Synthesis of bicyclo[3.2.1]octanones via ketyl radical promoted rearrangements under reductive PET conditions

Article abstract of DOI:10.1016/j.tet.2007.08.054

Photoinduced electron transfer (PET) reactions from triethylamine (TEA) to ketones have been utilized for a clean and efficient route to bicyclo[3.2.1]octanones. A one-pot conversion of bicyclo[2.2.2]octenones to such molecules has been described. MeOH as

Full text of DOI:10.1016/j.tet.2007.08.054

Tetrahedron 63 (2007) 10979–10990
Synthesis of bicyclo[3.2.1]octanones via ketyl radical
promoted rearrangements under reductive PET conditions
*
Somnath Yadav, Srirupa Banerjee, Dwijendralal Maji and Saswati Lahiri
Department of Organic Chemistry, Indian Association for the Cultivation of Science, Kolkata 700 032, India
Received 9 June 2007; revised 30 July 2007; accepted 16 August 2007
Available online 22 August 2007
Abstract—Photoinduced electron transfer (PET) reactions from triethylamine (TEA) to ketones have been utilized for a clean and efficient
route to bicyclo[3.2.1]octanones. A one-pot conversion of bicyclo[2.2.2]octenones to such molecules has been described. MeOH as well as
acetonitrile/LiClO4 combinations have been found to be the most effective solvents for these reactions.
Ó 2007 Elsevier Ltd. All rights reserved.
1. Introduction
minimize BET, polar solvents are used for efficient solvation
of the ion pair at this stage leading to free radical ions, which
may then undergo ring cleavage in such strained rings (1).4
In terms of synthetic applications, photoinduced electron
transfer (PET) processes are becoming increasingly impor-
tant for constructing complex molecules because of their
chemo-, regio-, and diastereoselectivity.1 In one of the first
examples of the uses of PET for C–C bond cleavage reac-
tions Mattay and Bischof2 and Cossy et al.3 independently
reported the ring opening of fused a-keto small ring systems
using a carbonyl group as an acceptor (A) and an amine as
a donor (D). This process has also been successfully applied
for cyclopropyl bond cleavage of a-ketocyclopropanes
(Scheme 1).4,5
ET
-
+
-
+
A
D
A
D
A* +
D
*A
D
+
BET
SSIP
Free ions
ð1Þ
ET
-
+
A D
CIP
A* +
D
*A
D
BET
Depending on the better overlap of the cyclopropyl bond
(‘a’) with the ketyl radical anion, regioselective bond cleav-
age of 1 (R¼H or CH3) followed by hydrogen abstraction
from the solvent or from the amine then could give the final
product 2.5d The preferred regioselectivity of ring cleavage
(exo ‘a’ vs endo ‘b’) is also dependent on the substitution
pattern. Substitution of an electron-withdrawing group at
the C(b) position preferentially led to ‘b’-cleavage (endo)
because of better radical stabilizing effects.5a,6 Thus, under
PET conditions 1 (R1¼CO2Me) underwent ‘b’-cleavage giv-
ing the ring-expanded product 3 (Scheme 1).6 In the case of
tricyclo[3.3.0.02,8]octanone system 4 (R¼H), although the
stereoelectronic factor of maximum overlap governed the re-
gioselective cleavage of ‘a’ bond under PET conditions,7 the
corresponding diester derivative 4 (R¼CO2Me) yielded
a mixture (5:1) of the kinetically favored ‘a’-bond cleaved
product 5 (R¼CO2Me) and the thermodynamically favored
‘b’-bond cleaved product 6 (Scheme 2).8 Interestingly, such
reactions with a,a0-diketocyclopropanes-like ring-fused tri-
cyclo[3.3.0.02,8]octanones gave only ‘b’ bond cleaved prod-
ucts in moderate yields.8 Since bicyclo[3.2.1]octanes like 6
are very useful intermediates for the constructions of differ-
ent bioactive natural molecules9 and for their possible use as
O
O
O
R2
a
'a'
R2
R1
'b'
hν, 254 nm
hν, 254 nm
b
NEt3, MeCN
NEt3, MeCN
R1
2
1
CO2Me
3
R1 = CO2Me; R2 = H, CH3
R1 = H, CH3; R2 = H, CO2Me
Scheme 1.
The process (Eq. 1) involves a fast electron transfer from the
ground state of the amine (D) to the excited ketone (A),
which in solvent may then lead to a solvent separated ion
pair (SSIP). A contact radical ion pair (CIP) may also be
formed at this stage inside a solvent cage and both processes
may be in equilibrium. The overall process is a reversible
one and back electron transfer (BET) may lead to the initial
neutral states resulting in low conversion to products. To
Keywords: Bicyclo[3.2.1]octanones; Cyclopropyl ring cleavage; Photo-
induced electron transfer (PET).
* Corresponding author. E-mail: ocsl@iacs.res.in
0040–4020/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2007.08.054

10980
S. Yadav et al. / Tetrahedron 63 (2007) 10979–10990
phototriggers for liquid crystal-based optical switches,10 we
decided to explore this environment friendly PET
method with 1-aroyl substituted tricyclo[3.3.0.02,8]-
octanones (7a–g) for a convenient route to bicyclo[3.2.1]-
octanone systems.
Table 1. Chemical yields of formation of 7a–g in MeOH and benzene at
300 nm and quantum yields at 350 nm
Diene Adducta (%)
Photoproducts
Compd. Solvent, time (h) Yielda (%) (f)b
8a
8b
8c
9a (75)
9b (43)
9c (66)
7a
7b
7c
MeOH, 1.5
MeOH, 1.5
MeOH, 1.5
Benzene, 2
MeOH, 1.5
MeOH, 1.5
Benzene, 1
MeOH, 1.5
Benzene, 1
MeOH, 1.5
Benzene, 1
91
90
91
92
92
90
90
95
90
90
90
0.16
0.17
0.13c
R
R
8d
8e
9d (76)
9e (26)
7d
7e
0.27d
O
R
R
c
'a'
'b'
a
5
hν, 300 nm,
R=H or, CO2Me
b
O
NEt3/EtOH
8f
9f (72)
9g (80)
7f
0.37
0.26
H
CO2Me
CO2Me
4
8g
7g
O
6
a
Isolated yields.
In benzene.
For 7c fMeOH: 0.20 and f254: 0.13.
f254: 0.12.
R= CO2Me
b
c
d
Scheme 2.
2.2. Syntheses of tricyclo[3.3.0.02,8]octan-3-ones (7a–g)
where,
O
R1
R4
COPh
a: R1=R2=R3=R4=H
R4
R1
b: R1=CH3, R2=R3=R4=H
c: R1=R3=R4=H, R2=CH3
d: R1=R2=CH3, R3=R4=H
e: R1=R2=R4=H, R3=CH3
f: R1=R2=R3=H, R4=CH3
g: R1=R3=H, R2=R4=CH3
Tricyclo[3.3.0.02,8]octanones (7a–g) were readily obtained
from the photoisomerization of the corresponding bicy-
clo[2.2.2]octenones (9a–g). Photorearrangements of 9a–g
to 7a–g took place quantitatively (90–95%) within 2 h in
all types of solvents.
R4
O
R4
R3
2
R3
R3R
R2
R3
COPh
7a-g
9a-g
Better results were obtained using 300 and 350 nm lamps
compared to using 254 nm lamps. As we have observed ear-
lier for analogous cases,8,12 no sensitizer was needed for the
reaction to occur. A rapid inter-system crossing (ISC) was
assumed to have taken place in the excited state of com-
pound 9, which may be considered as either a d-keto-a,b-
enone or a d-keto-b,g-enone and its transformation to 7
may occur either via Type B rearrangement (a,b-enone)
or, via oxa-di-p-methane rearrangement (ODPM, b,g-
enone) (Scheme 4). At this stage it is difficult to differentiate
between the two routes. However, unlike other b,g-enones, 9
never gave 1,3-acyl-shift products and progressed without
sensitizer supporting the Type B route operating in the pres-
ent transformations. Further work toward this mechanistic
aspect is presently under progress. Confirmation that the
reactions involved triplet states was obtained by quenching
with a triplet quencher like anthracene.
Secondly, oxanorbornanones under PET conditions are
known to undergo cleavage of the oxa-bridge.1b Similar ob-
servations are not reported for analogous carbo-bicyclic
compounds. We wished to extend this PET method to aroyl
substituted bicyclo[2.2.2]octenone systems (9a–g) to
explore their possible bond cleavage–bond migration
reactions.
2. Results and discussion
2.1. Syntheses of bicyclo[2.2.2]oct-5-en-2-ones (9a–g)
5-Benzoyl-bicyclo[2.2.2]oct-5-en-2-ones (9a–g) were pre-
pared by the Diels–Alder reactions of suitably substituted
2-trimethylsilyloxycylohexa-1,3-dienes (8a–g) and 1-phe-
nylprop-2-yn-1-one (monobenzoylacetylene, MBA) follow-
ing a reported procedure (Scheme 3, Table 1).11,12,13 As
reported earlier,14 here also these additions of MBA were
found to be highly regioselective and the 1H NMR spectro-
scopic data of 9a–g confirmed the exclusive regioselectivity
of cycloadditions.
O
COPh
3π,π*
ODPM route
O
7a
Ph
O
O
hν
ISC
9a
O
3n,π*
O
R1
OSiMe3
R1
R4
R2
COPh
R1
R4
Type B route
R4
R4
i.
ii. H , MeOH
Ph
COPh
Ph
R4
R3
R3
hν
+
O
O
O
R2
R4
R3
3R2
COPh
R3 R3
8a-g
R
Scheme 4.
9a-g
7a-g
where,
2.3. Cyclopropyl ring cleavage under PET conditions
a: R1=R2=R3=R4=H; b: R1=CH3, R2=R3=R4=H; c: R1=R3=R4=H, R2=CH3;
d: R1=R2=CH3, R3=R4=H; e: R1=R2=R4=H, R3=CH3; f: R1=R2=R3=H,
R4=CH3; g: R1=R3=H, R2=R4=CH3
Following reported methods,2–6 when we had attempted cy-
clopropyl ring cleavage of 7c at 300 nm using a solution of
20% triethylamine (TEA) in acetonitrile, no significant
Scheme 3.

