A simple synthesis of bis-annulated bicyclo[2.2.2]octenones containing a β,γ-enone chromophore and photochemical reactions: A new entry into angular tetraquinane and other polycyclic systems

Article abstract of DOI:10.1016/j.tet.2004.08.024

Synthesis of endotetracyclo[5.5.2.0.^2,60^8,12] tetradeca-3(4),8(12)-dien-13-one from 5-indanol and photoreactions in singlet and triplet excited state leading to complex polycyclic systems is reported. Crystal structure of 14-spiroepoxyendotetracyclo[5.5.2.0.^2,60 ^8,12] tetradeca-3(4),8(12)-dien-13-one is also reported. Graphical Abstract

Full text of DOI:10.1016/j.tet.2004.08.024

Tetrahedron 60 (2004) 9925–9930
A simple synthesis of bis-annulated bicyclo[2.2.2]octenones
containing a b,g-enone chromophore and photochemical
reactions: a new entry into angular tetraquinane and other
polycyclic systems
a
b
Vishwakarma Singh,a, Pramod K. Sahu and Shaikh M. Mobin
*
aDepartment of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
bNational Single Crystal X-ray Diffraction Facility, Indian Institute of Technology Bombay, Mumbai 400076, India
Received 12 May 2004; revised 22 July 2004; accepted 13 August 2004
Available online 11 September 2004
Abstract—Synthesis of endotetracyclo[5.5.2.0.2,608,12]tetradeca-3(4),8(12)-dien-13-one from 5-indanol and photoreactions in singlet and
triplet excited state leading to complex polycyclic systems is reported. Crystal structure of 14-spiroepoxyendotetracyclo[5.5.2.0.2,608,12
tetradeca-3(4),8(12)-dien-13-one is also reported.
q 2004 Elsevier Ltd. All rights reserved.
]
1. Introduction
and also report photochemical reactions of 1 in triplet and
singlet excited state that provides a new stereoselective
entry to 2, 3 and other carbocyclic systems (Fig. 1).
Bridged carbocyclic systems containing a b,g-enone
chromophore have proved to be versatile precursors for
the synthesis of a variety of carbocyclic arrays because of
their unique reactions in both the ground and excited
states.1–3 The reactions in excited states permit a smooth
and stereoselective transformation of bridged structure into
ring fused system present in a large number of naturally
occurring compounds.2 However, while there are some
methods for the synthesis of simple bicyclo[2.2.2]octe-
nones4 and monoannulated homologue,5 there are no
methods for bis-annulated bicyclo[2.2.2]octenes of type 1
having a b,g-enone chromophore. Recently, the reactive
species generated from aromatics such as cyclohexadienone
ketals, o-imido quinones have received greater attention for
creation of complex molecular structures.6,7 In view of our
interest5 in the chemistry of cyclohexa-2,4-dienones and the
continuing interest in the synthesis of angular tetraqui-
nanes8,9 we thought to devise a method for the synthesis of
bis-annulated bicyclo[2.2.2]octenones of type 1 containing
a b,g-enone group and explore its photoreactions. We wish
to describe an efficient synthesis of tetracyclic compounds
of type 1 from a simple aromatic precursor 5 via
cycloaddition of the annulated cyclohexa-2,4-dienone 4,
2. Results and discussion
The tetracyclic dienone 1 was efficiently synthesized from
indanol 6 as follows. The hydroxymethyl indanol 510 was
prepared by controlled hydroxymethylation of commer-
cially available indanol 6 (Scheme 1). Thus, the treatment of
6 with aq. HCHO and NaOH at ambient temperature gave a
mixture of mono- and bis-hydroxymethylated products from
which hydroxymethyl indanol 5 was obtained in moderate
yield after chromatography. Oxidation of 5 in the presence
of a freshly cracked cyclopentadiene with aq. sodium
metaperiodate11 following a procedure developed in our
laboratory,5 gave the keto-epoxy adduct 8 in excellent yield
(83%) as a result of in situ generation of 4 and subsequent
interception with cyclopentadiene (Scheme 1). The gross
structure of the adduct was deduced from the following
spectroscopic data. Thus, the 1H NMR (400 MHz) spectrum
of the adduct exhibited characteristic signals at d 5.67 (m,
1H), 5.39 (m, 1H) for the olefinic protons of the five-
membered ring. Further, characteristic AB pattern for
protons of the oxirane methylene group was observed at d
3.10 (part of an AB system, JABZ6.1 Hz, 1H), 2.83 (part of
an AB system, JABZ6.1 Hz, 1H). In addition, signals were
observed at d 3.42–3.39 (superimposed m, 2H), 3.08–3.00
(m, 1H), 2.62–2.49 (m, 3H), 2.44–2.32 (m, 2H), 2.23–2.21
Keywords: Cycloaddition; Cyclohexa-2,4-dienone; Oxa-di-p-methane
rearrangement; 1,3-Acyl shift; Photoreaction.
