Palladium-catalysed synthesis of nonsymmetrically disubstituted-1,1′- biphenyls from o-substituted aryl iodides through aryl coupling and delayed hydrogenolysis

Article abstract of DOI:10.1139/v05-084

In the presence of Pd(OAc)₂ and norbornene as catalysts, two molecules of an ortho-substituted aryl iodide undergo aryl-aryl coupling to a palladium-bonded biphenylyl intermediate, which is hydrogenolyzed by benzyl alcohol to give 2,3′-disubsti

Full text of DOI:10.1139/v05-084

741
Palladium-catalysed synthesis of
nonsymmetrically disubstituted-1,1′-biphenyls
from o-substituted aryl iodides through aryl
coupling and delayed hydrogenolysis1
Sara Deledda, Elena Motti, and Marta Catellani
Abstract: In the presence of Pd(OAc)2 and norbornene as catalysts, two molecules of an ortho-substituted aryl iodide
undergo aryl–aryl coupling to a palladium-bonded biphenylyl intermediate, which is hydrogenolyzed by benzyl alcohol
to give 2,3′-disubstituted biaryl derivatives in satisfactory yields. A curious behaviour was observed with o-
chloroiodobenzene, which gave activation of the C—Cl bond with four-membered ring formation.
Key words: biphenyls, aryl–aryl coupling, multistep reactions, palladium, palladacycles, C-H activation, catalysis.
Résumé : En présence de Pd(OAc)2 et de norbornène agissant comme catalyseurs, deux molécules d’iodure d’aryle
substituées en ortho subissent une réaction de couplage aryle–aryle conduisant à un intermédiaire biphénylyle lié au
palladium qui peut subir une réaction d’hydrogénolyse sous l’action de l’alcool benzylique pour conduire à la forma-
tion de dérivés biaryles 2,3′-disubstitués, avec des rendements satisfaisants. On a observé un comportement bizarre avec
l’o-chloroiodobenzène donne lieu à une activation de la liaison C—Cl avec formation d’un cycle à quatre membres.
Mots clés : biphényles, couplage aryle–aryle, réactions en plusieurs étapes, palladium, palladacyles, activation C-H, ca-
talyse.
[Traduit par la Rédaction] Deledda et al. 747
Introduction
erentially migrates on the norbornyl site of the palladacycle
(pathway b) (18).
Biphenyls are an important class of organic compounds,
the biphenyl unit being the building block of several types of
structures of current interest, including natural products,
polymers, advanced materials, liquid crystals, ligands, and
drugs (1).
The most successful catalytic methods in biphenyl synthe-
sis are based on palladium catalysis (2–7). We used a cata-
lytic system involving palladacycles (8–13). Different types
of the latter have been extensively studied by several groups
(14–17).
According to our methodology, aryl–aryl coupling
through palladacycles occurs regioselectively. As shown in
the simplified Scheme 1 (L = solvent or coordinating mole-
cule), these palladacycles are formed by the reaction of an
aryl iodide with palladium(0) and norbornene. In the pres-
ence of an ortho-R substituent (alkyl, aryl, and other func-
tional groups), the palladacycle reacts selectively with the
aryl iodide to form an sp2–sp2 carbon–carbon bond at the
aryl site (pathway a), while the remaining norbornylpalla-
dium bond readily deinserts norbornene to afford a biphenyl-
ylpalladium complex (18). By contrast, when the R
substituent is H or a small group like F, the aryl group pref-
Causing the biphenylylpalladium complex to undergo a
reaction able to liberate the organic product and palla-
dium(0) renders the process catalytic. In this way the synthe-
sis of a variety of interesting classes of organic compounds
such as selectively substituted phenanthrenes (19), terphenyls
(20), and biphenyl derivatives containing an oxoalkyl (21) or
a vinyl (22) chain has been achieved.
We now report a catalytic synthesis of 2,3′-disubstituted-
1,1′-biphenyls, based on the combination of the stoichio-
metric sequence leading to the biphenylylpalladium species
with a delayed hydrogenolysis reaction.
Results and discussion
As shown in Scheme 2, two molecules of an ortho-
substituted aryl iodide and one of a hydrogen donor react in
the presence of Pd(OAc)2 and norbornene as catalysts, and
K2CO3 as a base in a dipolar aprotic solvent such as 1-
methyl-2-pyrrolidinone (NMP) at 105 °C for 24 h to give
2,3′-disubstituted-1,1′-biphenyls (1).
The main difficulty for the achievement of this synthesis
laid in obtaining an efficient hydrogenolysis of the
Received 8 December 2004. Published on the NRC Research Press Web site at http://canjchem.nrc.ca on 23 June 2005.
S. Deledda, E. Motti, and M. Catellani.2 Dipartimento di Chimica Organica e Industriale and CIRCC, Parco Area delle Scienze,
17/A, 43100 Parma, Italy.
1This article is part of a Special Issue dedicated to Professor Howard Alper.
2Corresponding author (e-mail: marta.catellani@unipr.it).
Can. J. Chem. 83: 741–747 (2005)
doi: 10.1139/V05-084
© 2005 NRC Canada

