Allenyl(vinyl)methane photochemistry. Photochemistry of γ-allenyl-substituted α,β-unsaturated enone derivatives

Article abstract of DOI:10.1016/S0040-4020(02)00856-6

The photolyses of the γ-allenyl-substituted alkylidenecycloalkanones underwent mainly E-Z geometric isomerization; several enones gave pyrans by the photochemical intramolecular oxa-Diels-Alder reaction and bicyclo[2.1.0]pentanes by the intramolecular [2+2] cycloaddition. The photolyses of the γ-(3-methyl-1,2-butadienyl)-substituted 3-alkylidenepenta-2,4-diones led to bicyclo[2.1.0]pentane, while the γ-(1,2-propadienyl-substituted) 3-alkylidenepenta-2,4-diones underwent intramolecular [2+2] cycloaddition and intramolecular oxa-Diels-Alder reaction.

Full text of DOI:10.1016/S0040-4020(02)00856-6

Tetrahedron 58 (2002) 7681–7689
Allenyl(vinyl)methane photochemistry. Photochemistry of
g-allenyl-substituted a,b-unsaturated enone derivatives
*
Takashi Tsuno, Masato Yoshida, Tetsu Iwata and Kunio Sugiyama
Department of Applied Molecular Chemistry, College of Industrial Technology, Nihon University, Narashino, Chiba 275-8575, Japan
Received 7 June 2002; accepted 13 July 2002
Abstract—The photolyses of the g-allenyl-substituted alkylidenecycloalkanones underwent mainly E–Z geometric isomerization; several
enones gave pyrans by the photochemical intramolecular oxa-Diels–Alder reaction and bicyclo[2.1.0]pentanes by the intramolecular [2þ2]
cycloaddition. The photolyses of the g-(3-methyl-1,2-butadienyl)-substituted 3-alkylidenepenta-2,4-diones led to bicyclo[2.1.0]pentane,
while the g-(1,2-propadienyl-substituted) 3-alkylidenepenta-2,4-diones underwent intramolecular [2þ2] cycloaddition and intramolecular
oxa-Diels–Alder reaction. q 2002 Elsevier Science Ltd. All rights reserved.
1. Introduction
undergo interesting photoreactions by an interaction
between the allenyl and alkenoyl chromophores.
The photochemical intramolecular [2þ2] cycloaddition of
a,b-unsaturated enones linked to an alkene by hydrocarbon
chains is well-known, has been extensively investigated,
and has found widespread application in organic synthesis.1
An allene is a good alkene that undergoes photochemical
intramolecular [2þ2] cycloaddition.1–3 The syntheses of
natural products by the intramolecular [2þ2] cycloaddition
of allenes with a,b-unsaturated enones has been reported.1,3
In this paper, we wish to report the photochemistry of the
allenyl(alkenoyl)methanes 1–6 (Scheme 1).
2. Results
2.1. Preparation of the enones (1–6)
In the photochemistry of g-allenyl-substituted a,b-unsatu-
rated ketones, except for our communication,4 there is only
one report by Jeger et al., but its content is a mere note.5 On
the other hand, in the photochemistry of divinylmethane
compounds, g-vinyl-substituted a,b-unsaturated esters6,7
and nitriles6,8 underwent regioselective di-p-methane
rearrangement by multiplicity control, while other photo-
reactions in addition to the di-p-methane rearrangement for
the g-vinyl-substituted a,b-unsaturated ketones took
place.9,10 Previously, we reported the photochemistry of
allenyl(vinyl)methanes in which one vinyl is an a,b-
unsaturated ester11,12 or an a,b-unsaturated nitrile chromo-
phore.11 These compounds formed an intramolecular CT
complex, and the excited state of each allenyl chromophore,
vinyl chromophore, and CT complex, underwent different
photoreactions. The energy levels and lifetimes of the n!pp
and p!pp and the electron deficiency of the CvC moiety
of the a,b-unsaturated ketones differ from those of the a,b-
unsaturated esters. Thus we have considered that the newly
prepared g-allenyl-substituted a,b-unsaturated ketones
We first prepared the enones 1–4 by the aldol condensation
of allenic aldehydes with cycloalkanones. Because the
condensation with cyclopentanone using NaOMe as a base
catalyst afforded a complex mixture, the isolation of 1 or 2
failed. On the other hand, 3 and 4 were obtained by
purification using silica gel chromatography in 13 and 17%
yields, respectively (Scheme 2). Kelleher et al.13 have
reported that a,b-unsaturated enones were prepared in good
yields by the condensation using lithium iodide as a base
catalyst. So we applied Kelleher’s method for the
condensation of allenic aldehydes with cyclopentanone.
The enones 1 and 2 were obtained in satisfactory purity but
in low yields (Scheme 3).
Keywords: photochemistry; allenes; enones; Diels–Alder reactions;
cycloadditions.
*
Corresponding author. Tel.: þ81-47-474-2569; fax: þ81-47-474-2579;
e-mail: t5tuno@cit.nihon-u.ac.jp
Scheme 1.
0040–4020/02/$ - see front matter q 2002 Elsevier Science Ltd. All rights reserved.
PII: S0040-4020(02)00856-6

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T. Tsuno et al. / Tetrahedron 58 (2002) 7681–7689
Scheme 2.
Scheme 3.
Scheme 4.
isolated cis-adduct 11 was readily isomerized to the trans-
1
one 12 by observation of H NMR. The photochemical
Table 1. Photolyses of 1–6
isomerization of the (E ) and (Z )-enones 1, 2, 7, and 9 was
analyzed by GLC. Each photolysis was found to form
polymeric materials; hence, the total ratio of composition of
the substrate and the intramolecular photoproducts
decreased with prolongation of irradiation time. An
induction period for the isomerization of the (E )-form 1
or 2 to the pyran 8 or 10 was found; whereas, in the direct
photolyses of the (Z )-forms 7 and 9, 8 and 10 were initially
formed.
Enone
Time (h)
Products (isolated yields (%))
1
2
3
6
6
1
18
1
9
7 (8)
9 (6)
13 (51)
(8)
15 (51)
16 (7)
8 (25)
10 (5)
11 (11)
18 (2)
12 (17)
14 (6)
4
5
6
17 (10)
19 (22)
4
The diketones 5 and 6 were prepared by Knoevenagel
condensation of allenic aldehydes with sodium 2,4-penta-
nedionate using the procedure of Lehnert14 (Scheme 4).
For the direct photolyses of 3 and 4, the E–Z geometric
isomerization mainly occurred, and these geometric isomers
were observed in an ca. E/Z¼1:9 ratio as a steady state.
Upon irradiation for 1 h, (Z)-isomers 13 and 15 were both
obtained in 51% isolated yields (Table 1). During the
prolonged irradiation of 3 or 4, the composition of the (E )
and (Z)-forms gradually decreased due to their polymeriz-
ation and the formation of complicated photoproducts. In
the case of 3 upon irradiation for 18 h, the (Z)-form 13 and
pyran 14 were obtained (Table 1). Because the pyran 14 was
an unstable product especially under acidic condition,
2.2. Photochemistry of the enones (1–4)
A solution of 1 in hexane was irradiated using a 100 W high-
pressure mercury lamp with a pyrex jacket to give the (Z )-
form 7 and pyran 8 (Table 1, Scheme 5), and considerable
polymeric materials were further formed. A similar
photolysis of 2 gave the pyran 10, [2þ2] cycloadducts 11
and 12, and (Z )-form (9) (Table 1). It was found that the
Scheme 5.