* Corresponding author. Tel.: C91-2225767168; fax: C91-2225723480;
e-mail: vks@chem.iitb.ac.in
0040–4020/$ - see front matter q 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2004.08.024

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V. Singh et al. / Tetrahedron 60 (2004) 9925–9930
Figure 1.
(m, 1H), 2.02–1.87 (m, 3H) for other methine and
methylene protons. 13C NMR spectrum displayed charac-
teristic signals at d 205.02, and 140.75, 136.64, 133.00,
129.21 for carbonyl carbon and olefinic carbons respect-
ively. Signals due to other carbons were shown at d 58.95,
53.58, 52.57, 50.44, 44.60, 38.34, 36.89, 35.42, 34.17,
23.69. However, the stereochemical orientation of the
oxirane ring was not easily discernible from the spectro-
scopic data alone and it was difficult to distinguish between
8 and the possible diastereoisomer 9. Hence, X-ray crystal
structure determination was undertaken which confirmed
the structure 8 for the adduct (Fig. 2).
1 (Scheme 1). It may be worth noting that the tetracyclic
compounds of type 1 are not readily accessible otherwise.
After having an efficient access to the tetracyclic chromo-
phoric system 1, we first explored its photochemical
reaction in excited singlet (1S) state. In general, the rigid
b,g-enones undergo two unique reactions i.e. a 1,2-acyl shift
or oxa-di-p-methane rearrangement on triplet sensitized
(T1, p–p*) irradiation and a 1,3-acyl shift upon direct
irradiation either via singlet excited state (S1) and/or higher
triplet (T2, n–p*) state.1–3 The unusual reactivity is a
consequence of the electronic interaction between the
chromophores that modulates the structure and properties
of the excited states. However, the selectivity in the
photoreaction also depends on the structure of the
chromophoric systems and functional groups in a subtle
fashion. Keeping the above in mind, a solution of 1 in dry
benzene was irradiated with a mercury vapor lamp (125 W,
APP) in a Pyrex immersion well under nitrogen. Chroma-
tography of the photolysate gave the tetracyclic compound 3
(Scheme 2) containing a cyclobutanone ring in a good yield
(40%) as a result of 1,3-acyl shift. The structure of the
photoproduct was clearly revealed from the spectroscopic
data. In order to examine the photoreaction of 1 in triplet
excited state, a solution of 1 in dry acetone (both as a solvent
and sensitizer) was irradiated with a mercury vapor lamp
The adduct 8 was then converted into the chromophoric
system 1. Thus, the treatment of 8 with zinc in aqueous
methanol containing NH4Cl at ambient temperature gave
the b-hydroxy ketone 10 (as a mixture of syn–anti isomers)
also in excellent yield (92%). Oxidation of 10 with Jones
reagent followed by decarboxylation of the resulting b-
ketoacid readily furnished the desired chromophoric system
Scheme 1. Reagents/conditions: (i) NaOH, HCHO, 5 (30%), 7 (30%);
(ii) aq. NaIO4, CH3CN, cyclopentadiene, 0–5 8C, 83%; (iii) Zn, NH4Cl, aq.
MeOH, rt, 92%; (iv) Jones reagent, acetone; (v) aq. THF, 6, 55% (for iv
and v).
Figure 2. X-ray crystal structure of compound 8.

