexane–AcOEt (4:1) to afford 10a as a
1
colorless oil in 74.9% yield (3.32 g). H NMR (400 MHz,
CDCl3): dH 0.88 (s, 3H), 0.97 (s, 3H), 1.25 (s, 9H), 3.74 (d,
J¼11.0 Hz, 1H), 3.81 (s, 3H), 4.18 (d, J¼11.0 Hz, 1H), 4.55
(s, 1H), 7.30 (ddd, J¼8.2, 2.5, 0.9 Hz, 1H), 6.86–6.89 (m,
2H), 7.23 (t, J¼8.2 Hz, 1H). IR (liquid film): 3488, 2973,
2873, 1705, 1608, 1583 cm21. Mass (EI) (m/z, %): 294
(Mþ, 3), 174 (11), 136 (100), 109 (12). HRMS (ESI):
317.1763, calcd for C17H26O4Na (MþNaþ) 317.1729.
3.1.4. 1-(3-Methoxyphenyl)-2,2-dimethyl-1,3-propane-
diol (9a). A solution of ethyl 3-hydroxy-3-(3-methoxy-
phenyl)-2,2-dimethylpropanoate (8a) (6.11 g, 24.2 mmol)
in THF (20 mL) was added drop by drop to a suspension of
lithium aluminum hydride (LAH) (902 mg, 23.8 mmol) in
THF (40 mL) under nitrogen atmosphere at 08C and stirred
for 1 h. After the usual work-up, the crude product was
purified by column chromatography on silica gel with
hexane–AcOEt (5:1–1:1) to give 9a as a colorless oil in
67.8% yield (3.45 g). 1H NMR (400 MHz, CDCl3): dH 0.87
(s, 3H), 0.89 (s, 3H), 2.70 (dd, J¼5.6, 4.9 Hz, 1H), 2.95 (d,
J¼2.9 Hz, 1H), 3.52 (dd, J¼10.7, 4.9 Hz, 1H), 3.60 (dd,
J¼10.7, 5.6 Hz, 1H),3.82 (s, 3H), 4.64 (d, J¼2.9 Hz, 1H),
6.83 (ddd, J¼8.2, 2.4, 1.1 Hz, 1H), 6.89–6.93 (m, 2H), 7.25
(t, J¼8.2 Hz, 1H). IR (liquid film): 3367, 2959, 2873, 1602,
1585, 1258 cm21. Mass (EI) (m/z, %): 210 (Mþ, 3), 192
(14), 136 (100), 109 (23). HRMS (ESI): 233.1165, calcd for
C12H18O3Na (MþNaþ) 233.1154.
3.1.8. 3-Hydroxy-3-(7-methoxynaphthalen-2-yl)-2,2-
dimethyl-1-propyl 2,2-dimethylpropanoate (10b). Simi-
larly to the preparation of 10a from 9a, the esterification of
1-(7-methoxynaphthalen-2-yl)-2,2-dimethyl-1,3-propanediol
(9b) with pivaloyl chloride was carried out to give 10b as
colorless granules, melted at 133.0–134.08C (from hexane–
AcOEt), in72.4%isolatedyield.1HNMR(400 MHz,CDCl3):
dH 0.92 (s, 3H), 1.01 (s, 3H), 1.27 (s, 9H), 2.45 (broad s, 1H),
3.79 (d, J¼10.7 Hz, 1H), 3.92 (s, 3H), 4.25 (d, J¼10.7 Hz,
1H), 4.72 (s, 1H), 7.11–7.15 (m, 2H), 7.30 (d with fine
coupling, J¼8.3 Hz, 1H), 7.66 (s, 1H), 7.70–7.74 (m, 2H). IR
(KBr): 3496, 3056, 2972, 2937, 2872, 1701, 1607, 1514,
1217 cm21. Mass (EI) (m/z, %): 344 (Mþ, 2), 186 (100), 159
(15). HRMS (ESI): 344.1991, calcd for C21H28O4 344.1998.