T. Tsuno et al. / Tetrahedron 58 (2002) 7681–7689
7683
Table 2. Quantum yields for the isomerization in the direct photolyses of
the enones
isolation from the mixture of the photoproducts by silica gel
chromatography failed. However, when activated aluminum
oxide (neutral) chromatography was carried out, we
accomplished the separation of 14 from the mixture of the
photoproducts.
Enone
Solvent
Quantum yields
a
b
Fcy
c
Foxa
Fge
1
Hexane
Acetonitrile
Hexane
Acetonitrile
Hexane
Acetonitrile
Hexane
Acetonitrile
Hexane
Acetonitrile
Hexane
Acetonitrile
Hexane
Acetonitrile
Hexane
Acetonitrile
Hexane
,0.0001
,0.0001
,0.0001
,0.0001
,0.0001
,0.0001
0.24
0.30
0.19
0.23
0.29
0.31
0.34
0.43
0.18
0.15
0.15
0.13
0.12
0.10
0.10
0.11
The quantum yields for the isomerization of the enones 1–4,
7, 9, 13, and 15 are described in Table 2. Quantum yields for
the isomerization of the (E)-enones 1, 2, and 4 to the pyrans
8, 10, and 14 were only trace amounts, while those of the
(Z )-forms 7, 9 and 13 were measurable values. Table 3
shows the quantum yields for isomerization in the
acetophenone-sensitization of the enones 1–4, 7, 9, 13,
and 15. Acetophenone (ET¼310 kJ mol21) affected the
intramolecular isomerization. Though the compounds 1 and
2 were non phosphorescent, 7 and 9 were observed to show
phosphorescent emissions in an EPA (ether/isopentane/
ethanol¼5:5:2) matrix at 77 K, and their triplet energies
were both estimated to be 280 kJ mol21 by 0–0 bands.
However, when 2-methyl-1,3-butadiene was used as a
quencher, quenching effects for each isomerization were not
observed.
2
0.011
0.023
3
4
7
0.049
0.033
0.0072
0.011
0.012
0.0066
9
0.010
0.021
13
15
5
0.0049
0.0047
0.0049
0.0045
0.11
Acetonitrile
Hexane
Acetonitrile
6
0.12
A 450 W high-pressure mercury lamp with a combination of K2CrO4
solution and a pyrex glass filter was used as a 313 nm radiation source, and
the light intensity was determined by stilbene actinometry.
2.3. Photochemistry of the diketones (5 and 6)
a
The direct photolysis of 5 in hexane gave the pyran 16,
cycloadduct 17, and cyclopentene 18 in 7, 10, and 2%
isolated yields, respectively (Scheme 6). In a similar
photolysis of 6, intramolecular [2þ2] cycloaddition
preferentially proceeded to afford the intramolecular
[2þ2] cycloadduct 19 in 22% isolated yield. Quantum
yields for the isomerization of the diketones 5 and 6 are
described in Tables 2 and 3. Few solvent effects were found
Quantum yield for the intramolecular oxa-Diels–Alder reaction.
Quantum yield for the intramolecular [2þ2] cycloaddition.
b
c
Quantum yield for the E!Z or Z!E geometric isomerization.
Table 3. Quantum yields for the isomerization in the acetophenone-
sensitized photolyses of the enones
on the isomerization. Acetophenone (ET¼310 kJ mol21
)
Enone
Quantum yields
sensitized the intramolecular [2þ2] cycloaddition alone,
and benzophenone (ET¼288 kJ mol21) also showed a
sensitizing effect on the reaction. However, neither
4-phenylacetonaphthone (ET¼256 kJ mol21) nor 2-acetyl-
naphthalene (ET¼249 kJ mol21) had a sensitizing effect.
Moreover, quenching effects by 2-methyl-1,3-butadiene on
the isomerization of the enones were not observed. The
quantum yield for the formation of 18 under the direct
photolysis of 5 was only a trace amount. Although we
considered that compound 18 was derived from the
photolysis of the intramolecular [2þ2] cycloadduct 17, the
direct photolysis of the isolated 17 did not lead to 18.
a
b
Fcy
c
Foxa
Fge
1
2
3
4
7
9
13
15
5
,0.0001
,0.0001
,0.0001
0.27
0.22
0.26
0.26
0.32
0.22
0.080
0.053
0.012
0.038
0.014
0.0084
0.017
,0.0001
0.017
0.27
6
A 450-W high-pressure mercury lamp with a combination of K2CrO4
solution and a pyrex glass filter was used as a 313 nm radiation source, and
the light intensity was determined by stilbene actinometry. Acetophenone:
conc. 1.20 mol dm23. A hexane solution of the enones (0.01 mol dm23) in a
pyrex tube was irradiated under an argon atmosphere at room temperature.
3. Discussion
a
Quantum yield for the intramolecular oxa-Diels–Alder reaction.
Quantum yield for the intramolecular [2þ2] cycloaddition.
3.1. Intramolecular [212] cycloaddition
On the basis of the photochemistry of g-allenyl-substituted
b
c
Quantum yield for the E!Z or Z!E geometric isomerization.
Scheme 6.

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T. Tsuno et al. / Tetrahedron 58 (2002) 7681–7689
Table 4. Calculated frontier orbital energies, HOMO and its coefficients of model compounds 20–26
Compound
HOMO (eV)
MO coefficient
C1
C2
C3
O
20
21
22
23
24
25
26
29.82
29.46
210.03
210.05
29.94
20.21
0.60
0.01
0.01
0.04
0.10
0.59
0.60
0.65
20.18
20.60
20.60
20.61
20.60
20.31
20.60
20.56
20.60
20.61
20.46
0.23
0.23
0.22
0.19
0.28 (E)
0.46 (Z )
210.06
210.60
0.19 (E)
0.18 (Z)
a,b-unsaturated esters and nitriles, we have obtained the
following knowledge:11,12
estimated triplet energies, it was expected that 2-methyl-
1,3-butadiene could be efficient in the isomerization of the
enones, though quenching effects were not found. Hence, it
is considered that the isomerizations of these enones involve
a singlet pathway.
1. Because the HOMO of a 1,2-propadienyl group lies at the
C2–C3 moiety and the MO coefficients of C3 is higher
value than that of the C2 (Table 4), the 1,2-propadienyl-
substituted esters undergo more ineffective intra-
molecular [2þ2] cycloaddition than the 3-methyl-1,2-
propadienyl-substituted esters.
2. The allenyl(vinyl)methanes initially bond between the
allene center carbon and the a-carbon of the a,b-
unsaturated ester or the nitrile moiety to give cyclo-
pentane-1,3-dienyl radicals.
Though we would have expected that the 3-methyl-1,2-
butadienyl-substituted alkylidenecyclohexanones 4 and 15
undergoes intramolecular [2þ2] cycloaddition, energy-
wasting E–Z geometric isomerization mainly took place
and prolonged irradiation produced polymers. A similar
tendency for the preferential E–Z geometric isomerization
was recognized in the photolyses of 3 except that pyran 14
was obtained under prolonged irradiation. We then
performed PM3 MO calculations for the ground state of
20–26 as models of the chromophores of 1–7, 9, 13, and 15
(Table 4). By the MO coefficients of the model compounds,
it seems that the interaction between the a-carbon of the
enone and the center carbon of the allene is possible.