V. Singh et al. / Tetrahedron 60 (2004) 9925–9930
9927
Scheme 2.
(125 W, APP) in a Pyrex immersion well (lO290 nm)
under nitrogen for 1 h. Chromatography of the photolysate
gave the tetracyclic dienone 3, the caged ketone 11 and the
polyquinane 2 in 23, 15 and 20% yields respectively, as a
result of 1,3-acyl shift, intramolecular p2sCp2s cycloaddi-
tion and oxa-di-p-methane rearrangement. In order to
improve the efficiency of the oxa-di-p-methane reaction,
we also irradiated a solution of 1 in acetone at 254 nm
(16 W mercury vapor lamp APP) in a quartz immersion well
for 3 h. Under this condition, the oxa-di-p-methane product
2 was obtained in better yield (35%), the formation of 1,3-
acyl shift product 3 remained unchanged and the caged
product 11 was formed to a greater extent (Scheme 2).
benzene furnished the tetraquinane 12 in good yield (65%)
(Scheme 3). The presence of an absorption band at
1737 cmK1 in IR spectrum and a signal at d 223.15 in the
13C spectrum of 12, characteristic of a CO group in five-
membered ring, in addition to other spectral data clearly
suggested its structure.
In summary, transformation of a readily available aromatic
precursor to a new complex tetracylic system 1 endowed
with a b,g-enone chromophore and its photoreaction upon
singlet and triplet excited state leading to novel carbocyclic
systems is described. An unusual effect of structure on the
photoreactivity in the triplet excited state is also presented.
The formation of the 1,3-acyl shift product 3 and, especially
the caged product 11 during the sensitized irradiation of 1
was rather surprising since other bicyclo[2.2.2]octenones
without the substituents at b,g-olefinic carbons undergo
highly selective photoreaction.2,3,5 It appears that the
unusual behavior of the tetracyclic compound 1 upon
sensitized irradiation is due to the presence of the strained
five-membered ring across the b,g-olefinic bond which
controls the structure and properties (electronic and steric
effects) of both the ground and the excited state so as to
populate T2 and T1 indiscriminately and also sensitize the p-
bonds for intramolecular photocycloaddition.
3. Experimental
3.1. General
IR spectra were recorded on Nicolet Impact 400 FT-IR
Instrument. UV spectra were recorded on Shimadzu UV 160
1
or Shimadzu U 260 instrument. H NMR and 13C NMR
were recorded on Bruker Avance-400 NMR spectrometer,
Varian NMR and Varian VXR 300 instruments. Micro-
analyses were done on a CEST 1106 instrument and HRMS
was done on Q-Tof micro (YA-105) and Brucker Daltonics
APEX3 Tesla Mass Spectrometer. Melting points were
determined on a Veego apparatus of Buchi type and are
uncorrected. All the organic extracts were dried over
anhydrous sodium sulphate. Reactions were monitored
with thin layer chromatography silica gel and spots were
visualized with iodine vapor. Column chromatography was
performed using Acme/SRL silica gel (60–120 or 100–200
mesh). The elution was done with petroleum ether (60–
80 8C) and ethyl acetate mixtures. The fractions eluted from
column were concentrated at reduced pressure on a Buchi-
RE 111 rotary evaporator.
The oxa-di-p-methane rearrangement in 1, although it
occurred with moderate efficiency, provided a stereoselec-
tive route to angular polyquinanes which are present in
many natural products.8,9 In order to convert the pentacyclic
compound 2 into tetraquinane, selective cleavage of the
peripheral cyclopropane bond was required. Though several
methods are available,12 radical induced reductive clea-
vage13 was attempted. Thus, treatment of the pentacyclic
compound 2 with tributyltin hydride-AIBN in refluxing
3.1.1. 6-Hydroxymethyl-5-indanol (5) and 2,6-dihydrox-
ymethylindanol (7). To a solution of indanol 6 (3.0 g,
22.4 mmol) in water (120 mL), NaOH (0.76 g, 19 mmol)
and formaldehyde (2 mL, excess) were added at ambient
temperature and the reaction mixture was stirred for 3 h.
Then the reaction mixture was neutralized with NH4Cl, at
0 8C and extracted with ethyl acetate (4!50 mL). The
Scheme 3.