S. Yadav et al. / Tetrahedron 63 (2007) 10979–10990
10981
product formation was observed. Instead, use of a 40% solu-
tion of TEA in acetonitrile using 300 nm light for 1 h led to
exclusive formation of 10c in 62% yield along with 25% of
unreacted starting material (Scheme 5). The structure and
stereochemical assignment to 10c were based on detailed
spectroscopic analysis. In the IR spectrum there was a strong
peak at 1711 cmꢀ1 characteristic of a six-membered ketone,
which confirmed the cleavage of the ‘b’ bond in 7c. The pro-
ton at C8 appeared as a doublet (J5,8 4 Hz) at d 3.49 in the 1H
NMR spectrum, which confirmed its stereochemistry to be
anti to the ring carbonyl group.8,11,15 The 13C NMR spec-
trum showed signals due to one CH3, four CH2, two CH,
two C]O and one quaternary carbon in addition to the
aromatic signals.
with 254 nm yielded better results in these cases (Scheme 6).
The peak around 1705 cmꢀ1 in the IR spectrum confirmed the
presence of a six-membered ring in both the cases.
O
OSiMe3
i.
COCHMe2
ii. H+, MeOH
R
R
9h. i
COCHMe2
8a, c
hν
H
COCHMe2
40% TEA-MeOH
hν, 254 nm, 2 h
COCHMe2
O
R
R
7h, i
10h, i
O
H
COPh
where, h: R = H; i: R = Me
-
Ph
O
.
Scheme 6.
'a' or, 'b' or,
'c' or 'd'
7c
O
10c
2.4. Cyclopropyl ring cleavage using TBTH
O
a: hν, 300nm, 40% TEA-ACN; (62%, Recovered 7c:25%)
b: hν, 300nm, 40% TEA-ACN, LiClO4(1eq.); (80%)
c: hν, 300nm, 40% TEA-MeOH; (86%)
Use of tin hydride has been mostly a reagent of choice to
generate carbon centered radicals.17a,b Enholm and
coworkers employed tributyltin hydride (TBTH) to generate
O-stannyl ketyl radicals by single electron transfer (SET) to
promote the cleavage of cyclopropyl rings.18 Application of
this method to a tetracyclic ketone like 11 resulted in regio-
selective ‘b’ bond cleavage of the cyclopropyl ring.8 Tricy-
clic ketones like 7c,i when treated with n-Bu3SnH (TBTH)
and AIBN at 80 ꢂC for 3 h yielded the corresponding bicy-
clo[3.2.1]octanones 10c,i in 60% yields. Compound 7g un-
der the same reaction conditions generated an epimeric
mixture (4:1) of 10g and 100g (Scheme 7). An IR signal at
1709 cmꢀ1 confirmed the cleavage of the ‘b’ bond, which
gave a six-membered ketone. The stereochemistry of 100g
was confirmed from its 1H NMR spectrum where, like
reported similar systems,8,11,15 H-8 appeared as a singlet.
Although use of TBTH is one of the preferred methods for
generating radical centers, the toxicity of tin compounds
as well as difficulty to remove the residual tin derivatives
are the major drawbacks associated with this method.
d: n-Bu3SnH, AIBN, Bz, 80 °C; (60%)
Scheme 5.
In such carbinyl radical mediated cyclopropyl ring opening
reactions, use of LiClO4 as an additive has been reported to
accelerate an efficient formation of reductive ring-cleavage
products.5b,d On addition of LiClO4 the radical cation
ꢁ
Et3N+ is exchanged by Li+, which forms a tight ion pair
with the ketyl radical anion. Such an exchange process dis-
sociates the ketyl–amine radical ion pair and the bond migra-
tion can take place since proton transfer is delayed. Thus, the
above reaction when was carried out in the presence of
1 equiv LiClO4, the reaction was completed within 1 h and
10c was isolated in 80% yield.
Since PET reactions are known to be preferred in polar sol-
vents to avoid back electron transfer by stabilization of the
radical ions, the reaction was attempted using methanol.
Irradiation of 7c in 40% TEA–methanol for 1 h gave 10c
in 86% isolated yield. Methanol is more polar than acetoni-
trile and has been reported to give higher yields in electron-
transfer induced photo-allylation reactions.16 However, to
our knowledge, such preference for a polar protic solvent
like methanol over aprotic polar solvent like acetonitrile
has not been reported earlier for cyclopropyl ring cleavage
under PET conditions.
COPh
O
7g
TBTH / AIBN
80 °C
COPh
H
H
PhOC
The quantum yield of this reaction was found to be 0.16 in
MeOH and involvement of a triplet state was confirmed by
its quenching in the presence of oxygen and anthracene.
Addition of TEA quenched the phosphorescence of 7c
(428 nm), which confirmed the electron transfer to occur
between the triplet of 7c and TEA.
O
O
10'g, 15%
10g, 60%
Scheme 7.
The reaction worked well with acyl ketone substituted com-
pounds also. The diene 8a,c and 4-methylpent-1-yn-3-one
gave 9h,i, which on irradiation gave the tricyclic compounds
7h,i in quantitative yields. Under PET conditions 7h,i under-
went regioselective ring cleavage to give 10h,i and irradiation
2.5. One-pot conversion of bicyclo[2.2.2]octenones to
bicyclo[3.2.1]octanones
PET reactions between ketones and amines can generate
ketyl radical anions, which may lead to reductive bond

10982
S. Yadav et al. / Tetrahedron 63 (2007) 10979–10990
PhOC
H
O
R1
H
COPh
R1
R1
R1
COPh
R4
R4
R2
R4
R4
R3
R4
R4
40% TEA-MeOH
R4
R4
R3
R3
O
+
+
R3
hν, 300 nm, 1 h
COPh
R2
R2
10a,c,e,g
R3 3R2
R3
10'a,e,g
R3
R
7b,d,e,f,g
O
O
9a-g
where, a: R1=R2=R3=R4=H; b: R1=CH3, R2=R3=R4=H; c: R1=R3=R4=H, R2=CH3; d: R1=R2=CH3, R3=R4=H;
e: R1=R2=R4=H, R3=CH3; f: R1=R2=R3=H, R4=CH3; g: R1=R3=H, R2=R4=CH3
Scheme 8.
cleavage. This led us to explore the possibility of one-pot re-
ductive bond cleavage–bond formation reactions of 9c to
give 10c using such a method. Irradiation of 9c in 40%
TEA–methanol went very smoothly within 1 h to give 10c
in 86% yield (Scheme 8).
O
H
COPh
O
40% TEA-MeOH
hν, 300 nm, 1 h
COPh
12
11
hν
Similar results were obtained with the other bicy-
clo[2.2.2]octenones 9a,e–g leading to their quantitative con-
version to C-8 epimeric mixtures of bicyclo[3.2.1]octanones
10 and 100 along with small quantities of 7e–g (Scheme 8,
Table 2). The six-membered ketone in 10a was confirmed
by the nmax at 1711 cmꢀ1. Because of long range couplings
in the 1H NMR spectrum, the H-8 around d 3.57 appeared as
a multiplet, which coalesced to a triplet on irradiating one of
the acyl protons confirming syn-stereochemistry of the benz-
oyl group to the larger ring. As expected, in the epimer 100a
the H-8 at d 3.77 appeared as a singlet confirming its syn-ste-
reochemistry to the ring carbonyl group. The C-8 epimeric
relationship between 10a and 100a was confirmed by sodium
hydroxide catalyzed epimerization of the major isomer 10a,
which was then 80% converted to 100a. The products ob-
tained from 9e–f were identical and were identified as 10e
and 100e. In 10e the syn-stereochemistry of the multiplet
for H-8 around d 3.94 was confirmed by decoupling experi-
ments and the anti stereochemistry in 100e was confirmed
from the singlet at d 3.61. The anti-isomer 100e was found
to be the major product in this case. From 9g the major com-
pound was the syn isomer 10g whose stereochemistry was
again confirmed by decoupling experiments where the broad
doublet of H-8 around d 3.83 coalesced to a doublet on irra-
diating one of the acyl protons. In 100g, H-8 appeared as
a singlet at d 3.59.
COPh
20% TEA-MeOH
hν, 300 nm, 7 h
O
13
Scheme 9.
The conversion from 9c to 10c may take place via routes ‘a’
or, ‘b’ where the initially formed ketyl radicals A or B may
undergo bond formation (A0 or B0) or, bond migration (A00).
Bond migration followed by back electron transfer (BET)
from A0 and B0 may then lead to 7c, which may then undergo
PET mediated tandem bond migration to give 10c. Similar
oxa-di-p-methane rearrangement of ketyl radicals has also
been propsed for b,g-unsaturated aldehydes.19 Another
route via the rearranged product 7c (route ‘c’) may also
1
give 7c (Scheme 10). Although a time dependent H NMR
spectroscopic analysis of the reaction clearly showed in-
volvement of 7c at least at the earlier stage of reaction
(Fig. 1) suggesting ‘c’ as one of the routes, failure of the re-
action with 1-methyl substituted derivatives like 9b,d did not
rule out path ‘a’. Further, since a triplet state of the ketone is
likely to be quenched by the TEA present in the system,
direct conversion of 9c to 7c appeared to be less probable.
The reaction yielded 12-benzoyltricyclo[6.3.1.01,6]dodecan-
10-one (12) from 11-benzoyltricyclo[6.2.2.01,6]dodec-11-
en-9-one (11) in 78% yield within 1 h (Scheme 9) while
even the 4-benzoyltetracyclo[6.4.03,5.04,8]dodecan-6-one
(13) has been reported to yield no definite product even after
a short irradiation of 30 min in presence of 20% TEA–
MeOH mixture.8
The one-pot conversion of 5-isobutyryl derivative 7h needed
irradiation at 254 nm for a longer time (3 h) and resulted
in partial conversion to 8-isobutyrylbicyclo[3.2.1]octan-
3-one (10h, 36%) and 40% of the tricyclo derivative 7h.
Table 2. Yields of bicyclo[3.2.1]octanones by PET methods
The reaction did not work for 1-methyl substituted com-
pounds such as 9b and 9d. In the case of 9b, the reaction
gave a tarry mass from which no definite product could be
isolated. The reaction failed to give any isolable product
even from the corresponding cyclopropyl derivative 7b. Al-
though a short irradiation of 10 min of 7b, gave non-isolable
material, irradiation for a period of 5 min led to isolation of
2% of 10c (Table 2). In the case of 9d, the only product iso-
lated after 1 h was 43% of 7d along with 55% of unreacted
9d. The reactions of 9d as well as of 7d were also unsuccess-
ful with donors like dimethylaniline and DABCO.
Entry
Starting material
10 (%)
100 (%)
7 (%)
i
ii
9a
9b
1b
9c
7c
9d
9e
9f
10a (60)
Tarry mass
5c (2)
10c (86)
10c (62)
—
10e (17)
10e (20)
10g (69)
12 (78)
100a (33)
—
iii
iv
v
vi
vii
viii
ix
x
—
—
—
—
—
7d (43)
7e (6)
—
7g (7)
—
100e (70)
100e (69)
100g (7)
—
9g
11