However, the intramolecular [2þ2] cycloaddition of 1–4, 7,
9, 13, and 15 was hardly prohibited. This is considered
that steric hindrance by the alkyl-substituent at the
a-position of the enone moiety makes it hard for the
intramolecular [2þ2] cycloaddition to occur: i.e. over-
lapping between the MO’s of the center carbon of the
allene and of the a-carbon of these exo-cycloalkenones
will be blocked. Especially, because the HOMO of the
enones 1 and 3 lies at the 2,3-CvC moiety in the 1,2-
propadienyl group and the MO at the 3-position has a larger
coefficient than that at the 2-position (Table 4), no
intramolecular [2þ2] cycloaddition takes place. In the
case of the photochemistry of the 1,2-propadienyl-substi-
tuted diketone 5, the intramolecular [2þ2] cycloadduct 17
was obtained. Because the HOMO of 26 lies at a lower level
than that of the exo-cycloalkenones 22–25 due to two
acetyl-substitutions at the geminal position on the vinyl
moiety (Table 4), it is considered that some MO interaction
between the a-carbon and the center carbon of the allene in
5 occurs. On the other hand, in the case of the
photochemistry of the diketone 6, because the HOMO of
21 lies at the 1,2-CvC moiety in the allenyl group, the
3. The intramolecular [2þ2] cycloaddition occurs via both
singlet and triplet excited states.
4. The triplet intramolecular [2þ2] cycloaddition occurs
from the excited state of the a,b-unsaturated ester or the
nitrile moiety.
Jeger et al.5 reported that the 3-methyl-1,2-butadienyl-
substituted alicyclic a,b-unsaturated enones readily under-
went the intramolecular [2þ2] cycloaddition. Judging by
the quantum yields for the isomerization of the exo-
cycloalkenones 1–4, 7, 9, 13, and 15, the E–Z geometric
isomerization mainly takes place, and the intramolecular
[2þ2] cycloaddition takes place as a side reaction in the
photolyses of the enones 2 and 9. On the other hand, the
diketones 5 and 6 gave the intramolecular [2þ2] cyclo-
adducts 17 and 19, but the quantum yield of 6–19 is a
several tens of times greater than that of 5–17 (Tables 2 and
3). Such tendencies are analogous to the photochemistry of
the g-allenyl-substituted a,b-unsaturated esters;11 hence, it
is obvious that the HOMO in the allenyl moiety contributes
greatly to the photochemical intramolecular [2þ2] cyclo-
addition of these enones. The triplet energies of the enones 7
and 9 are ca. 280 kJ mol21, and further, those of the
diketones 5 and 6 are estimated to be in range of 280–
260 kJ mol21. These estimated triplet energies are close to
the reported triplet energies of the a,b-unsaturated
enones.15 Therefore, the intramolecular [2þ2] cyclo-
addition by the triplet sensitization occurs from the triplet-
excited state of the enone moiety. Furthermore, due to the
intramolecular
preferentially.
[2þ2]
cycloaddition
progresses

T. Tsuno et al. / Tetrahedron 58 (2002) 7681–7689
7685
Scheme 7.
3.2. Intramolecular oxa-Diels–Alder reaction
photochemical intramolecular oxa-Diels–Alder reaction of
the enone with the allene is the first example.
In the photochemistry of these enones, except for 4 and 15,
the formation of pyrans by an intramolecular oxa-Diels–
Alder reaction was found. It is obvious that the pyrans 8, 10,
and 14 were derived from the photoreaction of the Z-enones
by GLC analyses and the quantum yields. These results also
suggest that an excited state of a Z-acetyl moiety in the
diketone 5 afforded the pyran 16. We have found the
formation of the pyran-type compounds as by-products in
some allenyl(vinyl)methane photochemistry,11a–d,12 and
further, it has been reported that the photochemistry of
several alkenyl(alkenoyl)methane compounds (3,6-hepta-
dien-2-ones) afforded pyran compounds via the intra-
3.3. Formation of 18
Although we had considered that the cyclopentene 18 in the
direct photolysis of 5 was produced from a photoreaction of
the resulting bicyclo[2.1.0]pentane 17, the isolated 17 upon
direct irradiation did not afford 18. This result suggests that
the cyclopentene 18 was derived from the direct photolysis
of 5. Because the cyclopentene 18 is a by-product, the
detailed mechanism has not been fully clarified, but we
consider the following. The resulting cyclopentane-1,3-diyl
radical undergoes a 1,3-acyl rearrangement to give 18
(Scheme 8).
molecular oxa-Diels–Alder reaction.10 Such
a
photochemical oxa-Diels–Alder reaction initially causes
bonding between the excited oxygen of the carbonyl group
and the center carbon of the allene or the C7 of the
3,6-heptadien-2-ones to afford oxacycloheptane biradical
intermediates, followed by a ring closure to give the pyrans
(Scheme 7). The exo-cycloalkenones have a reasonable s-cis
conformation. In addition, the IR spectrum of the diketone 5
shows two types of carbonyl bands at 1712 and 1665 cm21
.
Scheme 8.
The former band suggests that either of the two acetyl
groups of 5 has an s-cis conformation with the CvC bond.
The five-membered enones undergo the oxa-Diels–Alder
reaction more efficiently than the six-membered enones. By
a PM3 molecular orbital calculation, the torsion angle about
the s-cis CvC–CvO single bond in the Z-forms of the six-
membered enones is ca. 708, while the five-membered
enones are nearly coplanar. These calculations were
supported by UV-absorption spectra of the (Z )-enones: i.e.
n–pp transitions of the (Z )-forms of the five-membered
enones showed more bathchromic shifts (ca. 30 nm) than
those of the six-membered enones.16 Therefore, because a
kink in the torsion angle in the CvC–CvO causes
differences in the overlapping between the MO’s of the
center carbon of the allene and of the excited oxygen of
the carbonyl group, we consider that ring-size effects on the
photochemical intramolecular oxa-Diels–Alder reaction
were found. Acetophenone sensitized the exo-cycloenones
to undergo the oxa-Diels–Alder reaction but did not affect
the diketone 5. Furthermore, the quenching effects for the
oxa-Diels–Alder reaction of the exo-cycloenones were not
found. In the photochemistry of the g-allenyl-substituted
a,b-unsaturated esters in our previous reports, each pyran-
type compound was obtained from direct photolysis only.
However, it is considered that the pyrans 8, 10, and 14 are
produced not only via a singlet pathway but also by a triplet
pathway.
4. Conclusion
Although the photolyses of the g-allenyl-substituted alkyl-
idenecycloalkanones mainly undergo E–Z geometric
isomerization, the intramolecular oxa-Diels–Alder reaction
and intramolecular [2þ2] cycloaddition take place in the
photolyses of several enones. The differences in these
reactivities cause the configuration of the CvC–CvO
moiety and the location of the HOMO in the allene moiety.
Because the vinyl moiety of the g-allenyl-substituted
3-alkylidene-2,4-pentadione is more electron-deficient
than the g-allenyl-substituted 3-alkylidenecycloalkanones,
the intramolecular [2þ2] cycloaddition occurs to give the
bicyclo[2.1.0]pentanes.