3.1.5. 1-(7-Methoxynaphthalen-2-yl)-2,2-dimethyl-1,3-
propanediol (9b). Similarly to the preparation of 9a from
8a, the reduction of ethyl 3-hydroxy-3-(7-methoxynaphtha-
len-2-yl)-2,2-dimethylpropanoate (8b) with LAH was
carried out to give 9b as colorless needles, melted at
122.0–123.08C (from dichloromethane), in 55.4% isolated
yield. 1H NMR (400 MHz, CDCl3): dH 0.91 (s, 3H), 0.95 (s,
3H), 3.56 (d, J¼10.7 Hz, 1H), 3.66 (d, J¼10.7 Hz, 1H), 3.93
(s, 3H), 4.82 (s, 1H), 7.12–7.16 (m, 2H), 7.33 (dd, J¼8.3,
1.7 Hz, 1H), 7.69–7.75 (m, 3H). IR (KBr): 3368, 2965,
2871, 1605, 1514, 1215, 1174 cm21. Mass (EI) (m/z, %):
260 (Mþ, 5), 186 (100), 159 (21), 144 (15). HRMS (EI):
260.1406, calcd for C16H20O3 260.1412.
3.1.9. 3-Hydroxy-3-(4-methoxyphenyl)-2,2-dimethyl-1-
propyl 2,2-dimethylpropanoate (10c). Similarly to the
preparation of 10a from 9a, the esterification of 1-(4-
methoxyphenyl)-2,2-dimethyl-1,3-propanediol (9c) with
pivaloyl chloride was carried out to give 10c as colorless
granules, melted at 78.0–79.08C (from hexane), in 68.5%
isolated yield. 1H NMR (400 MHz, CDCl3): dH 0.85 (s, 3H),
0.95 (s, 3H), 1.25 (s, 9H), 2.28 (d, J¼2.9 Hz, 1H), 3.73 (d,
J¼10.7 Hz, 1H), 3.81 (s, 3H), 4.16 (d, J¼10.7 Hz, 1H), 4.53
(d, J¼2.9 Hz, 1H), 6.86 (d with fine coupling, J¼8.8 Hz,
2H), 6.86 (d with fine coupling, J¼8.8 Hz, 2H). IR (KBr):
3484, 2967, 1702, 1512, 1253, 1193 cm21. Mass (EI) (m/z,
%): 294 (Mþ, trace), 136 (100), 135 (39). HRMS (EI):
294.1837, calcd for C17H26O4 294.1831.
3.1.6. 1-(4-Methoxyphenyl)-2,2-dimethyl-1,3-propane-
diol (9c). Similarly to the preparation of 9a from 8a, the
reduction of ethyl 3-hydroxy-3-(4-methoxyphenyl)-2,2-
dimethylpropanoate (8c) with LAH was carried out to
give 9c as colorless granules, melted at 78.0–79.08C (from
hexane), in 63.5% isolated yield. 1H NMR (400 MHz,
CDCl3): dH 0.85 (s, 3H), 0.87 (s, 3H), 2.70 (dd, J¼5.9,
5.4 Hz, 1H), 2.75 (d, J¼2.7 Hz, 1H), 3.52 (dd, J¼10.7,
5.9 Hz, 1H), 3.82 (s, 3H), 4.63 (d, J¼2.7 Hz, 1H), 6.88 (d
with fine coupling, J¼8.8 Hz, 2H), 7.26 (d with fine
coupling, J¼8.8 Hz, 2H). IR (KBr): 3351, 3234, 2967,
1612, 1518, 125, 1035 cm21. Mass (EI) (m/z, %): 210 (Mþ,
trace), 192 (4), 137 (100), 109 (17). HRMS (EI): 210.1269,
calcd for C12H18O3 210.1256.
3.1.10. 3-(3-Methoxyphenyl)-2,2-dimethyl-3-oxopropan-
1-yl 2,2-dimethylpropanoate (11a). 3-Hydroxy-3-(3-meth-
oxyphenyl)-2,2-dimethyl-1-propyl 2,2-dimethylpropanoate
(10a) (2.98 g, 10.1 mmol) was stirred together with MnO2
(20.5 g) in benzene (30 mL) at refluxing temperature for
30 min. The reaction mixture was filtered through celite to
remove the inorganic oxide and the benzene solution was
concentrated in vacuo. The residue was chromatographed
on silica gel with hexane–AcOEt (4:1) to give 11a as a
1
colorless oil in 70.0% yield (2.07 g). H NMR (400 MHz,
CDCl3): dH 1.14 (s, 9H), 1.37 (s, 6H), 3.83 (s, 3H), 4.25 (s,
2H), 7.01 (ddd, J¼8.2, 2.6, 0.9 Hz, 1H), 7.12 (dd, J¼2.6,
1.6 Hz, 1H), 7.20 (ddd, J¼7.6, 1.6, 0.9 Hz, 1H), 7.31 (dd,
J¼8.2, 7.6 Hz, 1H). IR (liquid film): 2973, 1731, 1683,
1582 cm21. Mass (EI) (m/z, %): 292 (Mþ, 4), 236 (33), 135
3.1.7. 3-Hydroxy-3-(3-methoxyphenyl)-2,2-dimethyl-1-
propyl 2,2-dimethylpropanoate (10a). Pivaloyl chloride
(2.1 mL, 17.1 mmol) was added to a solution of 1-(3-

4816
N. Watanabe et al. / Tetrahedron 59 (2003) 4811–4819
(100), 107 (9). HRMS (ESI): 315.1609, calcd for
C17H24O4Na (MþNaþ) 315.1572.