S. Yadav et al. / Tetrahedron 63 (2007) 10979–10990
10983
O
O
O
or,
i. H+
ii H
Ph
A''
.
A'
Ph
Ph
A
-O
O
O
BET with
bond migration
'a' ET
H
COPh
O
COPh
i) ET; ii) H+;
iii) H
hν, 300nm, 1 h 'c'
O
40% TEA-MEOH
O
10c
COPh
9c
7c
BET with
bond migration
'b' ET
O
O
Ph
B'
COPh
B
O
Scheme 10.
7c
9c
9c
10c
7c
10c
c
7c
9c
9c
7c
b
10c
9c
7c
9c
7c
a
ppm 8
7
6
5
4
3
2
1
0
Fig. 1. 1H NMR spectra of the crude reaction mixture from the photolysis of 9c in 40% TEA–methanol after (a) 3 min (b) 6 min (c) 10 min.
Increase in irradiation time led to decreased yields via
decomposition.
75 MHz for 13C on a Brucker AC-300 spectrometer using
tetramethylsilane as an internal standard. Elemental analy-
ses were performed with a Heraeus Combustion apparatus
or on a 2400 series-II Perkin–Elmer CHN analyzer. High
Resolution Mass Spectra were recorded on a Qtof Micro
YA263 spectrometer. Flash Column Chromatography was
performed using silica gel (230–400 mesh) under medium
pressure and ordinary column chromatography was per-
formed using silica gel (60–120 mesh). Triethylamine was
distilled over KOH and solvents were purified, dried, and
distilled using reported procedures.20 Petroleum ether used
was of the boiling range 60–80 ꢂC. Ether refers to diethyl
ether. Irradiation experiments were carried out in a Rayonet
Photochemical Reactor using lamps of desired wavelength.
MBA,21 4-methylpent-1-yn-3-one,21 11-benzoyltricyclo-
[6.2.2.01,6]dodec-11-en-9-one22 were prepared following re-
ported procedures and the silyloxy-1,3-dienes were prepared
following a general procedure.23
3. Conclusion
From our results we found the PET mediated ring opening
of rigid cyclopropyl diketones are highly regioselective.
Since the commonly used organotin reagents are toxic
in nature and results in reduced yield because of difficulty
in removing the residual tin derivatives, these methods can
be used in its place for efficient generation of bicy-
clo[3.2.1]octanones.
4. Experimental
4.1. General
All melting points were measured in a Gallenkamp melting
point apparatus. The IR spectra were recorded on an FTIR-
8300 Shimadzu spectrometer. The NMR spectra were re-
corded in CDCl3 solution at 300 MHz for 1H and at
4.2. Syntheses of bicyclo[2.2.2]octenones (9a–g)
A mixture of suitable silyloxycyclohexa-1,3-diene and ace-
tylenic dienophile was stirred under argon atmosphere for

10984
S. Yadav et al. / Tetrahedron 63 (2007) 10979–10990
desired time after which 5% methanolic–HCl (5 mL) was
added to it and the mixture was stirred for 10 min. After re-
moval of MeOH the mixture was extracted with ether
(3ꢃ50 mL). The organic phases were combined, dried
over Na2SO4, and evaporated in vacuo. The residue was
chromatographed over a silica gel column.
1.62–1.94 (m, 4H), 2.10 (d, J 19 Hz, 1H), 2.27 (dd, J
19 and 2 Hz, 1H), 6.18 (s, 1H), 7.44–7.49 (m, 2H),
7.56–7.61 (m, 1H), 7.77–7.79 (m, 2H). 13C NMR:
d 17.1 (CH3), 21.7 (CH3), 31.9 (CH2), 34.5 (CH2), 39.8
(C), 47.3 (CH2), 50.3 (C), 128.2 (CH), 129.6 (CH),
132.9 (CH), 137.2 (C), 140.1 (CH), 149.0 (C), 194.5
(C]O), 211.2 (C]O). HRMS (ESI) calcd for
C17H18O2Na: 277.1204; found: [M+Na]+ 277.1216.
4.2.1. 5-Benzoylbicyclo[2.2.2]oct-5-en-2-one (9a). Mix-
ture of 8a (2.5 g, 14.85 mmol) and MBA (1.00 g,
7.69 mmol) was stirred for 3 h. Elution of the column with
10% ethyl acetate (EA) in petroleum ether (PE) gave a solid
of 6a (1.31 g, 75%), mp 88–90 ꢂC, as colorless crystals after
recrystallization from ether–PE (1:7) mixture. UV
(CH3CN): 252 nm (log 3 4.20), 285 (3.48), 342 (2.20). IR:
4.2.5. 5-Benzoyl-8,8-dimethylbicyclo[2.2.2]oct-5-en-2-
one (9e). Mixture of 8e (0.88 g, 4.48 mmol) and MBA
(0.44 g, 3.38 mmol) was heated at 50–60 ꢂC for 10 h. Elu-
tion of the column with 10% EA in PE gave a solid of 9e
(0.22 g, 26%), mp 76–78 ꢂC, as colorless crystals after re-
crystallization from ether–PE (1:7) mixture. UV: (CH3CN)
254 nm (log 3 4.39), 287 (3.69), 340 (2.58). IR: 1720,
1
1728, 1632 cmꢀ1. H NMR: d 1.62–2.25 (m, 6H), 3.39–
3.41 (m, 1H), 3.80–3.81 (m, 1H), 6.87 (dd, J 7 and 1 Hz,
1H), 7.43–7.48 (m, 2H), 7.53–7.58 (m, 1H), 7.69–7.71 (m,
2H). 13C NMR: d 23.0 (CH2), 24.2 (CH2), 32.1 (CH), 39.8
(CH2), 50.0 (CH), 128.3 (CH), 129.3 (CH), 132.3 (CH),
137.0 (C), 140.8 (CH), 147.1 (C), 193.0 (C]O), 211.0
(C]O). HRMS (ESI) calcd for C15H14O2Na: 249.0891;
found: [M+Na]+ 249.0895.
1
1641 cmꢀ1. H NMR: d 1.03 (s, 3H), 1.22 (s, 3H), 1.60
(dd, J 13 and 3 Hz, 1H), 1.80 (dd, J 13 and 2 Hz, 1H),
2.01 (dd, J 19 and 3 Hz, 1H), 2.54 (dd, J 19 and 2 Hz,
1H), 3.27–3.31 (m, 1H), 3.33–3.34 (m, 1H), 6.86 (dd, J 6
and 1 Hz, 1H), 7.43–7.48 (m, 2H), 7.54–7.59 (m, 1H),
7.70–7.73 (m, 2H). 13C NMR: d 28.2 (CH3), 31.2 (CH3),
33.5 (C), 35.9 (CH2), 38.6 (CH2), 43.4 (CH), 51.2 (CH),
128.2 (CH), 129.0 (CH), 132.0 (CH), 137.0 (C), 139.5
(CH), 148.2 (C), 192.9 (C]O), 210.9 (C]O). HRMS
(ESI) calcd for C17H18O2Na: 277.1204; found: [M+Na]+
277.1220.
4.2.2. 5-Benzoyl-1-methylbicyclo[2.2.2]oct-5-en-2-one
(9b). Mixture of 8b (4.46 g, 24.46 mmol) and MBA
(1.77 g, 13.61 mmol) was stirred for 4 h. Elution of the col-
umn with 12% EA in PE gave a solid of 9b (1.4 g, 43%), mp
94–96 ꢂC, as colorless crystals after recrystallization from
ether–PE (1:5) mixture. UV (CH3CN): 253 nm (log 3
4.2.6. 5-Benzoyl-7,7-dimethylbicyclo[2.2.2]oct-5-en-2-
one (9f). Mixture of 8f (3.5 g, 17.82 mmol) and MBA
(1.2 g, 9.23 mmol) was heated at 40 ꢂC for 10 h. Elution
of the column with 8% EA in PE gave a solid of 9f
(1.69 g, 72%), mp 103–105 ꢂC, as colorless crystals after re-
crystallization from ether–PE (1:6) mixture. UV (CH3CN):
254 nm (log 3 4.20), 287 (3.48), 340 (2.41). IR: 1717,
4.18), 293 (3.43), 338 (2.34). IR: 1724, 1639 cmꢀ1 1H
.
NMR: d 1.31 (s, 3H), 1.58–1.98 (m, 4H), 2.17 (dd, J 19
and 3 Hz), 2.25 (dd, J 19 and 2 Hz, 1H), 3.77–3.78 (m,
1H), 6.54 (d, J 2 Hz, 1H), 7.44–7.49 (m, 2H), 7.53–7.61
(m, 1H), 7.68–7.70 (m, 2H). 13C NMR: d 17.5 (CH3), 25.9
(CH2), 30.9 (CH2), 32.0 (CH), 39.8 (CH2), 51.1 (C), 128.4
(CH), 129.3 (CH), 132.3 (CH), 137.1 (C), 146.1 (CH),
146.9 (C), 193.0 (C]O), 211.7 (C]O). HRMS (ESI) calcd
for C16H16O2Na: 263.1048; found: [M+Na]+ 263.1044.
1
1638 cmꢀ1. H NMR: d 1.00 (s, 3H), 1.12 (s, 3H), 1.52–
1.58 (m, 1H), 1.70 (dd, J 13 and 3 Hz, 1H), 2.11–2.12 (m,
2H), 3.01 (d, J 7 Hz, 1H), 3.71–3.73 (m, 1H), 6.81 (dd, J 7
and 2 Hz, 1H), 7.42–7.46 (m, 2H), 7.52–7.57 (m, 1H),
7.67–7.70 (m, 2H). 13C NMR: d 30.2 (CH3), 30.7 (CH3),
32.5 (CH), 36.1 (C), 38.0 (CH2), 40.1 (CH2), 63.1 (CH),
128.2 (CH), 129.0 (CH), 132.2 (CH), 136.9 (C), 141.0
(CH), 146.0 (C), 192.7 (C]O), 210.7 (C]O). HRMS
(ESI) calcd for C17H18O2Na: 277.1204; found: [M+Na]+
277.1206.
4.2.3. 5-Benzoyl-4-methylbicyclo[2.2.2]oct-5-en-2-one
(9c). Mixture of 8c (2.5 g, 13.71 mmol) and MBA (0.9 g,
6.92 mmol) was stirred for 3 h. Elution of the column with
8% EA in PE gave a solid of 9c (2.32 g, 66%), mp 45–
47 ꢂC, as colorless crystals after recrystallization from
ether–PE (1:7) mixture. UV (CH3CN): 249 nm (log 3
4.22), 283 (3.44), 338 (2.16). IR: 1732, 1682 cmꢀ1 1H
.
NMR: d 1.43 (s, 3H), 1.68–1.86 (m, 3H), 2.07 (d, J 18 Hz)
mixed with 2.01–2.10 (m, total 2H), 2.23 (d, J 18 Hz, 1H),
3.32–3.35 (m, 1H), 6.50 (d, J 7 Hz, 1H), 7.43–7.48 (m,
2H), 7.56–7.61 (m, 1H), 7.78–7.80 (m, 2H). 13C NMR:
d 22.1 (CH3), 24.2 (CH2), 33.0 (CH2), 40.2 (C), 47.6
(CH2), 49.5 (CH), 128.5 (CH), 129.9 (CH), 133.1 (CH),
135.1 (CH), 137.3 (C), 149.5 (C), 194.9 (C]O), 211.0
(C]O). HRMS (ESI) calcd for C16H16O2Na: 263.1048;
found: [M+Na]+ 263.1049.
4.2.7. 5-Benzoyl-4,7,7-trimethylbicyclo[2.2.2]oct-5-en-2-
one (9g). Mixture of 8g (3 g, 14.26 mmol) and MBA
(1.40 g, 10.76 mmol) was stirred for 4 h. Elution of the col-
umn with 8% EA in PE gave a solid of 9g (2.32 g, 80%), mp
53–54 ꢂC, as colorless crystals after recrystallization from
ether–PE (1:7) mixture. Anal. Calcd for C18H20O2: C,
80.56; H, 7.51. Found: C, 81.15; H, 7.16. UV (CH3CN):
251 nm (log 3 4.14), 288 (3.33), 344 (2.30). IR: 1730,
1
1666 cmꢀ1. H NMR: d 1.04 (s, 3H), 1.13 (s, 3H), 1.39 (s,
3H), 1.54 (d, J 13 Hz, 1H), 1.63 (dd, J 13 and 3 Hz, 1H),
2.01 (d, J 18 Hz, 1H), 2.20 (dd, J 18 and 3 Hz, 1H), 2.95
(d, J 7 Hz, 1H), 6.47 (d, J 7 Hz, 1H), 7.43–7.48 (m, 2H),
7.55–7.60 (m, 1H), 7.77–7.81 (m, 2H). 13C NMR: d 22.4
(CH3), 30.5 (CH3), 31.2 (CH3), 37.4 (C), 41.0 (C), 46.3
(CH2), 49.8 (CH2), 62.9 (CH), 128.9 (CH), 130.2 (CH),
133.5 (CH), 136.0 (CH), 137.8 (C), 149.0 (C), 195.0
(C]O), 211.2 (C]O).
4.2.4. 5-Benzoyl-1,4-dimethylbicyclo[2.2.2]oct-5-en-2-
one (9d). Mixture of 8d, (1.65 g, 8.40 mmol) and MBA
(0.55 g, 4.23 mmol) was stirred under argon atmosphere
for 4 h. Elution of the column with 8% EA in PE gave
a thick liquid of 9d (0.82 g, 76%). UV (CH3CN):
250 nm (log 3 4.40), 280 (3.68), 338 (2.46). IR: 1724,
1651 cmꢀ1 1H NMR: d 1.29 (s, 3H), 1.42 (s, 3H),
.