5. Experimental
5.1. General
The melting points were determined on a micro hot stage
(Yazawa) and are uncorrected. The NMR spectra were
measured in a CDCl3 or C6D6 solution using Bruker
Avance-400 and JEOL JNM-EX 90 spectrometers. The IR
spectra were obtained with a BIO-RAD FTS-60A spectro-
photometer. The MS and HRMS were obtained with a JEOL
JMS AX-500 and JEOL JMS-600H spectrometers. The
UV-absorption spectra were measured on a Shimadzu UV-
160A spectrophotometer. The phosphorescence spectra
were measured on a Hitachi F-3010 spectrofluorometer
attached to a phosphorescence-measurement apparatus.
Although the allenes have been employed as useful
dienophiles for dienes in the thermal Diels–Alder reaction17
or for heterodienes in the photochemical intermolecular
18
¨
cycloaddition, namely the Schoenberg reaction, such a

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T. Tsuno et al. / Tetrahedron 58 (2002) 7681–7689
Spectroscopic-grade hexane was washed with conc. H2SO4,
˚
distilled, and stored over 4A molecular sieves. Spectro-
scopic-grade acetonitrile, benzene, and commercial acetone
˚
were stored over 4A molecular sieves. The sensitizers used
were recrystallized or distilled.
Data for 3. Yield 13%; IR (neat) 1954 (CvCvC), 1689,
(CvO), 1612 (CvC) cm21; 1H NMR (CDCl3, 400 MHz) d
1.24 (6H, s, 2-Me£2), 1.64–1.78 (2H, m, CH2), 1.80–1.91
(2H, m, CH2), 2.44 (2H, t, J¼6.7 Hz, COCH2), 2.65 (2H, dt,
J¼1.9, 6.9 Hz, vCCH2), 4.80 (2H, d, J¼6.6 Hz,
CvCvCH2), 5.21 (1H, t, J¼6.6 Hz, CHvCvC), 6.53
(1H, t, J¼1.9 Hz, CHvC); 13C NMR (CDCl3, 100 MHz)
23.4 (t), 23.7 (t), 27.6 (t), 28.9 (2C, q, 2-Me), 35.6 (s, 2-C),
40.4 (t), 77.5 (t, 5-C), 99.2 (d, 3-C), 137.6 (s, sCv), 145.2
(d, 1-C), 202.2 (s), 206.5 (s); MS m/z (rel. intensity) 190
(Mþ, 0.7), 175 (98), 162 (21), 151 (100), 148 (23), 133 (22),
119 (36), 105 (50), 91 (45), 81 (30), 79 (38), 77 (30), 67
(28), 55 (36), 53 (28), 43 (32), 41 (60), 39 (34), 26 (21).
HRMS Found: m/z 190.1344. Calcd for C13H18O; M,
190.1358.
5.2. Preparation of 1–6
5.2.1. (E )-2-(2,2-Dimethyl-3,4-pentadienylidene)cyclo-
pentanone (1) and (E )-2-(2,2,5-trimethyl-3,4-hexa-
dienylidene)cyclopentanone (2). The aldol condensation
using lithium iodide described by Kelleher et al. was used.13
A benzene solution (100 cm3) of cyclopentanone (8.6 g,
0.10 mol), the allenic aldehyde (0.10 mol), and lithium
iodide (13.7 g, 0.10 mol) was stirred for 6 h at 608C under
an argon atmosphere. The reaction mixture was washed
with water (100 cm3), dried with MgSO4 and evaporated in
vacuo. The residual oil was chromatographed on silica gel
using 3% ether–hexane as an eluent to give 1 and 2.
Data for 4. Yield 17%; IR (neat) 1950 (CvCvC), 1689,
(CvO), 1611 (CvC) cm21; 1H NMR (CDCl3, 400 MHz) d
1.20 (6H, s, 2-Me£2), 1.68–1.75 (2H, m, CH2), 1.70 (6H, d,
J¼2.9 Hz, CvCvCMe2), 1.81–1.88 (2H, m, CH2), 2.43
(2H, t, J¼6.7 Hz, COCH2), 2.69 (2H, dt, J¼2.0, 6.8 Hz,
vCCH2), 5.03 (1H, septet, J¼2.6 Hz, CHvCvC), 6.55
(1H, t, J¼2.0 Hz, CHvC); 13C NMR (CDCl3, 100 MHz) d
20.5 (2C, q, 6-C), 23.4 (t), 23.6 (t), 27.6 (t), 29.1 (2C, q,
2-Me), 36.6 (s, 2-C), 40.4 (t), 98.3 (s, 5-C), 98.4 (d, 3-C),
137.2 (s, sCv), 146.1 (d, 1-C), 199.3 (s), 202.4 (s); MS m/z
(rel. intensity) 218 (Mþ, 15), 203 (91), 175 (22), 151 (100),
148 (49), 133 (34), 105 (26), 91 (29), 81 (38), 79 (28), 77
(21), 69 (27), 67 (44), 55 (40), 53 (21), 43 (40), 41 (70), 39
(22). HRMS Found: m/z 218.1651. Calcd for C15H22O; M,
218.1671.
Data for 1. Yield 9.1%; IR (neat) 1954 (CvCvC), 1721,
(CvO), 1640 (CvC) cm21; 1H NMR (CDCl3, 400 MHz) d
1.24 (6H, s, 2-Me£2), 1.91 (2H, pentaplet, J¼7.6 Hz,
CH2CH2CH2), 2.28 (2H, t, J¼7.8 Hz, COCH2), 2.74 (2H,
dt, J¼2.6, 7.3 Hz, vCCH2), 4.81 (2H, d, J¼6.6 Hz,
CvCvCH2), 5.19 (1H, t, J¼6.6 Hz, CHvCvC), 6.55
(1H, t, J¼2.6 Hz, CHvC); 13C NMR (CDCl3, 100 MHz) d
19.9 (t), 27.3 (t), 28.0 (2C, q, 2-Me), 36.2 (s, 2-C), 37.6 (t),
77.5 (t, 5-C), 98.7 (d, 3-C), 135.3 (s, sCv), 143.3 (d, 1-C),
206.6 (s, 4-C), 208.5 (s, CvO); MS m/z (rel. intensity) 176
(Mþ, 18), 161 (100), 148 (24), 137 (32), 133 (19), 120 (25),
119 (32), 105 (85), 95 (82), 91 (42), 79 (31), 77 (29), 67
(27), 53 (23), 41 (54), 32 (39), 26 (21). HRMS Found: m/z
176.1215. Calcd for C12H16O; M, 176.1202.
5.2.3. 3-Acetyl-5,5-dimethyl-3,6,7-octatrien-2-one (5)
and 3-acetyl-5,5,8-trimethyl-3,6,7-nonatrien-2-one (6).