9928
V. Singh et al. / Tetrahedron 60 (2004) 9925–9930
combined organic extract was washed with brine (1!
20 mL) and dried over anhydrous sodium sulphate. The
solvent was removed under vaccum and the residue was
flash chromatographed. Elution with petroleum ether–ethyl
acetate (95:5) first gave the unreacted starting material.
Further elution with petroleum ether–ethyl acetate (90:10)
furnished the desired compound 5 (1.2 g, 30%) as a
colorless solid. Elution with petroleum ether–ethyl acetate
(70:30) gave the bis-hydroxymethylated product 7 (1.4 g,
30%) as a colorless crystalline solid.
0.35!0.22 mm3, reflections collected/uniqueZ1873/1873
[R(int)Z0.0000], final R indices [IO2sigma(I)]: R1Z
0.0383, wR2Z0.0866, R indices (all data): R1Z0.0579,
wR2Z0.0979. CCDC No. 245375. See: http//www.ccdc.
cam.ac.uk/conts/retrieving.html (e-mail: deposit@ccdc.
cam.ac.uk).
3.1.3. 14-Hydroxymethylendotetracyclo[5.5.2.02,6.08,12]-
tetradeca-3,8(12)-dien-13-one (10). To a solution of the
adduct 8 (3.0 g, 13.2 mmol) in methanol–water (6:1,
105 mL) was added zinc (activated 18 g, excess) and
NH4Cl (3.3 g, 59 mmol). The reaction mixture was stirred
at ambient temperature (w30 8C) for 8 h (TLC). It was
filtered on a celite bed and washed with ethyl acetate. The
filtrate was concentrated under reduced pressure and diluted
with water and extracted with ethyl acetate (4!40 mL).
The combined organic layer was washed with brine and
dried. The solvent was removed under reduced pressure and
the residue was chromatographed. Elution with petroleum
ether–ethyl acetate (88:12) gave the alcohol 10 (syn–anti
mixture) as a colorless liquid (2.8 g, 92%). IR nmax: 3446,
Data for 5. Mp 104–106 8C. IR nmax: 3434, 1591 cmK1. 1H
NMR (300 MHz, CDCl3): d 7.04 (s, 1H, phenolic-OH), 6.88
(s, 1H, aromatic proton), 6.76 (s, 1H, aromatic proton), 4.78
(d, JZ3 Hz, 2H, Ar-CH2-OH), 2.88–2.77 (m, 4H), 2.26 (br
m, 1H, CH2OH), 2.09–2.00 (m, 2H). 13C NMR (75 MHz,
CDCl3): d 154.59, 145.93, 135.55, 123.44, 122.54, 112.44,
64.66, 32.91, 31.90, 25.76. Analysis: Found C, 72.99; H,
7.71; requires C, 73.17; H, 7.31 for C10H12O2.
Data for 7. Mp 108–110 8C. IR nmax: 3405, 3318, 1610 cmK1
.
1H NMR (300 MHz, CDCl3): d 8.08 (s, 1H, phenolic OH),
6.92 (s, 1H), 4.84 (d, JZ3 Hz, 2H, CH2OH); 4.75 (d, JZ
3 Hz, 2H, CH2OH), 2.84–2.79 (m, 4H), 2.64 (br m, 1H,
OH), 2.52 (br m, 1H, OH), 2.08–2.03 (m, 2H). 13C NMR
(75 MHz, CDCl3): d 153.4, 142.8, 135.3, 124.4, 123.2,
121.5, 63.6, 60.9, 32.1, 31.0, 25.3. HRMS: 217.0848 (MCC
Na) C11H14O3Na requires, 217.0841.