preparation of 12a from 11a, the McMurry coupling of 3-
(7-methoxynaphthalen-2-yl)-2,2-dimethyl-3-oxopropan-1-
yl 2,2-dimethylpropanoate (11b) was carried out to give 12b
as colorless crystals melted at 103.0–105.08C (from
hexane–AcOEt), in 66.3% yield. 1H NMR (400 MHz,
CDCl3): dH 0.97 (s, 9H), 1.05 (s, 6H), 2.93 (s, 3H), 4.02 (s,
2H), 7.09–7.14 (m, 3H), 7.47 (broad s, 1H), 7.68 (d,
J¼8.3 Hz, 1H), 7.72 (d, J¼9.8 Hz, 1H). IR (KBr): 3051,
2958, 2930, 2864, 1604, 1509, 1215 cm21. Mass (EI) (m/z,
%): 310 (Mþ, 59), 295 (100), 239 (30). HRMS (EI):
310.1926, calcd for C21H26O2 310.1933.
3.1.11. 3-(7-Methoxynaphthalen-2-yl)-2,2-dimethyl-3-
oxopropan-1-yl 2,2-dimethylpropanoate (11b). Similarly
to the preparation of 11a from 10a, the oxidation of 3-
hydroxy-3-(7-methoxynaphthalen-2-yl)-2,2-dimethyl-1-pro-
pyl 2,2-dimethylpropanoate (10b) with MnO2 was carried out
to give 11b as a colorless oil in 83.8% isolated yield. 1H NMR
(400 MHz, CDCl3): dH 1.14 (s, 9H), 1.45 (s, 6H), 3.94 (s, 3H),
4.33 (s, 2H), 7.17 (d, J¼2.4 Hz, 1H), 7.23 (dd, J¼8.8, 2.4 Hz,
1H), 7.57 (dd, J¼8.3, 2.0 Hz, 1H), 7.75 (d, J¼8.8 Hz, 1H),
7.78 (d, J¼8.3 Hz, 1H), 8.04 (broad s, 1H). IR (liquid film):
2973, 2936, 2872, 1604, 1509, 1460, 1218 cm21. Mass (EI)
(m/z, %): 342 (Mþ, 10), 286 (17), 185 (100), 157 (18). HRMS
(EI): 342.1818, calcd for C21H26O4 342.1831.
3.1.15. 5-tert-Butyl-4-(4-methoxyphenyl)-3,3-dimethyl-
2,3-dihydrofuran (12c). Similarly to the preparation of
12a from 11a, the McMurry coupling of 3-(4-methoxy-
phenyl)-2,2-dimethyl-3-oxopropan-1-yl
2,2-dimethyl-
propanoate (11c) was carried out to give 12c as colorless
crystals melted at 49.0–50.08C (from hexane–AcOEt), in
79.0% yield. 1H NMR (400 MHz, CDCl3): dH 0.95 (s, 9H),
0.99 (s, 6H), 3.81 (s, 3H), 3.96 (s, 2H), 6.82 (d with fine
coupling, J¼8.8 Hz, 2H), 7.01 (d with fine coupling,
J¼8.8 Hz, 2H). IR (KBr): 2959, 2870, 1607, 1508, 1243,
1114 cm21. Mass (EI) (m/z, %): 260 (Mþ, 58), 245 (100),
189 (31). HRMS (EI): 260.1773, calcd for C17H24O2
260.1776.