The TiCl4 method described by Lehnert was used.14
A
Data for 2. Yield 5.4%; IR (neat) 1968 (CvCvC), 1722,
(CvO), 1639 (CvC) cm21; 1H NMR (CDCl3, 400 MHz) d
1.20 (6H, s, 2-Me£2), 1.71 (6H, d, J¼2.9 Hz,
CvCvCMe2), 1.90 (2H, pentaplet, J¼7.6 Hz, CH2CH2-
CH2), 2.27 (2H, t, J¼7.6 Hz, COCH2), 2.76 (2H, dt, J¼2.7,
7.3 Hz, vCCH2), 5.01 (1H, septet, J¼2.9 Hz, CHvCvC),
6.56 (1H, t, J¼2.7 Hz, CHvC); 13C NMR (CDCl3,
22.5 MHz) d 19.9 (t), 20.6 (2C, q, 6-C), 27.6 (t), 28.1 (2C,
q, 2-Me), 37.2 (s, 2-C), 37.6 (t), 97.5 (d, 3-C), 98.0 (s, 5-C),
134.9 (s, sCv), 144.1 (d, 1-C), 199.6 (s, 4-C), 208.5 (s,
CvO); MS m/z (rel. intensity) 204 (Mþ, 14), 189 (48), 161
(23), 148 (20), 138 (26), 137 (32), 134 (33), 95 (100), 67
(28), 55 (21), 41 (38). HRMS Found: m/z 204.1489. Calcd
for C14H20O; M, 204.1515.
solution of TiCl4 (11 cm3, 0.1 mol) in carbon tetrachloride
(25 cm3) was slowly added dropwise under argon to dry
THF (200 cm3) with stirring and cooling at 08C. To the
THF–TiCl4 suspension was added a mixture of the allenic
aldehyde (0.05 mol) and pyridine (8.0 cm3, 0.10 mol) in
THF (25 cm3) and further, sodium 1,3-pentanedionate
prepared by the reaction of sodium hydride (0.24 g,
0.10 mol) with 1,3-pentanedione (10.0 g, 0.10 mol) in
DMF (50 cm3) was added dropwise over 1 h. The mixture
was stirred for 24 h at room temperature and then quenched
with water (50 cm3). The layers were separated. The organic
layer was washed with sat. NaHCO3 solution and sat. NaCl
solution and then diluted with ether (50 cm3). The separated
aqueous layer was extracted with ether (50 cm3£2). The
combined ethereal layers were dried over MgSO4 and
evaporated in vacuo. The residue oil was distilled under
reduced pressure, and a collective fraction in the range of
80–908C (0.9 Torr, 1 Torr¼133.322 Pa) was chromato-
graphed on silica gel eluting with 10% EtOAc–hexane to
give 5 and 6.
5.2.2. (E )-2-(2,2-Dimethyl-3,4-pentadienylidene)cyclo-
hexanone (3) and (E )-2-(2,2,5-trimethyl-3,4-hexadienyl-
idene)cyclohexanone (4). A solution of cyclohexanone
(9.81 g, 0.10 mol), the allenic aldehyde (0.10 mol), and
NaOMe (2.0 g, 0.05 mol) in t-butyl alcohol (100 cm3) was
refluxed for 2 h under an argon atmosphere in a water
bath. The reaction mixture was evaporated under
reduced pressure, and the residual oil was acidified with
1.0 mol dm23 HCl solution and then extracted with CH2Cl2
(100 cm3). The organic fraction was dried with MgSO4
and evaporated in vacuo. The residue was chromatographed
on silica gel eluting with 3% EtOAc–hexane to give 3
and 4.
Data for 5. Yield 23%; IR (neat) 1955 (CvCvC), 1712
(CvO), 1665 (CvO), 1626 (CvC) cm21 1H NMR
;
(CDCl3, 400 MHz) d 1.26 (6H, s, 5-Me£2), 2.31 (3H, s,
MeCO), 2.32 (3H, s, MeCO), 4.83 (1H, d, J¼6.6 Hz,
CvCvCH), 4.84 (1H, d, J¼8.4 Hz, CvCvCH), 5.17 (1H,
dd, J¼6.6, 8.4 Hz, CHvCvC), 6.54 (1H, s, CHvC); 13C
NMR (CDCl3, 100 MHz) d 26.0 (q, 1-C), 28.3 (2C, q,

T. Tsuno et al. / Tetrahedron 58 (2002) 7681–7689
7687
5-Me£2), 32.8 (q, 1-C), 37.0 (s, 5-C), 78.0 (t, 8-C), 98.2 (d,
6-C), 143.2 (s, 3-C), 151.2 (d, 4-C), 198.0 (s, CvO), 205.3
(s, CvO), 207.2 (s, 7-C); MS m/z (rel. intensity) 192 (Mþ,
4), 178 (10), 177 (69), 159 (10), 150 (12), 149 (31), 137
(11), 135 (21), 134 (15), 107 (11), 91 (16), 43 (100).
HRMS Found: m/z 192.1095. Calcd for C12H16O2; Mþ,
192.1151.
solvent, the residual oil was subjected to medium-pressure
silica gel chromatography using 2.5% ether–hexane as an
eluent to give (Z )-2-(2,2,5-trimethyl-3,4-hexadienylidene)-
cyclopentanone (9: 50 mg, 6%), 2-isopropylidene-10,10-
dimethyl-3-oxatricyclo[7.1.0.04,8]deca-4(8)-ene (10: 42 mg,
5%), cis-3-isopropylidene-5,5-dimethylspiro[bicyclo[2.1.0]-
pentane-2,20-cyclopentanone (11: 91 mg, 11%), and its
trans-isomer (12: 140 mg, 17%).
Data for 6. Yield 21%; IR (neat) 1967 (CvCvC), 1712
(CvO), 1665 (CvO), 1626 (CvC) cm21
;
1H NMR
Data for 9. IR (neat) 2962, 2933, 2908, 2870, 1969
1
(CDCl3, 400 MHz) d 1.21 (6H, s, 5-Me£2), 1.71 (6H, d,
J¼2.9 Hz, CvCvCMe2), 2.31 (3H, s, MeCvO), 2.34 (3H,
s, MeCvO), 4.98 (1H, septet, J¼2.9 Hz, CvCvCH), 6.56
(1H, s, CHvC); 13C NMR (CDCl3, 100 MHz) d 20.3 (2C, q,
9-C), 25.9 (q, 1-C), 28.4 (2C, q, 5-Me), 33.0 (q, 1-C), 38.0
(s, 5-C), 96.9 (d, 6-C), 98.7 (s, 8-C), 143.0 (s, 3-C), 151.9 (d,
4-C), 198.1 (s, CvO), 200.1 (s, 7-C), 205.2 (s, CvO); MS
m/z (rel. intensity) 220 (Mþ, 5), 205 (18), 111 (10), 43 (100),
41 (13). HRMS Found: m/z 220.1432. Calcd for C14H20O2;
M, 220.1464.
(CvCvC), 1717, (CvO), 1624 (CvC) cm21; H NMR
(CDCl3, 90 MHz) d 1.27 (6H, s, 2-Me£2), 1.68 (6H, d,
J¼2.6 Hz, CvCvCMe2), 1.69–2.04 (2H, m, CH2), 2.32
(2H, t, J¼7.5 Hz, COCH2), 2.61 (2H, dt, J¼2.2, 9.2 Hz,
vCCH2), 5.38 (1H, septet, J¼2.6 Hz, CHvCvC), 5.99
(1H, t, J¼2.2 Hz, CHvC); 13C NMR (CDCl3, 22.5 MHz) d
20.5 (t), 20.8 (2C, q, 6-C), 28.3 (2C, q, 2-Me), 34.0 (t), 37.2
(s), 41.0 (t), 97.3 (s, 5-C), 98.8 (d, 3-C), 135.5 (s, sCv),
148.0 (d, 1-C), 199.2 (s, 4-C), 206.0 (s, CvO); MS m/z (rel.
intensity) 204 (Mþ, 25), 189 (100), 186 (22), 171 (48), 161
(35), 148 (31), 137 (27), 134 (67), 133 (45), 119 (27), 105
(27), 95 (45), 91 (31), 79 (23), 77 (24), 67 (32), 55 (33), 43
(20), 41 (55), 38 (23). HRMS Found: m/z 204.1506. Calcd
for C14H20O; M, 204.1515.