1
1714 cmK1. H NMR (400 MHz, CDCl3): d 5.63–5.59 (m,
1H), 5.38–5.32 (m, 1H), 3.90–3.80 (m, 1H), 3.70–3.64 (m,
1H), 3.55 (d, JZ7.8 Hz, 1H), 3.30–3.14 (merged m, 3H),
2.97, 2.87 (m, total 1H), 2.80–2.70 (m, 1H), 2.60–2.20
(cluster of m, 6H), 2.0–1.82 (m, 2H). 13C NMR (100 MHz,
CDCl3): d 215.77, 143.85, 135.74, 134.62, 129.53, 62.82,
54.46, 50.85, 50.36, 40.46, 40.43, 38.35, 35.48, 35.09,
33.78, 23.50 (signals due to one isomer). HRMS: 253.1205
(MCCNa), C15H18O2 requires 253.1199. This was sub-
jected to oxidation and decarboxylation as described below.
3.1.2. 14-Spiroepoxyendotetracyclo[5.5.2.0.2,608,12]tetra-
deca-3(4),8(12)-dien-13-one (8). To a solution of com-
pound 5 (3.0 g, 18.3 mmol) in acetonitrile (90 mL) was
added freshly cracked cyclopentadiene (8 mL, excess) at 0–
5 8C. To this was added a solution of sodium metaperiodate
(7.7 g, 36 mmol) dropwise. After stirring for 3 h at 0–5 8C,
the reaction mixture was brought to ambient temperature
and stirred overnight. The organic layer was separated and
the aqueous layer was saturated with sodium chloride and
extracted with ethyl acetate (3!40 mL). The combined
organic layer was washed with brine and dried over
anhydrous sodium sulfate. The solvent was removed under
reduced pressure and the residue was subjected to flash
chromatography on silica gel. Elution with petroleum ether
gave the unreacted cyclopentadiene dimer. Further elution
with petroleum ether–ethyl acetate (98:2) gave the desired
adduct 8 (3.43 g, 83%) as a solid which was recrystallized
with petroleum ether–ethylacetate. Mp 103–104 8C. IR
(film) nmax: 1734 cmK1. UV (MeOH) lmax: 215 (3Z3.67!
103 L molK1 cmK1), 312 (3Z3.31!102 L molK1 cmK1) nm.
1H NMR (400 MHz, CDCl3): d 5.67 (m, 1H), 5.39 (m, 1H),
3.1.4. endo-Tetracyclo[5.5.2.02,6.08,12]tetradeca-3,8(12)-
dien-13-one (1). A solution of the b-keto-alcohol 10
(2.0 g, 8.7 mmol) in acetone (60 mL) was oxidized with
freshly prepared Jones’ reagent at 0 8C. After completion of
reaction (TLC), isopropanol was added to destroy excess
oxidant. Acetone was removed in vacuum at ambient
temperature and the residue was diluted with water (10 mL)
and extracted with dichloromethane (3!25 mL). Combined
organic layer was washed with brine and dried over
anhydrous sodium sulfate. The solvent was removed and
the resulting b-keto-acid was dissolved in THF–water
mixture (1:1, 30 mL) and refluxed for 10 h. It was brought
to ambient temperature, and the organic layer was
separated. The aqueous layer was saturated with sodium
chloride and extracted with ether (3!30 mL). The com-
bined organic layer was washed with saturated sodium
bicarbonate, brine and dried over anhydrous sodium sulfate.
The solvent was removed under reduced pressure and the
residue was chromatographed on silica gel. Elution with
petroleum ether–ethylacetate (98:2) gave the titled com-
pound 1 (0.85 g, 55%) as a colorless solid. Mp 70–71 8C. IR
(film) nmax: 1723 cmK1. UV (MeOH) lmax: 218 (3Z9.02!
102 L molK1 cmK1), 297 (3Z1.6!102 L molK1 cmK1) nm.
1H NMR (400 MHz, CDCl3): d 5.62–5.57 (m, 1H), 5.38–
5.34 (m, 1H), 3.28–3.21 (m, 1H), 3.20 (d, JZ2.6 Hz, 1H),
2.94 (dd, JZ5.61, 2.81 Hz, 1H), 2.76–2.66 (complex m,
1H), 2.56–2.45 (overlapped m, 2H), 2.42–2.25 (m, 2H),
3.42–3.39 (m, 2H), 3.10 (part of an AB system, JAB
Z
6.1 Hz, 1H), 3.08–3.00 (m, 1H), 2.83 (part of an AB system,
JABZ6.1 Hz, 1H), 2.62–2.49 (m, 3H), 2.44–2.32 (m, 2H),
2.23–2.21 (m, 1H), 2.02–1.87 (m, 3H). 13C NMR
(100 MHz, CDCl3): d 205.02, 140.75, 136.64, 133.00,
129.21, 58.95, 53.58, 52.57, 50.44, 44.60, 38.34, 36.89,
35.42, 34.17, 23.69. HRMS: 229.1231 [MCCH], C15H16O2
requires 229.1223.