3.1.12. 3-(4-Methoxyphenyl)-2,2-dimethyl-3-oxopropan-
1-yl 2,2-dimethylpropanoate (11c). Similarly to the
preparation of 11a from 10a, the oxidation of 3-hydroxy-
3-(4-methoxyphenyl)-2,2-dimethyl-1-propyl 2,2-dimethyl-
propanoate (10c) with MnO2 was carried out to give 11c as a
1
colorless oil in 83.8% isolated yield. H NMR (400 MHz,
CDCl3): dH 1.12 (s, 9H), 1.40 (s, 6H), 3.85 (s, 3H), 4.29 (s,
2H), 6.90 (d with fine coupling, J¼9.3 Hz, 2H), 7.78 (d with
fine coupling, J¼9.3 Hz, 2H). IR (liquid film): 2972, 1730,
1603, 1258, 1035 cm21. Mass (EI) (m/z, %): 236 [Mþ256
(Me2CvCH2), trace], 135 (100). CIMS MHþ: 293. HRMS
(EI): 236.1039, calcd for C13H16O4 236.1049.
3.1.16. 5-tert-Butyl-4-(3-hydroxyphenyl)-3,3-dimethyl-
5-tert-Butyl-4-(3-methoxy-
2,3-dihydrofuran
(13a).
phenyl)-3,3-dimethyl-2,3-dihydrofuran (12a) (361 mg,
1.39 mmol) was stirred together with sodium ethanethiolate
(4.6 mmol, prepared from ethanethiol and NaH) in DMF
(4 mL) under nitrogen atmosphere at refluxing temperature
for 2 h. The reaction mixture was poured into NaCl aq.
solution and extracted with AcOEt. The organic layer was
washed with water, dried over MgSO4, and concentrated in
vacuo. The residue was chromatographed on silica gel and
eluted with AcOEt–hexane (1:5) to give 13a as colorless
crystals melted at 130.5–132.08C (from hexane–AcOEt), in
80.2% yield. 1H NMR (400 MHz, CDCl3): dH 0.97 (s, 9H),
1.01 (s, 6H), 3.96 (s, 2H), 4.67 (s, 1H), 6.60 (s with fine
coupling, 1H), 6.69 (d, J¼7.3 Hz, 1H), 6.73 (dd, J¼8.3,
2.7 Hz, 1H), 7.14 (dd, J¼8.3, 7.3 Hz, 1H). IR (KBr): 3406,
2962, 1671, 1611, 1577 cm21. Mass (EI) (m/z, %): 246
(Mþ, 47), 231 (100), 175 (24). HRMS (EI): 246.1618, calcd
for C16H22O2 246.1620.
3.1.13. 5-tert-Butyl-4-(3-methoxyphenyl)-3,3-dimethyl-
2,3-dihydrofuran (12a). Titanium (III) chloride (80%,
6.12 g, 31.8 mmol) was stirred in dry THF (100 mL) at ice-
cooled temperature for 30 min. To the solution, LAH
(630 mg, 16.6 mmol) was added and stirred for 30 min, and
successively triethylamine (3.0 mL, 21.6 mmol) was added
and stirred at refluxing temperature for 30 min. To this
solution of low-valent titanium, a solution of 3-(3-
methoxyphenyl)-2,2-dimethyl-3-oxopropan-1-yl
2,2-
dimethylpropanoate (11a) (1.01 g, 3.45 mmol) in THF
(20 mL) was added dropwise for 1 h and the mixture was
refluxed for 1 h. After cooling, the reaction mixture was
poured carefully into NaCl aq. solution and extracted with
AcOEt. The organic layer was washed with NaHCO3 aq.
solution, dried over MgSO4, and concentrated in vacuo. The
crude mixture of 6-hydroxy-4-(3-methoxyphenyl)-2,2,5,5-
tetramethyl-3-hexanone was dissolved in dichloromethane
(10 mL) and to the solution pyridinium p-tolylsulfonate
(PPTS) (75 mg, 0.30 mmol) was added and stirred at room
temperature for 1 h. The reaction mixture was concentrated
in vacuo and the residue was chromatographed on silica gel
and eluted with AcOEt–hexane (1:20) to afford 12a as
colorless crystals, melted at 46.5–47.08C (from MeOH), in
75.4% isolated yield. 1H NMR (400 MHz, CDCl3): dH 0.97 (s,
9H), 1.01 (s, 6H), 3.81 (s, 3H), 3.97 (s, 2H), 6.66 (s with fine
coupling, 1H), 6.70 (d with fine coupling, J¼7.3 Hz, 1H), 6.80
(dd with fine coupling, J¼8.3, 2.4 Hz, 1H), 7.19 (dd, J¼8.3,
3.1.17. 5-tert-Butyl-4-(3-hydroxynaphthalen-2-yl)-3,3-
dimethyl-2,3-dihydrofuran (13b). Similarly to the prep-
aration of 13a from 12a, the demethylation of 5-tert-butyl-
4-(7-methoxynaphthalen-2-yl)-3,3-dimethyl-2,3-dihydro-
furan (12b) was carried out to give 13b as colorless crystals,
melted at 186.0–188.08C, in 93.0% isolated yield. 1H NMR
(400 MHz, CDCl3): dH 0.97 (s, 9H), 1.04 (s, 6H), 4.02 (s,
2H), 7.07 (dd, J¼8.8, 2.4 Hz, 1H), 7.09–7.12 (m, 2H), 7.40
(broad s, 1H), 7.68 (d, J¼8.3 Hz, 1H), 7.74 (d, J¼8.8 Hz,
1H). IR (KBr): 3358, 3058, 2862, 2869, 1509, 1216 cm21
.