5.3. Photochemistry of 1–6
5.3.1. Photochemistry of 1. A solution of 1 (800 mg,
4.55 mmol) in hexane (400 cm3) was degassed with argon
and then irradiated for 6 h using a 100 W high-pressure
mercury lamp with a pyrex jacket. After evaporation of the
solvent, the photoproducts were separated by medium-
pressure silica gel chromatography using 2.5% ether–
hexane as an eluent to give (Z)-2-(2,2-dimethyl-3,4-
pentadienylidene)cyclopentanone (7: 64 mg, 8%) and
10,10-diemthyl-2-methylene-3-oxatricyclo[7.1.0.04,8]deca-
4(8)-ene (8: 201 mg, 25%).
Data for 10. IR (neat) 2953, 2943, 2916, 2855, 1703
1
(CvC), 1680 (CvC) cm21; H NMR (CDCl3, 90 MHz) d
0.76 (3H, s, 10-Me), 1.19 (3H, s 10-Me), 1.20 (1H, d,
J¼8.8 Hz, CH), 1.57 (1H, d, J¼8.8 Hz, CH), 1.70 (6H, s,
vCMe2), 1.70–1.96 (2H, m, CH2), 2.23–2.47 (4H, m,
CH2CH2); 13C NMR (CDCl3, 22.5 MHz) d 15.5 (q), 16.6
(q), 18.8 (q), 19.5 (t), 22.8 (d), 23.4 (d), 25.1 (s, 10-C), 26.6
(q), 30.4 (t), 31.8 (t), 104.8 (s, vC), 108.7 (s, vC), 141.0 (s,
O–Cv), 147.9 (s, O–Cv); MS m/z (rel. intensity) 204
(Mþ, 90), 203 (28), 189 (100), 161 (37), 148 (27), 134 (58),
133 (36), 119 (27), 105 (27), 91 (25), 55 (21), 41 (32).
HRMS Found: m/z 204.1492. Calcd for C14H20O; M,
204.1515.
Data for 7. IR (neat) 1953 (CvCvC), 1715, (CvO), 1623
1
(CvC) cm21; H NMR (CDCl3, 90 MHz) d 1.31 (6H, s,
5-Me£2), 1.71–2.05 (2H, m, CH2), 2.34 (2H, t, J¼7.1 Hz,
COCH2), 2.62 (2H, dt, J¼1.6, 7.1 Hz, vCCH2), 4.77 (2H,
d, J¼6.6 Hz, CvCvCH2), 5.71 (1H, t, J¼6.6 Hz,
CHvCvC), 5.99 (1H, t, J¼1.6 Hz, CHvC); 13C NMR
(CDCl3, 22.5 MHz) d 20.5 (t), 28.3 (2C, q, 2-Me), 34.0 (t),
35.9 (s, 2-C), 41.1 (t), 77.1 (t, 5-C), 99.4 (d, 3-C), 136.0 (s,
vC), 147.2 (d, 1-C), 206.2 (s), 206.4 (s); MS m/z (rel.
intensity) 176 (Mþ, 25), 175 (21), 161 (100), 119 (23), 105
(51), 91 (29), 55 (25), 41 (28), 38 (24). HRMS Found: m/z
176.1230. Calcd for C12H16O; M, 176.1202.
Data for 11. IR (neat) 1734 (CvO), 1640 (CvC) cm21; 1H
NMR (CDCl3, 90 MHz) d 0.97 (3H, s, 5-Me), 1.20 (3H, s,
5-Me), 1.45 (3H, s, vCMe), 1.49 (1H, d, J¼5.3 Hz, CH),
1.67 (3H, s, vCMe), 1.67–2.43 (7H, m, including CH as a
doublet of J¼5.3 Hz at 2.21 ppm); 13C NMR (CDCl3,
22.5 MHz) d 18.6 (q), 18.8 (q), 19.0 (q), 19.2 (t), 24.1 (q),
26.7 (s, 5-C), 31.8 (d, 1-C), 31.9 (t), 34.6 (d, 4-C), 38.4 (t),
56.5 (s, 2-C), 121.1 (s, vC), 133.7 (s, vC), 221.0 (s,
CvO); MS m/z (rel. intensity) 204 (Mþ, 11), 161 (47), 148
(45), 133 (100), 105 (21), 91 (22), 41 (24). HRMS Found:
m/z 204.1506. Calcd for C14H20O; M, 204.1515.
Data for 8. IR (neat) 1702 (CvC) cm21; 1H NMR (CDCl3,
90 MHz) d 0.86 (3H, s, 10-Me), 1.16 (3H, s, 10-Me), 1.29
(1H, d, J¼8.5 Hz), 1.66 (d, J¼8.5 Hz), 1.71–2.47 (6H, m,
CH2CH2CH2), 4.21 (1H, d, J¼0.9 Hz, vCH), 4.52 (1H, d,
J¼0.9 Hz, vCH); 13C NMR (CDCl3, 22.5 MHz) d 14.9 (q),
19.6 (t), 24.0 (d), 25.5 (s, 10-C), 26.7 (q), 27.1 (d), 30.2 (t),
31.7 (t), 88.9 (t, vCH2), 106.2 (s, vC), 146.8 (s, O–Cv),
154.0 (s, O–Cv); MS m/z (rel. intensity) 176 (Mþ, 78), 175
(42), 161 (100), 135 (30), 121 (20), 119 (21), 105 (31), 91
(26), 55 (24), 43 (26), 41 (20). HRMS Found: m/z 176.1198.
Calcd for C12H16O; M, 176.1202.
Data for 12. IR (neat) 1736 (CvO), 1628 (CvC) cm21; 1H
NMR (CDCl3, 90 MHz) d 0.91 (3H, s, 5-Me), 1.28 (3H, s,
5-Me), 1.45 (3H, s, vCMe), 1.60 (3H, s, vCMe), 1.68 (1H,
d, J¼5.4 Hz, CH), 1.92–2.55 (7H, m, including CH as a
doublet of J¼5.4 Hz at 1.99 ppm); 13C NMR (CDCl3,
22.5 MHz) d 17.9 (t), 18.2 (q), 18.6 (t), 19.4 (t), 24.9
(q), 28.8 (s, 5-C), 32.6 (d, 1-C), 36.2 (t), 36.5 (d, 4-C), 36.8
(t), 55.6 (s, 2-C), 123.8 (s, vC), 130.7 (s, vC), 217.2
(s, CvO); MS m/z (rel. intensity) 204 (Mþ, 10), 161 (50),
148 (41), 133 (100), 105 (23), 43 (57), 39 (24), 36 (29).
HRMS Found: m/z 204.1475. Calcd for C14H20O; M,
204.1515.