S. Yadav et al. / Tetrahedron 63 (2007) 10979–10990
10985
4.2.8. 5-Isobutyrylbicyclo[2.2.2]oct-5-en-2-one (9h). Mix-
ture of 8a (2.2 g, 13.06 mmol) and 4-methylpent-1-yn-3-one
(0.94 g, 9.78 mmol) was stirred at 45 ꢂC for 4 h. Elution of
the column with 10% EA in PE gave a colorless liquid of
9h (1.10 g, 58%). Anal. Calcd for C12H16O2: C, 74.97; H,
8.39. Found: C, 74.87; H, 8.37. UV (CH3CN): 244 (log 3
48.6 (CH2), 50.9 (CH), 51.6 (C), 61.1 (C), 127.8 (CH),
128.7 (CH), 132.6 (CH), 138.4 (C), 199.2 (C]O), 212.4
(C]O). HRMS (ESI) calcd for C16H16O2Na: 263.1048;
found: [M+Na]+ 263.1045.
4.3.3. 1-Benzoyl-5-methyltricyclo[3.3.0.02,8]octan-3-one
(7c). Time: 1.5 h. Elution of the column with 10% EA in
PE gave 7c (91 mg, 91%), as thick liquid. UV (CH3CN):
246 nm (log 3 4.20), 281 (3.24), 311 (2.55). IR: 1726,
3.59), 296 (2.78), 338 (2.10). IR: 1734, 1666 cmꢀ1 1H
.
NMR: d 1.11(d, J 7 Hz, 3H), 1.13 (d, J 7 Hz, 3H), 1.43–
1.53 (m, 1H), 1.62–1.83 (m, 2H), 1.97 (ddd, J 19, 3 and
3 Hz) mixed with 1.92–2.03 (m, total 2H), 2.11 (dd, J 19
and 2 Hz, 1H), 3.23 (h, J 7 Hz, 1H), 3.35–3.39 (m, 1H),
3.72–3.75 (m, 1H), 7.12 (dd, J 7 and 2 Hz, 1H). 13C NMR:
d 19.1 (CH3), 19.2 (CH3), 22.7 (CH2), 23.8 (CH2), 30.2
(CH), 33.9 (CH), 39.4 (CH2), 49.7 (CH), 136.9 (CH),
146.8 (C), 201.1 (C]O), 211.2 (C]O).
1
1665 cmꢀ1. H NMR: d 1.21 (s, 3H), 1.70–1.86 (m, 3H),
2.13 (d, J 18 Hz, 1H), 2.28–2.40 (m, 2H), 2.47–2.56(m,
1H), 2.63 (d, J 18 Hz, 1H), 7.46–7.51 (m, 2H), 7.57–7.62
(m, 1H), 7.86–7.89 (m, 2H). 13C NMR: d 23.1(CH3), 24.7
(CH2), 36.5 (CH), 45.6 (CH), 48.4 (CH2), 49.3 (C), 54.7
(CH2), 55.9 (C), 128.7 (CH), 133.3 (CH), 137.6(C), 197.6
(C]O), 212.4 (C]O). HRMS (ESI) calcd for
C16H16O2Na: 263.1048; found: [M+Na]+ 263.1046.
4.2.9. 5-Isobutyryl-4-methylbicyclo[2.2.2]oct-5-en-2-one
(9i). Mixture of 8c (3.0 g, 16.46 mmol) and 4-methylpent-
1-yn-3-one (1.10 g, 11.45 mmol) was stirred at 45 ꢂC under
argon atmosphere for 4 h. Elution of the column with 8% EA
in PE gave a colorless liquid of 9i (1.30 g, 55%). Anal. Calcd
for C13H18O2: C, 75.69; H, 8.80. Found: C, 75.32; H, 8.57.
UV (CH3CN): 239 (log 3 3.70), 289 (2.04). IR: 1732,
At 350 nm:
solvent: benzene; time: 1.5 h. Yield of 7c: 91 mg, 91%,
solvent: MeOH; time: 1.5 h. Yield of 7c: 96 mg, 96%,
solvent: CH3CN; time: 1.5 h. Yield of 7c: 92 mg, 92%.
1
1678 cmꢀ1. H NMR: d 1.07 (d, J 7 Hz, 3H), 1.09 (d, J
7 Hz, 3H), 1.40 (s, 3H), 1.54–1.75 (m, 3H), 1.95 (d, J
18 Hz, 1H), 2.06 (d, J 18 Hz) mixed with 1.92–2.10 (m, total
3H), 3.06 (h, J 7 Hz, 1H), 3.27–3.30 (m, 1H), 6.77 (d, J 7 Hz,
1H). 13C NMR: d 18.1 (CH3), 18.5 (CH3), 22.5 (CH3), 23.9
(CH2), 33.0 (CH2), 37.5 (CH), 39.8 (C), 47.5 (CH2), 49.3
(CH), 133.5 (CH), 150.5 (C), 204.9 (C]O), 211.0 (C]O).
At 300 nm:
solvent: benzene; time: 2 h. Yield of 7c: 92 mg, 92%,
solvent: acetone; time: 1.5 h. Yield of 7c: 92 mg, 92%,
solvent: CH3CN; time: 1.5 h. Yield of 7c: 94 mg, 94%.
At 254 nm:
4.3. Photisomerization of 9a–g to tricyclo[3.3.0.02,8]-
octan-3-ones (7a–g)
solvent: benzene; time: 2 h. Yield of 7c: 84 mg, 84%,
solvent: MeOH; time: 2 h. Yield of 7c: 90 mg, 90%,
solvent: CH3CN; time: 2 h. Yield of 7c: 91 mg, 91%.
Unless otherwise stated, solutions of 9a–i (100 mg) in
MeOH (30 mL) were degassed with argon for 7 min and
then irradiated at 300 nm for specified time. The solvents
were removed in vacuo and the residues were chromato-
graphed over columns of silica gel (60–120 mesh).
4.3.4. 1-Benzoyl-5,8-dimethyltricyclo[3.3.0.02,8]octan-3-
one (7d). Time: 1.5 h. Elution of the column with 10%
EA in PE gave a thick liquid of 7d (92 mg, 92%). UV
(EtOH): 249 nm (log 3 4.01), 320 (2.20). IR: 1720,
1
4.3.1. 1-Benzoyltricyclo[3.3.0.02,8]octan-3-one(7a). Time:
1.5 h. Elution of the column with 12.5% EA in PE gave 7a
(91 mg, 91%), mp 64–66 ꢂC, as colorless crystals obtained
by recrystallization from ether–PE (1:6) mixture. UV
(CH3CN): 241 nm (log 3 4.08), 277 (3.02), 307 (2.50). IR:
1663 cmꢀ1. H NMR: d 1.12 (s, 3H), 1.19 (s, 3H), 1.63
(dd, J 6 and 6 Hz, 1H), 1.90–2.13 (m, 3H), 2.32–2.40 (m,
2H), 2.53 (d, J 18 Hz, 1H) 7.45–7.49 (m, 2H), 7.54–7.57
(m, 1H), 7.81–7.84 (m, 2H). 13C NMR: d 20.8 (CH3), 22.9
(CH3), 31.9 (CH2), 45.9 (C), 46.5 (CH2), 50.3 (CH), 50.4
(C), 55.3 (CH2), 60.2 (C), 128.59 (CH), 128.63 (CH),
133.1 (CH), 138.1 (C), 197.2 (C]O), 211.9 (C]O).
HRMS (ESI) calcd for C17H19O2: 255.1385; found:
[M+H]+ 255.1382.
1
1719, 1670 cmꢀ1. H NMR: d 1.67–1.86 (m, 2H), 1.96 (d,
J 18 Hz, 1H), 2.26–2.41 (m, 2H), 2.77–2.86 (m, 3H),
3.39–3.44 (m, 1H), 7.45–7.50 (m, 2H), 7.54–7.59 (m, 1H),
7.69–7.71 (m, 2H). 13C NMR: d 25.0 (CH2), 40.1 (CH),
40.2 (CH), 41.0 (CH2), 47.5 (CH2), 49.4 (CH), 57.7 (C),
127.8 (CH), 128.7 (CH), 132.5 (CH), 137.9 (C), 199.9
(C]O), 212.2 (C]O). HRMS (ESI) calcd for
C15H14O2Na: 249.0892; found: [M+Na]+ 249.0891.
4.3.5. 1-Benzoyl-6,6-dimethyltricyclo[3.3.0.02,8]octane-3-
one (7e). Time: 1.5 h. Elution of the column with 10% EA in
PE gave a white solid of 7e (90 mg, 90%), mp 71–73 ꢂC,
which was recrystallized from a mixture of ether–PE (1:5).
UV (CH3CN): 242 nm (log 3 3.70), 278 (2.65), 307 (2.12).
4.3.2. 1-Benzoyl-8-methyltricyclo[3.3.0.02,8]octan-3-one
(7b). Time: 1.5 h. Elution of the column with 10% EA in
PE gave a thick liquid of 7b (90 mg, 90%). UV (CH3CN)
242 nm (log 3 4.08), 278 (3.08), 313 (2.36). IR: 1724,
1
IR: 1730, 1663 cmꢀ1. H NMR: d 0.94 (s, 3H), 1.06 (s,
3H), 1.49 (dd, J 14 and 2 Hz, 1H), 1.85 (ddd, J 14, 7 and
2 Hz, 1H), 2.38 (d, J 18 Hz, 1H), 2.72 (d, J 18 Hz) mixed
with 2.66–2.75 (m, total 2H), 2.80–2.87 (m, 1H), 7.43–
7.48 (m, 2H), 7.52–7.55 (m, 1H), 7.63–7.66 (m, 2H). 13C
NMR: d 23.1 (CH3), 28.5 (CH3), 35.1 (CH), 37.8 (CH2),
42.2 (CH2), 49.6 (CH), 49.7 (CH), 49.8 (C), 57.4 (C),
127.3 (CH), 128.4 (CH), 132.1 (CH), 137.8 (C), 200.1
1
1657 cmꢀ1. H NMR: d 1.31 (s, 3H), 1.65–1.71 (m, 1H),
1.92 (d, J 18 Hz, 1H), 2.09–2.23 (m, 2H), 2.59–2.70 (m,
2H), 2.74 (s, 1H), 3.22 (dd, J 9 and 6 Hz, 1H) 7.47–7.52
(m, 2H), 7.56–7.61 (m, 1H), 7.75–7.77 (m, 2H). 13C
NMR: d 19.1 (CH3), 32.6 (CH2), 39.3 (CH2), 42.1 (CH),