Mass (EI) (m/z, %): 296 (Mþ, 57), 281 (100), 225 (27).
HRMS (EI): 296.1773, calcd for C20H24O2 296.1776.
7.3 Hz, 1H). IR (KBr): 2959, 2872, 1665, 1589, 1266 cm21
.
Mass (EI) (m/z, %): 260 (Mþ, 41), 245 (100), 189 (30), 187
(11). HRMS (EI): 260.1769, calcd for C17H24O2 260.1776.
3.1.18. 5-tert-Butyl-4-(4-hydroxyphenyl)-3,3-dimethyl-
2,3-dihydrofuran (13c). Similarly to the preparation of
13a from 12a, the demethylation of 5-tert-butyl-4-(4-
methoxyphenyl)-3,3-dimethyl-2,3-dihydrofuran (12c) was
3.1.14. 5-tert-Butyl-4-(7-methoxynaphthalen-2-yl)-3,3-
dimethyl-2,3-dihydrofuran (12b). Similarly to the

N. Watanabe et al. / Tetrahedron 59 (2003) 4811–4819
4817
carried out to give 13c as colorless granules, melted at
195.0–196.08C (from hexane–AcOEt), in 93.0% isolated
yield. 1H NMR (400 MHz, CDCl3): dH 0.95 (s, 9H), 0.98 (s,
6H), 3.96 (s, 2H), 4.59 (s, 1H), 6.75 (d with fine coupling,
J¼8.5 Hz, 2H), 6.96 (d with fine coupling, J¼8.5 Hz, 2H).
nyl]-4,4-dimethyl-2,6,7-trioxabicyclo[3.2.0]heptane
(4a). A solution of 5-tert-butyl-4-[(3-tert-butyldimethyl-
siloxy)phenyl]-3,3-dimethyl-2,3-dihydrofuran (7a) (100 mg)
and TPP (1 mg) in dichloromethane (10 mL) was irradiated
with 940 W Na-lamp under oxygen atmosphere at 2788C
for 1 h. The photolysate was concentrated and chromato-
graphed on silica gel (Fuji silisia, NH-DM1020). Elution
with hexane gave the desired dioxetane 4a as colorless
granules, melted at 42.0–43.08C (from hexane–AcOEt), in
83.0% yield. 1H NMR (400 MHz, CDCl3): dH 0.18 (s, 3H),
0.19 (s, 3H), 0.84 (s, 3H), 0.95 (s, 9H), 0.98 (s, 9H), 1.07 (s,
3H), 3.93 (d, J¼8.3 Hz, 1H), 4.54 (d, J¼8.3 Hz, 1H), 6.80
(ddd, J¼8.3, 2.4, 1.0 Hz, 1H), 6.89 (broad s, 1H), 6.94(broad
d, J¼7.8 Hz, 1H), 7.22 (dd, J¼8.3, 7.8 Hz, 1H). 13C NMR
(100 MHz, CDCl3):dC 24.3, 15.5, 18.2, 24.0, 24.4, 25.7, 36.2,
45.6, 77.6, 101.6, 118.8, 119.4, 120.0, 121.0, 128.3, 136.8,
155.1. IR (KBr): 2959, 2893, 2861, 1583, 1248 cm21. Mass
(EI)(m/z, %):360(Mþ232, 13),345(11), 335(14), 279(100),
235 (885), 159 (69). CIMS: MHþ 393. HRMS (EI): 360.2467,
calcd for C22H36O2Si 360.2485.
IR (KBr): 3377, 2970, 2871, 1610, 1512, 1259, 1098 cm21
.