5.3.2. Photochemistry of 2. A solution of 2 (830 mg,
4.07 mmol) in hexane (400 cm3) was degassed with argon
and then irradiated for 6 h using a 100 W high-pressure
mercury lamp with a pyrex jacket. After evaporation of the

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T. Tsuno et al. / Tetrahedron 58 (2002) 7681–7689
5.3.3. Photochemistry of 3. A solution of 3 (760 mg,
4.00 mmol) in hexane (400 cm3) was irradiated for 1 h using
a 100 W high-pressure mercury lamp with a pyrex jacket
under an argon atmosphere. After evaporation of the
solvent, the residue was subjected to medium-pressure
silica gel chromatography using 2.5% ether–hexane as an
eluent to give (Z )-2-(2,2-dimethyl-3,4-pentadienylidene)-
cyclohexanone (13) in 51% (390 mg) yield: IR (neat) 1953
5.3.6. Photochemistry of 5. A solution of 5 (768 mg,
4.00 mmol) in hexane (400 cm3) was irradiated using a
100 W high pressure mercury lamp with a pyrex jacket
under an argon atmosphere at room temperature. The
reaction was monitored by GLC. Irradiation was stopped
(9 h), when 5 had disappeared by 65%. After evaporation of
the solvent, the residual oil was subjected to medium-
pressure silica gel chromatography using 10% ether–
hexane as an eluent to give 5-acetyl-4,7,7-trimethyl-2-
methylene-3-oxabicyclo[4.1.0]hepta-4-ene (16: 55 mg,
7%), 2,2-diacetyl-5,5-dimethyl-3-methylenebicyclo[2.1.0]-
pentane (17: 77 mg, 10%), and 1,4-diacetyl-3,3-dimethyl-5-
methylenecyclopenta-1-ene (18: 13 mg, 2%).
1
(CvCvC), 1696 (CvO), 1636 (CvC) cm21; H NMR
(CDCl3, 400 MHz) d 1.20 (6H, s, 2-Me£2), 1.70–1.81 (2H,
m, CH2), 1.88–1.94 (2H, m, CH2), 2.39 (2H, br t, J¼6.1 Hz,
vCCH2), 2.44 (2H, t, J¼6.6 Hz, COCH2), 4.74 (2H, d,
J¼6.6 Hz, CvCvCH2), 5.27 (1H, t, J¼6.6 Hz,
CHvCvC), 5.41 (1H, t, J¼1.3 Hz, CHvC); 13C NMR
(CDCl3, 100 MHz) d 27.1 (t), 27.4 (t), 29.2 (2C, q, 2-Me),
35.9 (s, 2-C), 39.2 (t), 44.8 (t), 77.0 (t, 5-C), 100.0 (d, 3-C),
139.0 (d, 1-C), 139.6 (s, vC), 206.6 (s, 4-C), 208.2 (s,
CvO); MS m/z (rel. intensity) 190 (Mþ, 10), 189 (25), 175
(100), 151 (35), 119 (20), 105 (31), 91 (28), 79 (21), 43 (23),
41 (31). HRMS Found: m/z 190.1344. Calcd for C13H18O;
M, 190.1358.
Data for 16. IR (neat) 1699 (CvO), 1680 (CvC), 1590
1
(CvC) cm21; H NMR (C6D6, 90 MHz) d 0.73 (3H, s,
7-Me), 0.89 (3H, s, 7-Me), 1.19 (1H, d, J¼8.8 Hz, 1-CH),
1.46 (1H, d, J¼8.8 Hz, 6-CH), 1.98 (3H, s, COMe), 2.26
(3H, s, 4-Me), 4.21 (1H, d, J¼0.9 Hz, vCH), 4.75 (1H, d,
J¼0.9 Hz); 13C NMR (CDCl3, 22.5 MHz) d 14.9 (q), 19.1
(q), 24.2 (d, 6-C), 25.1 (s, 7-C), 25.4 (d, 1-C), 26.4 (q), 29.7
(q), 92.5 (t, vCH2), 108.8 (s, 5-C), 151.1 (s), 157.6 (s),
198.7 (s, CO); MS m/z (rel. intensity) 192 (Mþ, 43), 177
(29), 149 (14), 135 (16), 91 (12), 43 (100). HRMS Found:
m/z 192.1120. Calcd for C12H16O2; M, 192.1151.
5.3.4. 11,11-Dimethyl-2-methylene-3-oxatricyclo-
[8.1.0.04.9]undeca-4(9)-ene (14).
A
hexane solution
(170 cm3) of 3 (324 mg) was irradiated for 18 h using a
100 W high-pressure mercury lamp with a pyrex jacket
under an argon atmosphere. After evaporation of the
solvent, the residue was chromatographed on neutral
activated aluminum oxide to give 13 and 14 in 8%
(29 mg) and 6% (20 mg) yields, respectively.
Data for 17. IR (neat) 1720 (CvO), 1699 (CvO), 1672
1
(CvC) cm21; H NMR (C6D6, 90 MHz) d 0.68 (3H, s,
5-Me), 0.94 (3H, s, 5-Me), 1.82 (1H, d, J¼4.8 Hz, 4-CH),
1.98 (3H, s, COMe), 2.15 (1H, d, J¼4.8 Hz, 1-CH), 2.29
(3H, s, COMe), 4.78 (1H, s, vCH), 5.17 (1H, d, J¼0.9 Hz);
13C NMR (CDCl3, 22.5 MHz) d 17.9 (q), 24.1 (q), 25.4 (q),
27.2 (q), 27.6 (s, 5-C), 31.7 (d, 4-C), 35.6 (d, 1-C), 73.6 (s,
2-C), 108.3 (t, vCH2), 143.7 (s, 3-C), 202.2 (s, CO), 206.3
(s, CO); MS m/z (rel. intensity) 192 (Mþ, 0.1), 150 (12), 149
(15), 135 (15), 108 (20), 107 (17), 93 (10), 91 (13), 43 (100).
HRMS Found: m/z 192.1120. Calcd for C12H16O2; M,
192.1151.
Data for 14. IR (CHCl3) 1714 (CvC) cm21 1H NMR
;
(CDCl3, 400 MHz) d 0.89 (3H, s, 11-Me), 1.16 (3H, s,
11-Me), 1.60–2.42 (8H, m, CH2CH2CH2 and 2£CH), 4.10
(1H, s, vCH), 4.42 (1H, s, vCH); 13C NMR (CDCl3,
100 MHz) d 15.2 (q), 23.3 (t), 23.4 (t), 24.9 (s), 26.7 (t), 27.1
(d), 27.3 (d), 28.4 (q), 29.1 (t), 88.4 (t, vCH2), 104.2 (s),
143.0 (s), 153.6 (s); MS m/z (rel. intensity) 190 (Mþ,
51),189 (29), 176 (15), 175 (100), 162 (18), 148 (17), 133
(6), 119 (6), 105 (9). HRMS: m/z 190.1332. Calcd for
C13H18O; M, 190.1358.
Data for 18. IR (neat) 1720 (CvO), 1699 (CvO), 1672
1
(CvC) cm21; H NMR (CDCl3, 90 MHz) d 1.13 (3H, s,
3-Me), 1.28 (3H, s, 3-Me), 2.11 (3H, s, COMe), 2.39 (3H, s,
COMe), 3.50 (1H, dd, J¼1.7, 1.8 Hz, 4-CH), 5.07 (1H, dd,
J¼1.3, 1.7 Hz), 5.07 (1H, d, J¼1.8 Hz), 6.71 (1H, d,
J¼1.3 Hz); 13C NMR (CDCl3, 22.5 MHz) d 22.8 (q), 28.3
(q), 29.7 (q), 30.7 (q), 46.0 (s, 3-C), 68.4 (d, 4-C), 112.6 (t,
vCH2), 139.4 (s, vC), 146.1 (s, vC), 157.5 (d, vCH),
196.2 (s, CO), 207.8 (s, CO); MS m/z (rel. intensity) 192
(Mþ, 54), 150 (44), 149 (73), 135 (70), 119 (10), 109 (11),
108 (100), 107 (66), 93 (33), 91 (29), 79 (15), 77 (12), 65
(14). HRMS Found: m/z 192.1088. Calcd for C12H16O2; M,
192.1151.