Crystal data. C15H16O2, MZ228.28, orthorhombic, P 21 21
2.24–2.14 (m, 1H), 2.08 (d of part of an AB system, JAB
18.2, 2.4 Hz, 1H), 2.02 (d of part of an AB system, JAB
Z
Z
˚
˚
˚
21 ZZ4, lZ0.70930 A, aZ8.000(2) A, bZ11.2730(12) A,
3
cZ13.0490(19) A, VZ1176.8(4) A , TZ293(2) K, DcZ
1.288 mg/m3, mZ0.084 mmK1, F(000)Z488, sizeZ0.40!
18.2, 3.2 Hz, 1H), 1.97–1.84 (m, 3H). 13C NMR (100 MHz,
˚
˚
CDCl3): d 212.66, 143.19, 135.67, 132.21, 129.84, 54.19,

V. Singh et al. / Tetrahedron 60 (2004) 9925–9930
9929
49.44, 41.08, 40.44, 38.47, 37.98, 35.04, 33.77, 23.66.
HRMS: 223.1096 [MCCNa], C14H16ONa requires
223.1099.
column of silica gel. The column was eluted with petroleum
ether to remove the tin impurity. Further elution with
petroleum ether–ethyl acetate (98:2) furnished the angular
tetraquinane 12 (59 mg, 73%) as a colorless liquid. IR (film)
nmax: 1737 cmK1. 1H NMR (400 MHz, CDCl3): d 5.72–5.54
(m, 2H), 3.34–3.21 (br m, 1H), 2.71–2.59 (complex m, 1H),
2.52–2.44 (dd, JZ18.6, 7.6 Hz, 1H), 2.42–2.34 (m, 1H),
2.33–1.98 (m, 4H), 1.92–1.79 (m, 2H), 1.76–1.55 (m, 5H),
1.52–1.40 (m, 1H). 13C NMR (100 MHz, CDCl3): d 223.15,
135.29, 128.21, 60.39, 58.36, 53.33, 51.26, 49.72, 45.87,
44.69, 40.10, 39.78, 29.96, 26.86. HRMS: 203.1438 (MCC
H) C14H18OCH requires, 203.1436.
3.1.5. Tetracyclo[9.3.0.01,4.05,9]tetradeca-7,10-dien-2-
one (3). A solution of the tetracyclic compound 1 (70 mg,
0.35 mmol) in dry benzene (100 mL) was irradiated with a
mercury vapor lamp (125 W, APP) in a Pyrex immersion
well for about 45 min. Removal of solvent followed by the
chromatography of the residue gave the 1,3-acyl shift
product 3 (31 mg, 40%) as colorless liquid. IR (film) nmax
:
1770 cmK1. 1H NMR (300 MHz, CDCl3CCCl4): d 5.87 (br
m, 1H), 5.64 (br m, 1H), 5.18 (s, 1H), 3.14 (br s, 1H), 3.10–
2.95 (dd, JZ9.1, 9.1 Hz, 1H), 2.76–2.70 (m, 1H), 2.69–2.59
(t, JZ8.3 Hz, 1H), 2.58–2.45 (dd, JZ18, 8.5 Hz, 1H), 2.44–
2.13 (complex m, 4H), 2.02–1.82 (m, 2H), 1.79–1.58 (m,
1H), 1.58–1.49 (m, 1H). 13C NMR (75 MHz, CDCl3C
CCl4): d 208.10, 136.09, 133.88, 130.30, 117.63, 68.96,
48.46, 40.98, 39.03, 36.25, 33.33, 30.05, 29.46, 21.75.
HRMS: 223.1088 [MCCNa], C14H16ONa requires
223.1093.