742
Can. J. Chem. Vol. 83, 2005
Scheme 1.
Table 1. Reaction of o-i-propyliodobenzene and a H donor in the
presence of K2CO3, norbornene, and Pd(OAc)2.a
R
L
R
Run
Hydrogen donor
Biphenyl 1 yield (%)b
I
+ Pd0L2 +
1
2
3
4
5
6
Benzyl alcohol
Benzydrol
Butanol
Isobutyl formate
Sodium formate
Water
86
84
75
72
21
37, 77c
Pd
R
L
I
R
I
R = H
pathway b
R
L
R
pathway a
H
aMolar ratio of the reagents o-i-propyliodobenzene : H donor : K2CO3 :
norbornene : Pd(OAc)2 = 80:80:160:20:1 at 105 °C for 24 h in NMP un-
der nitrogen; 2 × 10–3 mmol Pd(OAc)2 /mL NMP.
R
I
Pd
-
R
bGC yield on the charged amount of the aryl iodide.
cWater to palladium molar ratio: 2.5 × 102.
L
Pd
L
Scheme 3.
I
R
R
R
L
1
R
R
L
R
R
+ PhCHO
I
R
Pd
Pd
L
L
I
L
Pd0L2
I
Pd
OCH2Ph
R
L
2
Scheme 2.
7
R
R
I
PhCH2OH
Pd(OAc)2,
2
+ H donor
R
K2CO3, NMP
105 °C, 24 h
R
R
L
1
Pd
I
Pd
I
R
L
L
biphenylylpalladium species without interfering with the
previous steps. To effect hydrogenolysis, two main methods
were available: hydrogenation of the C-Pd-I bond with
dihydrogen and hydrogen transfer from suitable sources. In
principle, with both methods a selectivity problem could be
expected since hydrogenolysis can occur at any step of the
sequence. However, while hydrogenation with dihydrogen at
atmospheric pressure gave a nonselective outcome, the ap-
propriate use of the hydrogen transfer methodology led to
delayed hydrogenolysis to the end of the catalytic sequence
with good selectivity.
Among the combination of palladium sources, solvents,
and bases examined, Pd(OAc)2, NMP, and K2CO3 proved to
be the most effective. The norbornene to aryl iodide molar
ratio was found to play an important role, better results be-
ing obtained when using a ratio as low as 0.25 equiv. The re-
action of o-isopropyliodobenzene (80 equiv.) with different
hydrogen donors (80 equiv.) was thus carried out in the pres-
ence of Pd(OAc)2 (1 equiv.), K2CO3 (160 equiv.),
norbornene (20 equiv.) in NMP at 105 °C for 24 h under ni-
trogen. Various hydrogen donors were tested in a 1:1 molar
ratio to o-isopropyliodobenzene as the substrate. Table 1 re-
ports the yield of the biphenyl 1 (Scheme 2, R = i-Pr) ob-
tained. Among the examined hydrogen sources, benzyl
3
6
K2CO3
KI
R
L
R
L
R
R
I
Pd
L
I
Pd
4
5
alcohol and benzhydrol appear the most effective ones (Ta-
ble 1, runs 1 and 2). Butanol (Table 1, run 3) and isobutyl
formate (Table 1, run 4) behave analogously affording satis-
factory results, while sodium formate (23) (Table 1, run 5)
gives a low yield because of the formation of products re-
sulting from Pd-C hydrogenolysis of the intermediate com-
plexes 3 and 4 reported in Scheme 3. Water also is effective
(Table 1, run 6) but only if used in large excess (2.5 × 102
molar ratio to palladium) otherwise the reaction leads to
© 2005 NRC Canada