5.3.5. Photochemistry of 4. A solution of 4 (870 mg,
3.99 mmol) in hexane (400 cm3) was irradiated for 1 h using
a high-pressure mercury lamp with a pyrex jacket under
argon atmosphere. After evaporation of the solvent, the
residue was subjected to medium-pressure silica gel
chromatography using 2.5% ether–hexane as an eluent to
give
hexanone (15) in 51% (440 mg) yield. IR (neat) 1950
(Z )-2-(2,2,5-trimethyl-3,4-hexadienylidene)cyclo-
1
(CvCvC), 1689 (CvO), 1638 (CvC) cm21; H NMR
(CDCl3, 90 MHz) d 1.14 (6H, s, 2-Me£2), 1.69 (6H, s,
CvCvCMe2), 1.75–2.10 (4H, m), 2.30–2.55 (4H, m),
5.03 (1H, septet, J¼2.6 Hz, CHvCvC), 5.39 (1H, t,
J¼2.6 Hz, CHvC); 13C NMR (CDCl3, 22.5 MHz) d
20.7 (2C, q, 6-C), 27.2 (t), 27.5 (t), 29.2 (2C, q, 2-Me),
37.0 (s, 2-C), 39.4 (t), 44.9 (t), 97.3 (s, 5-C), 99.0 (d, 3-C),
139.4 (2C, sd, 1-C and vC,), 199.4 (s, 4-C), 207.9 (s,
CvO); MS m/z (rel. intensity) 218 (Mþ, 12), 203 (100),
185 (55), 175 (20), 151 (34), 148 (63), 133 (29), 105 (25),
91 (25), 81 (20), 67 (24), 55 (30), 43 (31), 41 (50).
HRMS Found: m/z 218.1651. Calcd for C15H22O; M,
218.1671.
5.3.7. Photochemistry of 6. A solution of 6 (880 mg,
4.00 mmol) in hexane (400 cm3) was irradiated using a 100-
W high-pressure mercury lamp with a pyrex jacket under an
argon atmosphere at room temperature. The reaction was
monitored by GLC. Irradiation was stopped for 9 h, when 6
had disappeared by 5%. After evaporation of the solvent, the
residual oil was subjected to medium-pressure silica gel
chromatography using 10% ether–hexane as an eluent
to give 2,2-diacetyl-3-isopropylidene-5,5-dimethylbicyclo-
[2.1.0]pentane (19) in 22% (193 mg): IR (neat) 1719

T. Tsuno et al. / Tetrahedron 58 (2002) 7681–7689
7689
(CvO), 1691 (CvO) cm21; 1H NMR (CDCl3, 400 MHz) d
1.05 (3H, s, 5-Me), 1.06 (3H, s, 5-Me), 1.62 (3H, s, vCMe),
1.66 (3H, s, vCMe), 1.97 (1H, d, J¼5.1 Hz, 4-CH), 2.11
(3H, s, COMe), 2.29 (3H, s, COMe), 2.34 (1H, d, J¼5.1 Hz,
1-CH); 13C NMR (CDCl3, 22.5 MHz) d 17.2 (q), 19.3 (q),
19.5 (q), 24.2 (q), 25.1 (q), 26.8 (s, 5-C), 27.4 (q), 29.7 (d,
1-C), 35.4 (d, 4-C), 71.9 (s, 2-C), 126.5 (s), 128.1 (s), 205.1
(s, CO), 207.1 (s, CO); MS m/z (rel. intensity) 220 (Mþ, 1),
177 (43), 135 (69), 121 (14), 119 (21), 43 (100). HRMS
Found: m/z 220.1408. Calcd for C14H20O2; M, 220.1464.
5. Kudrawcew, M.; Feri, B.; Wolf, H. R.; Jeger, O. Heterocycles
1982, 17, 139–150.
6. Zimmerman, H. E.; Armesto, D. Chem. Rev. 1996, 96,
3065–3112. Zimmerman, H. E. In CRC Handbook of Organic
Photochemistry and Photobiology. Horspool, W., Song, P.-S.,
Eds.; CRC: New York, 1995; pp 184–193. Zimmerman, H. E.
Org. Photochem. 1991, 11, 1–36. Zimmerman, H. E. Top.
Curr. Chem. 1982, 100, 45–73. Zimmerman, H. E. Acc. Chem.
Res. 1982, 15, 312–317.
7. Zimmerman, H. E.; Factor, R. E. Tetrahedron 1981, 37 (Suppl.
¨
1), 125–141. Baeckstrom, P. Tetrahedron 1978, 34,
5.4. Measurements of quantum yields
¨
3331–3335. Baeckstrom, P. J. Chem. Soc., Chem. Commun.
1976, 476–477. Bullivant, M. J.; Pattenden, G. J. Chem. Soc.,
Perkin Trans. 1 1976, 256–258.
The quantum yields of the isomerization of 1–6 to the
photoproducts were measured by GLC analyses, and the
photolyses were carried out by a merry-go-round method. A
450 W high-pressure mercury lamp through a combination
of a K2CrO4 solution and a pyrex filter was used as a 313 nm
irradiation source. Argon was bubbled into a solution
(10 cm3) of 1–7, 9, 13, and 15 (0.01 mol dm23) in a pyrex
tube. The solution was irradiated at room temperature. The
light intensity was determined by stilbene actinometry.11
These quantum yields are described in Tables 2 and 3.
8. Zimmerman, H. E.; Armesto, D.; Amezua, M. G.; Gannett,
T. P.; Johnson, R. P. J. Am. Chem. Soc. 1979, 101, 6376–6383.
Zimmerman, H. E.; Cassel, J. M. J. Org. Chem. 1989, 54,
3800–3816.
9. Kueh, J. S. H.; Mellor, M.; Pattenden, G. J. Chem. Soc., Perkin
Trans. 1 1981, 1052–1056. Barker, A. J.; Kueh, J. S. H.;
Mellor, M.; Otieno, D. A.; Pattenden, G. Tetrahedron Lett.
1979, 1881–1884.
10. Schneider, R. A.; Meinwald, J. J. Am. Chem. Soc. 1967, 89,
2023–2032. Meinwlad, J.; Kobzina, J. W. J. Am. Chem. Soc.
1969, 91, 5177–5178.
5.5. MO Calculation
11. (a) Tsuno, T.; Sugiyama, K. Recent Research Developments in
Organic Chemistry, Pandalai, S. G., Ed.; Transworld Research
Network: Trivandrum, 1999; Vol. 3, pp 435–453. (b) Tsuno,
T.; Sugiyama, K. Bull. Chem. Soc. Jpn 1999, 72, 519–531.
(c) Tsuno, T.; Hoshino, H.; Sugiyama, K. Tetrahedron Lett.
1997, 38, 1581–1584. (d) Tsuno, T.; Sugiyama, K. Bull.
Chem. Soc. Jpn 1995, 68, 3175–3188. (e) Sugiyama, K.;
Tsuno, T. Chem. Express 1992, 7, 929–932. (f) Tsuno, T.;
Sugiyama, K. Chem. Lett. 1991, 503–507. (g) Tsuno, T.;
Sugiyama, K. Trends in Heterocyclic Chemistry,
Ramachandran, U., Ed.; Research Trends: Trivandrum,
2001; Vol. 7, pp 91–106.
MO calculation was performed using the PM3 method of
Hyper Chem from Auto Disk, Inc., or Mac Spartan Plus of
Wavefunction, Inc.
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