Acknowledgements
We are grateful to BRNS Mumbai for continued financial
support. Thanks are also due to RSIC, IIT Bombay for NMR
spectra.
3.1.6. Pentacyclo[6.6.0.01,11.02,11.03,7]tetradec-4-en-10-
one (2) and caged ketone (11). A solution of the compound
1 (0.3 g, 1.5 mmol) in acetone (400 mL) was irradiated with
References and notes
a medium pressure mercury vapor lamp (16 W, lmax
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1. (a) Horspool, W. M. Photochemistry Royal Society of
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(b) Zimmerman, H. E.; Armesto, D. 1996, 96, 3065–3112.
(c) Singh, V. Organic Photochemistry and Photobiology;
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254 nm) in a quartz immersion well for 3 h under nitrogen.
The solvent was removed and the residue was chromato-
graphed. Elution with petroleum ether–ethyl acetate (98:2)
first gave the 1,3-acyl shift product 3 (60 mg, 20%) followed
by some unreacted starting material. Continued elution gave
the photocycloaddition product 11 as a low melting solid
(90 mg, 30%). Further elution gave the compound 2
(105 mg, 35%) as a thick colorless liquid.
2. Banwell, M. G.; Edward, A. J.; Harfoot, G. J.; Jolliffe, K. A.
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3. Schuster, D. I. Rearrangements in Ground and Excited States;
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167–279.
Data for compound 2. IR (film) nmax: 1712 cmK1. 1H NMR
(400 MHz, CDCl3): d 5.79–5.71 (m, 2H), 3.16 (br s 1H),
2.85 (dd, JZ18.1, 9.3 Hz, 1H), 2.67 (d, JZ9.3 Hz, 1H),
2.62–2.49 (m, 2H), 2.38–2.22 (m, 1H), 2.15 (d, JZ18 Hz,
1H), 2.02–1.84 (m, 3H), 1.84–1.72 (m, 1H), 1.71–1.63 (m,
2H), 1.49–1.34 (m, 1H). 13C NMR (75 MHz, CDCl3C
CCl4): d 214.27, 133.64, 131.86, 58.48, 57.29, 52.69, 51.50,
50.24, 43.80, 42.50, 38.10, 27.60, 27.16, 26.48. HRMS:
223.1095 [MCNa], C14H16ONa requires 223.1093.
4. (a) Banwell, M. G.; Darmos, P.; McLeod, M. D.; Hockless,
D. C. R. Synlett 1998, 897–899. (b) Hagiwara, H.; Yamada, Y.;
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1
Data for caged product 11. IR (film) nmax: 1709 cmK1. H
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NMR (300 MHz, CDCl3): d 2.86–2.72 (merged m, 3H),
2.51 (br s, 1H), 2.44 (br s, 1H), 2.30 (d of part of an AB
system, JABZ17.7 Hz, J2Z3.3 Hz, 1H), 2.20 (br m, 1H),
2.10 (d of part of an AB system, JABZ17.7 Hz, J2Z2.3 Hz,
1H), 1.90–1.52 (merged m, 5H), 1.42–1.30 (m, 2H), 1.17–
1.04 (m, 1H). 13C NMR (75 MHz, CDCl3CCCl4): d 211.5,
54.0, 51.8, 48.4, 45.4, 44.4, 43.5, 40.3, 39.9, 38.9, 35.0,
31.9, 30.0, 27.2. HRMS: 201.1274 (MCCH) C14H16OCH
requires, 201.1279.
3.1.7. Tetracyclo[6.6.0.01,11.03,7]tetradec-4-en-10-one
(12). To a stirred solution of pentacyclic compound 2
(80 mg, 0.4 mmol) in dry benzene (10 mL) containing
AIBN (64 mg, 0.4 mmol), tributyltin hydride (0.44 mL,
1.5 mmol) was added and the reaction mixture was refluxed
for 6 h (TLC) under an atmosphere of nitrogen. Benzene
was removed and the residue was chromatographed on a
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Ugozzoli, F.; Vogt, W.; Wolff, A. J. Org. Chem. 1993, 58,
4023–4032. The compound 5 has been mentioned in this

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reference but the detailed procedure and data has not been
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