Deledda et al.
743
Table 2. Reaction of ortho-substituted aryl iodides and benzyl al-
Scheme 4.
cohol in the presence of K2CO3, norbornene, and Pd(OAc)2.a
R
R
L
Run
Aryl iodide
Biphenyl 1 yield (%)b
a)
1
2
3
4
5
6
7
o-MeC6H4I
72
84
79
83
87
48
78
+ Pd0L2
o-EtC6H4I
Pd
o-n-BuC6H4I
o-i-PrC6H4I
o-MeO2CC6H4I
o-MeOC6H4I
L
8
4
HX
b)
I
R
R
L
L
L
aMolar ratio of the reagents in the order reported in the title:
80:80:160:20:1 at 105 °C for 24 h in NMP, N2 atmosphere; 2 ×
10–3 mmol Pd(OAc)2/mL NMP.
Pd
L
Pd
X
bIsolated yield on the charged aryl iodide. Conversion was complete.
R
poor results. An aryl iodide to benzyl alcohol molar ratio of
1:1 was found to be optimal, an excess of benzyl alcohol be-
ing detrimental.
Scheme 3 shows the proposed reaction pathway. The cata-
lytic cycle is initiated by the oxidative addition of the o-sub-
stituted aryl iodide to palladium(0) formed in situ by
Pd(OAc)2 reduction. Norbornene insertion into the resulting
arylpalladium complex 2 occurs stereoselectively leading to
the cis,exo arylnorbornylpalladium species 3 (24–28). In the
presence of a base such as K2CO3, the open precursor under-
goes ring closure to 4 (10–13) through an electrophilic aro-
matic substitution (11) facilitated by an η2-interaction of
palladium with one double bond of the aromatic ring (25,
28). Palladacycle formation implies activation of an usually
inert aromatic C—H bond (29–31). Because of the presence
of the ortho substituent in the aromatic ring of palladacycle
4, a second molecule of aryl iodide selectively attacks the ar-
omatic moiety of the same palladacycle 4 affording complex
5, which deinserts norbornene with formation of the
biphenylylpalladium species 6 (18). At this stage, complex 6
reacts with benzyl alcohol to give 7, which promotes hydro-
gen transfer via a Pd-H intermediate to form biphenyl 1 to-
gether with palladium(0) and benzaldehyde.
Table 2 reports the results obtained carrying out the reac-
tion with an o-substituted aryl iodide (80 equiv.), benzyl al-
cohol (80 equiv.), palladium acetate (1 equiv.), norbornene
(20 equiv.), and potassium carbonate (160 equiv.) in NMP
under nitrogen at 105 °C for 24 h. Satisfactory results were
obtained with different primary and secondary alkyl groups
as well as with electron-withdrawing substituents (Table 2,
runs 1–5) while the presence of an electron-releasing group
such as the methoxy one (Table 2, run 6) led only to poor
results. 1-Iodonaphthalene (Table 2, run 7) behaved as an
ortho-substituted arene, which is a requirement for the aryl
coupling to occur, and gave acceptable yields.
+ Pd0L2
9
palladacycle 4, after hydrogenolysis of the norbornyl-
palladium bond, inserts a new molecule of norbornene in the
resulting Pd–aryl bond to form 9 according to pathway b of
Scheme 4. Compound 8 also derives from palladacycle 4 as
shown in Scheme 4. The steric effect of the ortho substituent
favours reductive elimination to compound 8, containing a
four-membered ring (pathway a) (32), in place of the reac-
tion with a second molecule of aryl iodide. By-products 8
and 9 were usually formed with a yield from 1% to 5%.
A 5,9-disubstituted 1,2,3,4,4a,12b-hexahydro-1,4-methan-
otriphenylene derivative of type 10 (33, 34), was usually
formed to a large extent when the hydrogen donor became
deficient owing to secondary reactions. As shown in
Scheme 5, 10 derives from complex 5, which, in the absence
of an efficient terminating agent, prefers to undergo
reductive elimination by ring closure instead of norbornene
deinsertion.
As previously reported, if R is a methyl group, two addi-
tional by-products resulting from activation of the benzylic
C-H (35) were formed to a small extent (5%).
Anomalous behaviours were observed with o-chloro- and
o-fluoroiodobenzene.
o-Chloroiodobenzene, used in a 40:1 molar ratio to palla-
dium, gave poor conversion (28%) and only a small amount
(6%) of 1 was formed. The main product was the hexa-
hydromethanobiphenylene derivative 11 (15%), which de-
rives from C—Cl bond activation (Scheme 6). This result is
surprising not only because it implies activation of an usu-
ally inert C—Cl bond, but also because it should be regarded
as involving the C—Cl bond of the norbornyl-bonded o-
By-products result from hydrogen transfer to intermediate
complexes. The hydrogen donor mostly reacts with the spe-
cies containing a norbornyl– rather than an aryl–palladium
bond. In particular, arylnorbornylpalladium iodide 3 is readily
hydrogenolysed to the corresponding arylnorbornane and
© 2005 NRC Canada