10986
S. Yadav et al. / Tetrahedron 63 (2007) 10979–10990
(C]O), 212.0 (C]O). HRMS (ESI) calcd for C17H19O2:
255.1385; found: [M+H]+ 255.1354.
Anal. Calcd for C18H20O2: C, 80.56; H, 7.51. Found: C,
80.63; H, 7.32. UV (CH3CN): 247 nm (log 3 4.09), 280
1
(3.10), 317 (2.18). IR: 1717, 1657 cmꢀ1. H NMR: d 1.17
At 350 nm:
(s, 3H), 1.19 (s, 3H), 1.39 (s, 3H), 1.68 (d, J 13 Hz, 1H),
2.22 (dd, J 13 and 2 Hz, 1H), 2.25 (dd, J 10 and 2 Hz, 1H),
2.41 (d, J 18 Hz, 1H), 2.46 (br d, J 10 Hz, 1H), 2.71 (ddd, J
18, 2 and 2 Hz, 1H), 7.44–7.49 (m, 2H), 7.55–7.61 (m,
1H), 7.83–7.86 (m, 2H). 13C NMR: d 25.0 (CH3), 27.7
(CH3), 33.7 (CH3), 40.4 (C), 46.5 (CH), 49.9 (CH), 50.5
(C), 56.5 (CH2), 58.7 (C), 62.4 (CH2), 129.05 (CH), 129.07
(CH), 133.6(CH), 138.0 (C), 197.7 (C]O), 213.3 (C]O).
solvent: benzene; time: 1 h. Yield of 7e: 22 mg, 84% from
26 mg of 9e,
solvent: MeOH; time: 1 h. Yield of 7e: 24 mg, 92% from
26 mg of 9e,
solvent: CH3CN; Time: 1 h. Yield of 7e: 23 mg, 88%
from 26 mg of 9e.
At 300 nm:
At 350 nm:
solvent: benzene; time: 1 h. Yield of 7e: 18 mg, 90% from
20 mg of 9e,
solvent: acetone; time: 1 h. Yield of 7e: 18 mg, 90% from
20 mg of 9e.
solvent: benzene; time: 1.5 h. Yield of 7g: 91 mg, 91%,
solvent: MeOH; time: 1.5 h. Yield of 7g: 96 mg, 96%,
solvent: CH3CN; time: 1.5 h. Yield of 7g: 93 mg, 93%.
At 300 nm:
4.3.6. 1-Benzoyl-7,7-dimethyltricyclo[3.3.0.02,8]octan-3-
one (7f). Time: 1.5 h. Elution of the column with 7.5% EA
in PE gave a thick liquid of 7f (95 mg, 95%). UV
(CH3CN): 242 nm (log 3 4.16), 276 (3.15), 308 (2.56). IR:
solvent: benzene; time: 1.5 h. Yield of 7g: 93 mg, 93%,
solvent: acetone; time: 2 h. Yield of 7g: 96 mg, 96%,
solvent: CH3CN; time: 1.5 h. Yield of 7c: 93 mg, 93%.
1
1728, 1661 cmꢀ1. H NMR: d 1.20 (s, 3H), 1.34 (s, 3H),
1.61 (d, J 13 Hz, 1H), 2.22 (d, J 18 Hz, 1H), 2.42 (dd, J 13
and 7.5 Hz, 1H), 2.56 (d, J 10 Hz, 1H), 2.76 (d, J 10 Hz,
1H), 2.86 (dd, J 18 and 10 Hz, 1H), 3.44–3.49 (m, 1H),
7.46–7.51 (m, 2H), 7.55–7.60 (m, 1H), 7.70–7.73 (m, 2H).
13C NMR: d 27.9 (CH3), 33.3 (CH3), 41.0 (CH), 41.6 (C),
48.3 (CH), 49.5 (CH2), 53.9 (CH2), 54.0 (CH), 59.4 (C),
127.5 (CH), 128.6 (CH), 132.3 (CH), 137.6 (C), 199.7
(C]O), 212.6 (C]O). HRMS (ESI) calcd for C17H19O2:
255.1385; found: [M+H]+, 255.1382.
At 254 nm:
solvent: benzene; time: 2 h. Yield of 7g: 90 mg, 90%,
solvent: MeOH; time: 2 h. Yield of 7g: 92 mg, 92%,
solvent: CH3CN; time: 2 h. Yield of 7g: 88 mg, 88%.
4.3.8. 1-Isobutyryltricyclo[3.3.0.02,8]octan-3-one (7h).
Time: 2 h. Elution of the column with 10% EA in PE gave
7h (95 mg, 95%), mp 58–60 ꢂC, as colorless crystals on re-
crystallization from a mixture of ether–PE (1:6). Anal. Calcd
for C12H16O2: C, 74.97; H, 8.39. Found: C, 74.99; H, 8.29.
UV (CH3CN): 203 nm (log 3 3.97), 284 (2.38). IR: 1724,
At 350 nm:
1
solvent: benzene; time: 1 h. Yield of 7f: 17 mg, 85% from
20 mg of 9f,
solvent: MeOH; time: 1 h. Yield of 7f: 58 mg, 96% from
60 mg of 9f,
solvent: CH3CN; time: 1 h. Yield of 7f: 18 mg, 90% from
20 mg of 9f.
1678 cmꢀ1. H NMR: d 1.09 (d, J 6 Hz, 3H), 1.11 (d, J
6 Hz, 3H), 1.59–1.78 (m, 1H), 1.89 (d, J 18 Hz, 1H), 2.14–
2.30 (m, 3H), 2.68 (d, J 18 Hz) mixed with 2.56–2.79 (m, total
4H), 3.46–3.51 (m, 1H). 13C NMR: d 18.68 (CH3), 18.7(CH3),
24.7(CH2), 35.8(CH), 37.2(CH), 39.8(CH), 40.6 (CH2), 47.0
(CH2), 48.8 (CH), 57.8 (C), 210.2 (C]O), 211.9 (C]O).
At 300 nm:
At 350 nm:
solvent: benzene; Time: 1 h. Yield of 7f: 18 mg, 90%
from 20 mg of 9f,
solvent: acetone; time: 1 h. Yield of 7f: 17 mg, 85% from
20 mg of 9f.
solvent: benzene; time: 1.75 h. Yield of 7h: 90 mg, 90%,
solvent: MeOH; time: 1.75 h. Yield of 7h: 95 mg, 95%,
solvent: CH3CN; time: 1.75 h. Yield of 7h: 93 mg, 93%.
At 300 nm:
At 254 nm:
solvent: benzene; time: 2 h. Yield of 7h: 91 mg, 91%,
solvent: acetone; time: 2 h. Yield of 7h: 93 mg, 93%,
solvent: CH3CN; time: 1.5 h. Yield of 7c: 95 mg, 95%.
solvent: benzene; time: 2 h. Yield of 7f: 44 mg, 88% from
50 mg of 9f,
solvent: MeOH; time: 2 h. Yield of 7f: 45 mg, 90% from
50 mg of 9f,
At 254 nm:
solvent: CH3CN; time: 2 h. Yield of 7f: 46 mg, 92% from
50 mg of 9f.
solvent: benzene; time: 2 h. Yield of 7h: 86 mg, 86%,
solvent: MeOH; time: 2 h. Yield of 7h: 94 mg, 94%,
solvent: CH3CN; time: 2 h. Yield of 7h: 91 mg, 91%.
4.3.7. 1-Benzoyl-5,7,7-trimethyltricyclo[3.3.0.02,8]octan-
3-one (7g). Time: 1.5 h. Elution of the column with 10%
EA in PE gave 7g (95 mg, 95%), mp 60–61 ꢂC, as colorless
crystals after recrystallization from ether–PE (1:6) mixture.
4.3.9. 1-Isobutyryl-5-methyltricyclo[3.3.0.02,8]octan-3-
one (7i). Time: 2 h. Elution of the column with 10% EA in