Mass (EI) (m/z,%): 246 (Mþ, 55), 231 (100), 175 (28).
HRMS (EI): 246.1609, calcd for C16H22O2 246.1620.
3.1.19. 5-tert-Butyl-4-[(3-tert-butyldimethylsiloxy)phe-
nyl]-3,3-dimethyl-2,3-dihydrofuran (7a). 5-tert-Butyl-4-
(3-hydroxyphenyl)-3,3-dimethyl-2,3-dihydrofuran
(13a)
(212 mg, 0.86 mmol) was stirred together with imidazole
(120 mg, 1.77 mmol) and tert-butyldimethylsilyl chloride
(285 mg, 1.89 mmol) in DMF (3 mL) under nitrogen
atmosphere at 08C for 1 h. The reaction mixture was poured
into NaCl aq. solution and extracted with AcOEt. The
organic layer was washed with water, dried over MgSO4,
and concentrated in vacuo. The residue was chromato-
graphed on silica gel and eluted with AcOEt–hexane (1:20)
1
to give 7a as a colorless oil in 94.7% yield (293 mg). H
NMR (400 MHz, CDCl3): dH 0.18 (s, 6H), 0.96 (s, 9H), 0.98
(s, 9H), 1.00 (s, 6H), 3.96 (s, 2H), 6.60 (s with fine coupling,
1H), 6.70 (d with fine coupling, J¼7.3 Hz, 1H), 6.74 (ddd,
J¼8.3, 2.4, 1.0 Hz, 1H), 7.12 (dd, J¼8.3, 7.3 Hz, 1H). 13C
NMR (100 MHz, CDCl3): dC 24.3, 18.3, 25.7, 26.0, 29.1,
33.4, 46.9, 81.2, 116.4, 118.4, 123.4, 124.9, 128.2, 137.1,
154.8, 157. IR (liquid film): 2957, 2860, 1575, 1477, 1273,
1117 cm21. Mass (EI) (m/z, %): 360 (Mþ, 35), 345 (100), 289
(17). HRMS (EI): 360.2470, calcd for C22H36O2Si 360.2485.
3.1.23. 1-tert-Butyl-5-[(7-tert-butyldimethylsiloxy)-
naphthalen-2-yl]-4,4-dimethyl-2,6,7-trioxabicyclo-
[3.2.0]heptane (4b). Similarly to the preparation of 4a from
7a, the singlet oxygenation of 5-tert-butyl-4-[(7-tert-
butyldimethylsiloxy)naphthalen-2-yl]-3,3-dimethyl-2,3-
dihydrofuran (7b) was carried out to give as colorless
granules, melted at 110.0–111.08C (from MeOH), in 93.6%
isolated yield. 1H NMR (400 MHz, CDCl3): dH 0.27 (s, 6H),
0.88 (s, 3H), 0.97 (s, 9H), 1.03 (s, 9H), 1.13 (s, 3H), 3.98 (d,
J¼8.1 Hz, 1H), 4.60 (d, J¼8.1 Hz, 1H), 7.10 (dd, J¼8.8,
2.1 Hz, 1H), 7.10 (dd, J¼8.8, 2.1 Hz, 1H), 7.21 (d,
J¼2.1 Hz, 1H), 7.29 (broad d, J¼8.2 Hz, 1H), 7.70–7.75
(m, 3H). 13C NMR (100 MHz, CDCl3): dC 24.1, 15.7, 18.4,
24.3, 24.7, 25.8, 36.4, 46.0, 77.8, 102.2, 115.2, 121.2, 122.6,
124.8, 126.1, 128.1, 128.8, 133.0, 133.8, 153.8. IR (KBr):
2959, 2895, 2861, 1630, 1603, 1255 cm21. Mass (EI) (m/z,
%): 442 (Mþ, 15), 329 (17), 285 (100). HRMS (EI):
442.2526, calcd for C26H38O4Si 442.2539.
3.1.20. 5-tert-Butyl-4-[(7-tert-butyldimethylsiloxy)-
naphthalen-2-yl]-3,3-dimethyl-2,3-dihydrofuran
(7b).