S. Yadav et al. / Tetrahedron 63 (2007) 10979–10990
10987
PE gave 7i (90 mg, 90%), mp 52–54 ꢂC, as colorless crystals
on recrystallization from ether–petroleum ether (1:8). Anal.
Calcd for C13H18O2: C, 75.69; H, 8.80. Found: C, 75.49; H,
8.99. UV (EtOH): 290 nm (log 3 3.51). IR: 1732,
4.5.3. In methanol. Elution of the column with 8% EA in PE
gave a solid of 10c (28 mg, 86%) mp 58–60 ꢂC (mmp 58–
60 ꢂC).
1
1688 cmꢀ1. H NMR: d 1.05 (d, J 7 Hz, 6H), 1.55 (s, 3H),
4.6. Quantum yield for PET reaction of 7c to 10c
1.62–1.72 (m, 2H), 2.02 (d, J 18 Hz, 1H), 2.15–2.20 (m,
2H), 2.39 (h, J 7 Hz, 1H), 2.47 (d, J 18 Hz) mixed with
2.44–2.52 (m, total 2H), 2.62 (d, J 10 Hz, 1H). 13C NMR:
d 18.1(CH3), 18.5 (CH3), 23.2 (CH3), 24.0 (CH2), 36.3
(CH), 38.0 (CH), 47.0 (CH), 48.2(C), 48.4 (CH2), 54.8
(CH2), 55.7 (C), 209.2 (C]O), 211.2 (C]O).
A standard solution (about 3ꢃ10ꢀ3 M) of 7c was prepared in
40% TEA–methanol solution and subjected to 4 cycles of
freeze–pump–thaw process. From this, 10 mL aliquots
were irradiated in the presence of argon, oxygen, and anthra-
cene (about 1.5ꢃ10ꢀ2 M) in a Rayonet photoreactor at the
desired wavelength using a merry-go-round. The time of
irradiation for each set was so chosen so as to bring about
30–40% conversion of the starting material. The compara-
tive phototransformation (%) was calculated from NMR
spectra and quantum yields for product formations were
determined using uranyl oxalate as actinometer24 (4C O
4.4. Quantum yields for the phototransformations of
9a,c,d,f,g to7a,c,d,f,g
Standard solutions (about 3ꢃ10ꢀ3 M) of 9a,c,d,f,g were pre-
pared in benzene or methanol and subjected to 4 cycles of
freeze–pump–thaw. From these solutions, 10 mL aliquots
were irradiated in the presence of argon and anthracene
(about 1.5ꢃ10ꢀ2 M) in a Rayonet photoreactor at the desired
wavelength using a merry-go-round. The time of irradiation
for each set was so chosen so as to bring about 30–40% con-
version of the starting material. Comparative phototransfor-
mations (%) were calculated from NMR spectra and
quantum yields for product formations were determined us-
2
4
was 0.570 at 302 nm).
4.7. PET mediated cyclopropyl ring cleavage of 7h to
8-isobutyrylbicyclo[3.2.1]octan-3-one (10h)
The above procedure was carried out with 1-isobutyryl-
tricyclo[3.3.0.02,8]octan-3-one (7h, 100 mg, 0.52 mmol)
in dry methanol (24 mL) and TEA (16 mL) using
254 nm lamps in a pyrex tube for 3 h. Elution of the col-
umn with 5% EA in PE gave a thick liquid of 10h (40 mg,
ing uranyl oxalate as actinometer (4C O was 0.468 at
4
350 nm and 0.602 at 254 nm)24 (Table 1)2.
1
40%). IR: 1703 cmꢀ1. H NMR: d 1.15 (d, J 7 Hz, 6H),
4.5. PET mediated cyclopropyl ring cleavage of 7c to
8-benzoyl-1-methylbicyclo[3.2.1]octan-3-one (10c)
1.59 (dd, J 16 and 7 Hz, 2H), 1.89–1.93 (m, 2H), 2.22
(d, J 16 Hz, 2H), 2.72–2.85 (m, 4H), 2.87 (h, J 7 Hz)
2.92–2.94 (m, 1H), 2.73–2.94 (m, total 6H). 13C NMR:
d 18.6 (CH3), 29.5 (CH2), 37.1 (CH), 40.4 (CH), 46.2
(CH2), 54.2 (CH), 211.6 (C]O), 215.7 (C]O). HRMS
(ESI) calcd for C12H18O2Na: 217.1205; found [M+Na]+
217.1245.
To a solution of 1-benzoyl-5-methyltricyclo[3.3.0.02,8]-
octan-3-one (7c, 30 mg, 0.13 mmol) in dry solvent (6 mL)
was added TEA (4 mL) and the resulting solution was de-
gassed with argon for 7 min. This solution was then irradi-
ated with 300 nm lamp in a pyrex tube for 1 h, after which
the volatile components were removed by distillation over
a water bath under reduced pressure. The resulting mixture
was then flash chromatographed over a column of silica.
Further elution of the column with 7.5% EA in PE gave
a solid of unreacted 7h (35 mg, 35%) mp 58–60 ꢂC (mmp
59 ꢂC).
4.5.1. In acetonitrile. Elution of the column with 8% EA in
PE gave a solid of 10c (20 mg, 62%), mp 58–60 ꢂC, as color-
less crystals after recrystallization from ether–PE (1: 8) mix-
ture. Anal. Calcd for C16H18O2: C, 79.31; H, 7.49. Found C,
4.8. PET mediated cyclopropyl ring cleavage of 7i to
8-isobutyryl-5-methylbicyclo[3.2.1]octan-3-one (10i)
The above procedure was carried out with 1-isobutyryl-
5-methyltricyclo[3.3.0.02,8]octan-3-one
1
79.74; H, 7.60. IR: 1711, 1670 cmꢀ1. H NMR: d 1.19 (s,
(7i,
46 mg,
3H), 1.51–1.60 (m, 1H), 1.66–1.71 (m, 2H), 2.13 (br d, J
17 Hz), and 2.16 (br d, J 17 Hz), mixed with 2.06–2.19
(m, total 3H), 2.43 (br d, J 17 Hz, 1H), 2.82 (hextet, J
4 Hz, 1H), 3.40 (br d, J 17 Hz, 1H), 3.49 (d, J 4 Hz, 1H),
7.48–7.53 (m, 2H), 7.58–7.63 (m, 1H), 7.97–7.99 (m, 2H).
13C NMR: d 24.9 (CH3), 28.8 (CH2), 38.6 (CH2), 39.5
(CH), 44.2 (C), 44.9 (CH2), 52.0 (CH2), 55.2 (CH), 128.0
(CH), 128.8 (CH), 133.3 (CH), 137.9 (C), 201.6 (C]O),
211.7 (C]O).
0.22 mmol) in dry methanol (9 mL) and TEA (6 mL) using
254 nm lamps in a pyrex tube for 2.5 h. Elution of the col-
umn with 5% EA in PE gave a thick liquid of 10i (35 mg,
1
77%). IR: 1707 cmꢀ1. H NMR: d 1.11 (s, 3H), 1.12 (d, J
7 Hz, 3H), 1.14 (d, J 7 Hz, 3H), 1.46–1.62 (m, 3H), 2.01
(ddd, J 17, 2 and 2 Hz) mixed with 1.94–2.03 (m, total
2H), 2.20 (br d, J 16 Hz, 1H), 2.47 (ddd, J 16, 3 and 3 Hz,
1H), 2.76 (h, J 7 Hz) mixed with 2.68–2.73 (m, total 2H),
2.81–2.83 (m, 1H), 3.17 (dd, J 17 and 2 Hz, 1H). 13C
NMR: d 18.1 (CH3), 18.8 (CH3), 25.3 (CH3), 29.4 (CH2),
38.5 (CH2), 39.0 (CH), 42.4 (CH), 44.6 (C), 45.3 (CH2),
52.2 (CH2), 58.4 (CH), 211.9 (C]O), 216.7 (C]O).
HRMS (ESI) calcd for C13H20O2Na: 231.1361; found
[M+Na]+ 231.1360.
Further elution of the column with 8% EA in PE gave back
unreacted starting material 7c (8 mg, 25%, superimposed
spectra).
4.5.2. In acetonitrile and LiClO4. The above procedure was
repeated in the presence of LiClO4 (14 mg, 1 equiv). Chro-
matographic separation using 8% EA in PE gave a solid of
10c (26 mg, 80%) mp 58–60 ꢂC (mmp 58–60 ꢂC).
Further elution of the column with 7.5% EA in PE gave
a solid of unreacted 7i (10 mg, 22%) mp 52–54 ꢂC (mmp
52–54 ꢂC).

10988
S. Yadav et al. / Tetrahedron 63 (2007) 10979–10990
4.9. TBTH mediated cyclopropyl ring cleavages of 7c,g,i
to 10c,g,i
NMR: d 18.1 (CH3), 18.8 (CH3), 25.3 (CH3), 29.4 (CH2),
38.5 (CH2), 39.0 (CH), 42.4 (CH), 44.6 (C), 45.3 (CH2),
52.2 (CH2), 58.4 (CH), 211.9 (C]O), 216.7 (C]O).
HRMS (ESI) calcd for C13H20O2Na: 231.1361; found:
[M+Na]+ 231.1360.
To the solutions of the tricyclic compounds (100 mg) and
AIBN (catalytic) in 15 mL benzene at 80 ꢂC, TBTH
(2 equiv) was slowly added dropwise via a syringe. The re-
sulting mixture was refluxed at 80 ꢂC for further 3 h after
which the mixture was cooled and the solvent was removed
at reduced pressure. The residue was hydrolyzed by stirring
overnight with dilute HCl (5 mL), after which the mixture
was worked up with ether and dried over anhydrous
Na2SO4. The solvent was then removed and the residue
was chromatographed over a column of silica gel.
Further elution of the column with 10% ethyl acetate in
petroleum ether gave back unreacted starting material 7i
(15 mg, 15%) mp 52–54 ꢂC (mmp 52–54 ꢂC).
4.10. PET mediated conversion of bicyclo[2.2.2]octenones
to bicylo[3.2.1]octanones
A solution of the bicyclo-compounds (150 mg) in methanol
(30 mL) containing (20 mL) TEA, was degassed by purging
with argon for 7 min. The solution was then irradiated in
a pyrex tube at 300 nm for 1 h under argon after which the
volatile materials were removed under reduced pressure.
The residue was then purified by flash chromatography
over a column of silica gel (230–400 mesh) to yield the
products.
4.9.1. 8-Benzoyl-1-methylbicyclo[3.2.1]octan-3-one (10c)
from 7c. Elution of the column with 8% EA in PE gave col-
orless crystals of 10c (60 mg, 60%) mp 58–60 ꢂC (mmp 58–
60 ꢂC).
4.9.2. 8-Benzoyl-1,6,6-trimethylbicyclo[3.2.1]octan-3-
ones (10g,100g) from 7g. Elution of the column with 10%
ethyl acetate in petroleum ether gave 10g (60 mg, 60%),
mp 64–66 ꢂC, as colorless crystals after recrystallization
from ether–petroleum ether (1:4) mixture. Anal. Calcd for
C18H22O2: C, 79.96; H, 8.20. Found C, 80.18; H, 8.03. IR:
4.10.1. Conversion of 5-benzoylbicyclo[2.2.2]oct-5-en-2-
one (9a). Elution of the column with 7.5% EA in PE gave
8-benzoylbicyclo[3.2.1]octan-3-one (10a, 90 mg, 60%) as
a white solid after recrystallization from ether–PE (1:4) mix-
ture, mp 95–97 ꢂC. Anal. Calcd for C15H16O2: C, 78.92; H,
1
1709, 1670 cmꢀ1. H NMR: d 1.01 (s, 3H), 1.18 (s, 3H),
1.31 (s, 3H), 1.50 (d, J 13 Hz, 1H), 1.60 (dd, J 13 and
3 Hz, 1H), 2.16 (br d, J 18 Hz, 1H), 2.18 (dd, J 18 and
4 Hz, 1H), 2.33 (q, J 4 Hz, 1H), 2.42 (br d, J 18 Hz, 1H),
3.45 (dd, J 18 and 3 Hz, 1H), 3.83 (br d, J 4 Hz, 1H),
7.47–7.52 (m, 2H), 7.57–7.62 (m, 1H), 7.94–7.97 (m, 2H).
13C NMR: d 27.7 (CH3), 28.3 (CH3), 35.8 (CH3), 41.4 (C),
42.9 (CH2), 46.4 (C), 52.3 (CH), 54.4 (CH2), 56.5 (CH),
57.5 (CH2), 130.2 (CH), 130.9 (CH), 135.4 (CH), 139.9
(C), 203.4 (C]O), 214.1 (C]O). HRMS (ESI) calcd for
C18H23O2: 271.1698; found [M+H]+ 271.1661.
1
7.06. Found: C, 78.38; H, 7.06. IR: 1711, 1668 cmꢀ1. H
NMR: d 1.66 (dd, J 15 and 7 Hz, 2H), 2.02–2.06 (m, 2H),
2.22 (br d, J 16 Hz, 2H), 2.89 (br d, J 16 Hz) mixed with
2.86 (br m, total 4H), 3.56–3.59 (m, 1H), 7.47–7.52 (m,
2H), 7.57–7.62 (m, 1H), 7.95–7.97 (m, 2H). 13C NMR:
d 29.4 (CH2), 37.5 (CH), 45.9 (CH2), 51.8 (CH), 127.9
(CH), 128.6 (CH), 133.0 (CH), 137.2 (C), 201.3 (C]O),
211.6 (C]O). HRMS (ESI) calcd for C15H17O2:
229.1229; found: [M+H]+ 229.1235.
Further elution of the column with 10% ethyl acetate in pe-
troleum ether gave the other 8-epimer (100g, 15 mg, 15%),
mp 67–69 ꢂC, as colorless crystals after recrystallization
from ether–petroleum ether (1: 8) mixture. Anal. Calcd for
C18H22O2: C, 79.96; H, 8.20. Found C, 79.91; H, 8.24. IR:
Further elution of the column with 7.5% EA in PE gave
a white solid of the other 8-epimer 100a (50 mg, 33%), which
was recrystallized from ether–PE (1:4) mixture, mp 67–
69 ꢂC. Anal. Calcd for C15H16O2: C, 78.92; H, 7.06. Found:
C, 78.65; H, 7.15. IR: 1713, 1674 cmꢀ1. 1H NMR: d 1.53–
1.60 (m, 2H), 2.00–2.03 (m, 2H), 2.47 (dd, J 18 and 2 Hz,
2H), 2.65 (br d, J 18 Hz, 2H), 2.86 (br m, 2H), 3.77 (s,
1H), 7.48–7.53 (m, 2H), 7.58–7.62 (m, 1H), 7.99–8.02 (m,
2H). 13C NMR: d 28.3 (CH2), 38.3 (CH), 50.4 (CH2), 57.1
(CH), 128.3 (CH), 128.7 (CH), 133.1 (CH), 135.6 (C),
200.0 (C]O), 211.0 (C]O). HRMS (ESI) calcd for
C15H17O2 229.1229; found [M+H]+ 229.1245.
1
1713, 1682 cmꢀ1. H NMR: d 0.94 (s, 3H), 0.97 (s, 3H),
1.33 (s, 3H), 1.55 (dd, J 13 and 1 Hz, 1H), 2.30 (d, J
13 Hz, 1H), 2.36 (dd, J 4 and 3 Hz, 1H), 2.42 (s, 2H), 2.65
(dd, J 17 and 4 Hz, 1H), 2.81 (dd, J 17 and 3 Hz, 1H),
3.59 (s, 1H), 7.47–7.52 (m, 2H), 7.56–7.62 (m, 1H), 7.94–
7.97 (m, 2H). 13C NMR: d 23.0 (CH3), 28.8 (CH3), 32.5
(CH3), 41.0 (C), 44.1 (C), 47.9 (CH2), 50.7 (CH), 52.3
(CH2), 59.0 (CH2), 61.6 (CH), 128.1 (CH), 128.7 (CH),
133.0 (CH), 137.0 (C), 201.0 (C]O), 211.3 (C]O).
HRMS (ESI) calcd for C18H23O2: 271.1698; found:
[M+H]+ 271.1695.
4.10.2. Conversion of 5-benzoyl-4-methylbicyclo[2.2.2]-
oct-5-en-2-one (9c). Elution of the column with 7.5% EA
in PE gave 8-benzoyl-1-methylbicyclo[3.2.1]octan-3-one
(10c, 130 mg, 86%) as a white solid, which was recrystal-
lized from ether–PE (1:4) mixture, mp 58–60 ꢂC (mmp
58–60 ꢂC).
4.9.3. 8-Isobutyryl-1-methylbicyclo[3.2.1]octan-3-one
(10i) from 7i. Elution of the column with 7% ethyl acetate
in petroleum ether gave a thick liquid of 10i (60 mg,
1
60%). IR: 1707 cmꢀ1. H NMR: d 1.11 (s, 3H), 1.12 (d, J
4.10.3. Conversion of 5-benzoyl-1,4-dimethylbicy-
clo[2.2.2]oct-5-en-2-one (9d). Elution of the column with
7.5% EA in PE gave 9d (82 mg, 55%, superimposed spec-
tra). Further elution of the column with 7.5% EA in PE
gave 1-benzoyl-5,8-dimethyltricyclo[3.3.0.02,8]octan-3-one
(7d, 64 mg, 43%, superimposed spectra).
7 Hz, 3H), 1.14 (d, J 7 Hz, 3H), 1.46–1.62 (m, 3H), 2.01
(ddd, J 17, 2 and 2 Hz) mixed with 1.94–2.03 (m, total
2H), 2.17 (br d, J 16 Hz, 1H), 2.47 (ddd, J 16, 3 and 3 Hz,
1H), 2.76 (h, J 7 Hz) mixed with 2.68–2.73 (m, total 2H),
2.81–2.83 (m, 1H), 3.17 (dd, J 17 and 2 Hz, 1H). 13C