Similarly to the preparation of 7a from 13a, the silylation
of 5-tert-butyl-4-(7-hydroxynaphthalen-2-yl)-3,3-dimethyl-
2,3-dihydrofuran (13b) was carried out to give 7b as
colorless granules, melted at 101–1028C (from MeOH), in
97.7% yield. 1H NMR (400 MHz, CDCl3): dH 0.26 (s, 6H),
0.97 (s, 9H), 1.03 (s, 9H), 1.05 (s, 6H), 4.02 (s, 2H), 7.04 (dd,
J¼8.8, 2.4 Hz, 1H), 7.10 (dd, J¼8.3, 1.7 Hz, 1H), 7.15 (d,
J¼2.4 Hz, 1H), 7.41 (broad s, 1H), 7.67 (d, J¼8.3 Hz, 1H),
7.70 (d, J¼8.8 Hz, 1H). 13C NMR (100 MHz, CDCl3): dC
24.1, 18.4, 25.8, 26.2, 29.4, 33.6, 47.2, 81.3, 114.7, 116.6,
121.5, 126.3, 127.8, 128.2, 128.6, 128.8, 133.6, 134.1, 153.3,
3.1.24. 1-tert-Butyl-5-[(4-tert-butyldimethylsiloxy)phe-
nyl]-4,4-dimethyl-2,6,7-trioxabicyclo[3.2.0]heptane
(4c). Similarly to the preparation of 4a from 7a, the singlet
oxygenation
of
5-tert-butyl-4-[(4-tert-butyldimethyl-
157.8. IR (KBr): 2956, 2862, 1668, 1630, 1599, 1248 cm21
.
siloxy)phenyl]-3,3-dimethyl-2,3-dihydrofuran (7c) was car-
ried out to give 4c as colorless granules, melted at 79.0–
Mass (EI) (m/z, %): 410 (Mþ, 65), 395 (100), 353 (12), 339
(21). HRMS (EI): 410.2624, calcd for C26H38O2Si 410.2641.
1
80.08C (from MeOH), in 74.7% isolated yield. H NMR
(400 MHz, CDCl3): dH 0.21 (s, 6H), 0.83 (s, 3H), 0.93 (s,
9H), 0.99 (s, 9H), 1.06 (s, 3H), 3.92 (d, J¼8.3 Hz, 1H), 4.53
(d, J¼8.3 Hz, 1H), 6.84 (d, J¼8.8 Hz, 2H), 6.93 (d,
J¼8.8 Hz, 2H). 13C NMR (100 MHz, CDCl3): dC 24.2,
15.6, 18.4, 24.1, 24.6, 25.8, 36.3, 45.5, 77.5, 101.8, 119.0,
120.7, 127.7, 127.9, 154.9. IR (KBr): 2957, 2891, 1610,
1263 cm21. Mass (EI) (m/z, %): 336 (Mþ256 (Me2-
CvCH2, 56), 235 (100). CIMS: MHþ 393. HRMS (EI):
336.1762, calcd for C18H28O4Si 336.1757.
3.1.21. 5-tert-Butyl-4-[(4-tert-butyldimethylsiloxy)phe-
nyl]-3,3-dimethyl-2,3-dihydrofuran (7c). Similarly to the
preparation of 7a from 13a, the silylation of 5-tert-butyl-4-
(4-hydroxyphenyl)-3,3-dimethyl-2,3-dihydrofuran (13c)
was carried out to give 7c as a colorless oil in 89.5%
yield. 1H NMR (400 MHz, CDCl3): dH 0.20 (s, 6H), 0.94 (s,
9H), 0.98 (s, 15H), 3.96 (s, 2H), 6.75 (d with fine coupling,
J¼8.5 Hz, 2H), 6.93 (d with fine coupling, J¼8.5 Hz, 2H).
13C NMR (100 MHz, CDCl3): dC 24.2, 18.4, 25.8, 26.0,
29.3, 33.5, 46.7, 81.1, 116.1, 118.9, 128.4, 132.4, 154.1,
3.2. Isolation of an emitter as a neutral form from the
spent reaction mixture of CIEEL-decay of 1-tert-butyl-5-
[(tert-butyldimethylsiloxy)aryl]-4,4-dimethyl-2,6,7-
trioxabicyclo [3.2.0]heptane (4a–4c)
157.5. IR (liquid film): 2955, 2929, 1507, 1259, 1118 cm21
.
Mass (EI) (m/z, %): 360 (Mþ, 83), 345 (100), 289 (21).
HRMS (EI): 360.2481, calcd for C22H36O2Si 360.2485.