S. Yadav et al. / Tetrahedron 63 (2007) 10979–10990
10989
4.10.4. Conversion of 5-benzoyl-8,8-dimethylbicy-
clo[2.2.2]oct-5-en-2-one (9e). Elution of the column with
7.5% EA in PE gave 8-benzoyl-6,6-dimethylbicy-
clo[3.2.1]-octan-3-one (10e, 30 mg, 17%) as a white solid,
which was recrystallized from ether–PE (1:4) mixture, mp
59–61 ꢂC. Anal. Calcd for C17H20O2: C, 79.65; H, 7.86.
Further elution of the column with 7.5% EA in PE gave
a white solid of the 8-epimer 100g (10 mg, 7%), mp 67–
69 ꢂC (mmp 67–69 ꢂC).
4.10.7. Conversion of 5-isobutyrylbicyclo[2.2.2]oct-5-en-
2-one (9h). Time: 4 h. Elution of the column with 5% EA
in PE gave 8-isobutyrylbicyclo[3.2.1]octan-3-one (10h,
55 mg, 36%) as a thick liquid (superimposible spectra).
1
Found: C, 79.51; H, 7.92. IR: 1707, 1668 cmꢀ1. H NMR:
d 1.06 (s, 3H), 1.26 (s, 3H), 1.41 (d, J 14 Hz, 1H), 1.92
(ddd, J 14, 7 and 3 Hz, 1H), 2.23 (br d, J 18 Hz, 1H),
2.35–2.38 (m, 1H), 2.46 (br d, J 18 Hz, 1H), 2.61 (dd, J 18
and 4 Hz, 1H), 2.83–2.85 (m, 1H), 3.03 (ddd, J 18, 3 and
3 Hz, 1H), 3.92–3.95 (m, 1H), 7.46–7.52 (m, 2H), 7.56–
7.59 (m, 1H), 7.92–7.95 (m, 2H). 13C NMR: d 26.2 (CH3),
32.8 (CH3), 37.6 (CH), 39.8 (C), 41.8 (CH2), 46.0 (CH2),
46.1 (CH2), 48.3 (CH), 50.8 (CH), 127.8 (CH), 128.6
(CH), 133.0 (CH), 137.2 (C), 201.5 (C]O), 211.7
(C]O). HRMS (ESI) calcd for C17H21O2: 257.1542; found
[M+H]+ 257.1538.
Further elution with 7.5% EA in PE gave a solid of 1-isobu-
tyryltricyclo[3.3.0.02,8]octan-3-one (7h, 60 mg, 40%) mp
58–60 ꢂC (mmp 58–60 ꢂC).
4.10.8. Conversion of 11-benzoyltricyclo[6.2.2.01,6]do-
dec-11-en-9-one (11). The procedure was repeated with 11
(70 mg, 0.25 mmol) in dry MeOH (15 cc) and TEA
(10 cc). Elution of the column with 7.5% EA in PE gave
12-benzoyltricyclo[6.3.1.01,6]dodecan-10-one (12, 55 mg,
78%) mp 122–124 ꢂC (lit.11 mp 124 ꢂC) as a white solid,
which was recrystallized from ether–PE (1:4) mixture.
Further elution of the column with 7.5% EA in PE gave a
white solid of 1-benzoyl-6,6-dimethyltricyclo[3.3.0.02,8]-
octan-3-one (7e, 10 mg, 6%), which was recrystallized
from ether–PE (1:5) mixture, mp 71–73 ꢂC (superimposed
spectra).
4.11. Epimerisation of 8-benzoylbicyclo[3.2.1]octan-3-
one (10a)
To a solution of (10a, 50 mg, 0.22 mmol) in 5 cc MeOH,
methanolic NaOH solution (10%, 5 cc) was added and the
mixture was stirred at room temperature for 12 h. After
which the mixture was extracted with ether (3ꢃ15 cc). The
combined extracts were washed with brine till neutral, dried
over anhydrous Na2SO4. The solvent was then removed
under reduced pressure and the residue was column chroma-
tographed. Elution with 10% EA in PE gave the epimeric
8-benzoylbicyclo[3.2.1]octan-3-one (100a, 40 mg, 80%)
mp 67–69 ꢂC, mmp 67–69 ꢂC.
Further elution of the column with 7.5% EA in PE gave
a white solid of the other 8-epimer 100e (120 mg, 70%),
which was recrystallized from ether–PE (1:5) mixture, mp
1
69–71 ꢂC. IR: 1705, 1682 cmꢀ1. H NMR: d 0.78 (s, 3H),
0.97 (s, 3H), 1.43 (d, J 14 Hz, 1H), 2.19 (dd, J 14 and
7 Hz, 1H), 2.53–2.54 (m, 3H), 2.66 (dd, J 17 and 4 Hz,
1H), 2.77 (dd, J 17 and 3 Hz, 1H), 3.09–3.10 (m, 1H),
3.61 (s, 1H), 7.48–7.52 (m, 2H), 7.57–7.62 (m, 1H), 7.95–
7.97 (m, 2H). 13C NMR: d 28.0 (CH3), 32.3 (CH3), 35.8
(CH), 40.6 (C), 44.7 (CH2), 47.6 (CH2), 50.4 (CH2), 50.8
(CH), 59.1 (CH), 128.2 (CH), 128.6 (CH), 132.9 (CH),
135.9 (C), 201.1 (C]O), 211.6 (C]O). HRMS (ESI) calcd
for C17H20O2Na: 279.1361; found [M+Na]+ 279.1349.
References and notes
€
1. Some of the recent reviews are: (a) Oelgemoller, M.;
4.10.5. Conversion of 5-benzoyl-7,7-dimethylbicy-
clo[2.2.2]oct-5-en-2-one (9f). Elution of the column with
7.5% EA in PE gave 8-benzoyl-6,6-dimethylbicy-
clo[3.2.1]octan-3-one (10e, 40 mg, 20%) as a white solid,
which was recrystallized from ether–PE (1:4), mp 59–
61 ꢂC (mmp 59–61 ꢂC).
Griesbeck, A. G. CRC Handbook of Organic Photochemistry
and Photobiology; Horsepool, W. M., Lenci, F., Eds.; CRC:
Boca Raton, FL, 2004; p 84-1; (b) Cossy, J. Radicals in
Organic Synthesis; Renaud, P., Sibi, M. P., Eds.; Wiley-VCH:
Weinheim, 2001; Vol. 1, p 229; (c) Albini, A.; Fagnoni, M.;
Mella, M. Pure Appl. Chem. 2000, 72, 1321; (c) Santamaria,
J. Pure Appl. Chem. 1995, 67, 141.
Furtherelutionofthecolumnwith7.5%EAinPEgaveathick
liquid of 1-benzoyl-7,7-dimethyltricyclo[3.3.0.02,8]octan-3-
one (7f, 10 mg, 5%, superimposed spectra).
2. (a) Bischof, E. W.; Mattay, J. Tetrahedron Lett. 1990, 31, 7137;
(b) Bischof, E. W.; Mattay, J. J. Photochem. Photobiol. A:
Chem. 1992, 63, 249.
3. Cossy, J.; Aclinou, P.; Bellosta, V.; Furet, N.; Sparfel, D.;
Souchoud. Tetrahedron Lett. 1991, 32, 1315.
4. (a) Mattay, J.; Vondenhof, M. Top. Curr. Chem. 1991, 159, 219;
(b) Mattay, J. Synthesis 1989, 233; (c) Mattay, J. Angew. Chem.,
Int. Ed. Engl. 1987, 26, 825.
Further elution of the column with 7.5% EA in PE gave
a white solid of the other 8-epimer 100e (140 mg, 69%) mp
69–71 ꢂC (mmp 69–71 ꢂC).
4.10.6. Conversion of 5-benzoyl-4,7,7-trimethylbicy-
clo[2.2.2]oct-5-en-2-one (9g). Elution of the column with
7.5% EA in PE gave colorless crystals of 8-benzoyl-1,6,6-
trimethylbicyclo[3.2.1]octan-3-one (10g, 120 mg, 79%)
mp 64–66 ꢂC (mmp 64–66 ꢂC).
5. (a) Cossy, J.; Bellotti, D. Tetrahedron 2006, 62, 6459; (b)
Tzvetkov, N. T.; Neumann, B.; Stammler, H. G.; Mattay, J.
Eur. J. Org. Chem. 2006, 351; (c) Kirschenberg, T.; Mattay,
J. J. Org. Chem. 1996, 61, 8885; (d) Cossy, J.; Furet, N.;
BouzBouz, S. Tetrahedron 1995, 51, 11751.
6. Cossy, J.; Furet, N. Tetrahedron Lett. 1993, 34, 8107.
7. Pandey, B.; Rao, A. T.; Dalvi, P. V.; Kumar, P. Tetrahedron
1994, 50, 3843.
Further elution ofthe columnwith 7.5%EA inPE gave awhite
solid of 1-benzoyl-5,7,7-trimethyltricyclo[3.3.0.02,8]octan-3-
one (7g, 10 mg, 7%) mp 60–61 ꢂC (mmp 60–61 ꢂC).
8. Maiti, B. C.; Lahiri, S. Tetrahedron 1998, 54, 9111.

10990
S. Yadav et al. / Tetrahedron 63 (2007) 10979–10990
9. Filippini, M.-H.; Rodriguez, J. Chem. Rev. 1999, 99, 27.
10. Zhang, Y.; Schuster, G. B. J. Org. Chem. 1995, 60, 7192.
11. Maiti, B. C.; Lahiri, S. Tetrahedron 1997, 53, 13053.
12. Maiti, B. C.; Singh, R.; Lahiri, S. J. Photochem. Photobiol. A:
Chem 1995, 91, 27.
13. Formation of 9e was found to be extremely sluggish, which we
attributed to a possible steric effect exerted by the 5,5-dimethyl
group of the diene 8e.
Formation of Carbon–Carbon Bonds; Pergamon: New York,
NY, 1996.
18. (a) Enholm, E. J.; Zia, Z. J. J. Org. Chem. 1997, 62, 174; (b)
Enholm, E. J.; Zia, Z. J. J. Org. Chem. 1997, 62, 5248; (c)
Enholm, E. J.; Jia, Z. J. Tetrahedron Lett. 1995, 36, 6819.
19. Armesto, D.; Ortiz, M. J.; Agarrabeitia, A. R.; Martin-
Fontecha, M. Org. Lett. 2004, 6, 2261.
20. Perrin, D. D.; Armarego, W. L. F.; Perin, D. R. Purification of
Laboratory Chemicals; Pergamon: Oxford, 1980.
21. Naito, T.; Nkagawa, S.; Okumura, J. U.S. Patent 3,360,527,
1967; Chem. Abstr. 1968, 69, 36117.
14. Lahiri, S.; Yadav, S.; Chanda, M.; Chakraborty, I.; Chowdhury,
K.; Mukherjee, M.; Roy Chowdhury, A.; Guru Row, T. N.
Tetrahedron Lett. 2005, 46, 8133.
15. Yates, P.; Stevens, K. E. Tetrahedron 1981, 37, 4401.
16. Nishigaichi, Y.; Suzuki, A.; Takuwa, A. Tetrahedron Lett.
2005, 46, 211.
17. (a) Curran, D. P. Comprehensive Organic Synthesis; Trost,
B. M., Fleming, I., Eds.; Pergamon: New York, NY, 1992;
Vol. 4; (b) Giese, B. Radicals in Organic Syntheses:
22. Maiti, B. C.; Sinha, R.; Lahiri, S. J. Chem. Res., Synop. 1993,
500.
23. (a) Rubottom, G. M.; Krueger, D. S. Tetrahedron Lett. 1977, 611;
(b) Rubottom, G. M.; Cruber, J. M. J. Org. Chem. 1977, 42, 1051.
24. Murov, S. L. Handbook of Photochemistry; Marcel Dekker:
New York, NY, 1973; p 124.