3.1.22. 1-tert-Butyl-5-[(3-tert-butyldimethylsiloxy)phe-
General procedure. To a solution of 1-tert-butyl-5-[(tert-

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N. Watanabe et al. / Tetrahedron 59 (2003) 4811–4819
butyldimethylsiloxy)aryl]-4,4-dimethyl-2,6,7-trioxabi-
cyclo[3.2.0]heptane (4a–4c) (0.1 mmol) in DMSO (2 mL),
TBAF in DMSO (1.0£1021 mol dm23, 4 mL) was added
and stirred at room temperature. The reaction mixture was
poured into NaCl aq. solution and extracted with AcOEt.
The organic layer was washed with water, dried over
MgSO4, and concentrated in vacuo. The residue was
chromatographed on silica gel and eluted with AcOEt–
hexane (1:4) to give the corresponding ketoester (14a–14c):
89% yield for 14a, 93% yield for 14b, and 49% yield for
14c.
measurement. The intensity of the light emission time-
course was recorded and processed according to first-order
kinetics. The total light emission was estimated by
comparing it with that of an adamantylidene dioxetane
(1), whose chemiluminescent efficiency F CIEEL has been
reported to be 0.29 and was used here as a standard.5
3.5. Fluorescence measurement of 3-(3-hydroxyaryl)-
2,2-dimethyl-3-oxopropan-1-yl 2,2-dimethylpropanoate
(14a and 14b)
Freshly prepared solution of 2.05–2.10£1025 mol dm23 of
14a or 14b and of 1.0£1022 mol dm23 of TBAF in DMSO
was transferred to a quartz cell (10£10£50 mm3) and the
latter placed in the spectrometer, which was thermostated
with stirring at 258C. Thus, the fluorescence spectra of 14a
and 14b were measured and their fluorescence efficiencies
(F fl) were estimated using quinine bisulfate for 14a or
using fluorescein for 14b as a standard.24
3.2.1. 3-(3-Hydroxyphenyl)-2,2-dimethyl-3-oxopropan-
1-yl 2,2-dimethylpropanoate (14a). As colorless granules
1
melted at 69.0–70.08C (from hexane–AcOEt). H NMR
(400 MHz, CDCl3): dH 1.14 (s, 9H), 1.37 (s, 6H), 4.26 (s,
2H), 6.95 (dd, J¼8.1, 2.6 Hz, 1H), 7.09 (s with fine
coupling, 1H), 7.19 (d with fine coupling, J¼7.7 Hz, 1H),
7.27 (dd, J¼8.1, 7.7 Hz, 1H). 13C NMR (125 MHz, CDCl3):
dC 23.2, 27.0, 38.8, 47.9, 70.5, 114.4, 118.5, 119.3, 129.5,
139.6, 155.9, 178.6, 207.0. IR (KBr): 3319, 2981, 1730,
1668, 1594, 1266 cm21. Mass (EI) (m/z, %): 278 (Mþ, 6),
222 (17), 121 (100), 57 (27). HRMS (ESI): 301.1408, calcd
for C16H22O4Na (MþNaþ) 301.1416.
Acknowledgements
The authors gratefully acknowledge financial assistance
provided by a Grant-in aid (No. 13640546 and No.
14540506) for Scientific Research by the Ministry of
Education, Science, Sports, and Culture of the Japanese
Government.
3.2.2. 3-(7-Hydroxynaphthalen-2-yl)-2,2-dimethyl-3-
oxopropan-1-yl 2,2-dimethylpropanoate (14b). Colorless
granules, melted at 137.0–138.08C (from hexane–AcOEt).
1H NMR (400 MHz, CDCl3): dH 1.14 (s, 9H), 1.43 (s, 6H),
4.32 (s, 2H), 5.31 (s, 1H), 7.16–7.21 (m, 1H), 7.19 (s, 1H),
7.54 (dd, J¼8.5, 1.7 Hz, 1H), 7.76 (d, J¼8.1 Hz, 1H), 7.78
(d, J¼8.5 Hz, 1H), 7.96 (s with fine coupling, 1H). 13C
NMR (125 MHz, CDCl3): dC 23.4, 27.1, 38.8, 48.0, 70.6,
110.5, 119.9, 121.8, 126.2, 127.9, 129.5, 129.7, 133.6,
136.4, 154.4, 178.4, 207.3. IR (KBr): 3363, 2970, 2873,
1708, 1667, 1629, 1600 cm21. Mass (EI) (m/z, %): 328
(Mþ, 15), 272 (30), 171 (100), 143 (17), 57 (10). HRMS
(ESI): 351.1588, calcd for C20H24O4Na (MþNaþ)
351.1572.
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