744
Can. J. Chem. Vol. 83, 2005
Scheme 5.
Scheme 7.
R
F
F
R
I
F
PdIL2
R
-Pd0L2, -HI
I
Pd
Pd
L
R
L
L
F
5
F
F
10
L
L
F
Scheme 6.
Pd
Cl
F
+ Pd0L2
Cl
12
Cl
I
Pd
-PdIClL2
L
Experimental
11
General
5 (R = Cl)
All reactions were carried out under a nitrogen atmo-
sphere, using standard Schlenk techniques. Most chemicals
were obtained commercially and used as received. Com-
pounds 1 (R = Me (36), Et (37), OMe (38), CO2Me (39),
-(CH)4- (40), Cl (41)), 8 (R = Me, OMe (32), Et, n-Bu, i-Pr
(42), -(CH)4- (43)), 9 (R = Me, Et, n-Bu, i-Pr (20), -(CH)4-
(43)), and 12 (22) were previously reported. 1H and 13C
NMR spectra were carried out in CDCl3 at 20 °C using
Bruker AC300 and AVANCE300 spectrometers at 300.1 and
75.4 MHz, respectively. Chemical shifts are reported in ppm
using the solvent as the internal reference. The assignments
of NMR resonances are based on decoupling and 2D experi-
ments; one or more asterisks indicates interchangeable as-
signments. Mass spectra (EI) were recorded using a
Finnigan Mat SSQ 710 spectrometer operating at 70 eV and
are reported as m/z (relative intensity). IR spectra were run
on a PerkinElmer 298 FT-IR spectrophotometer and are re-
ported as wavenumbers (cm–1). GC analyses were performed
with a Carlo Erba HRGC 5300 instrument using a 30 m long
SE-30 capillary column and a Hewlett-Packard 3394 integra-
tor. Flash column chromatography was performed on Merck
Kieselgel 60 and analytical TLC on Merck 60F254 plates.
Melting points were determined on an Electrothermal appa-
ratus and are uncorrected. Elemental analyses were per-
formed with a Carlo Erba EA 1108 elemental analyser.
chloroaryl group of complex 5 (Scheme 6), C—Cl bond ac-
tivation occurring only in the presence of a second o-
chloroaryl unit. The alternative formation of a type 10 com-
pound does not occur. The origin of this behaviour is proba-
bly to be attributed to a Pd-Cl interaction that favours C-Cl
activation, thus preventing not only formation of a type 10
compound but also norbornene deinsertion.
As previously reported (22), the different reactivity of the
F group is likely to be ascribed to the small size of the fluo-
rine atom. The latter is not large enough to give “the ortho
effect”, which would cause the formation of the aryl–aryl
bond of intermediate 5 by reaction of palladacycle 4 with o-
fluoroiodobenzene (Scheme 3, R = F), and so the ortho-
fluorophenyl group migrates to the norbornyl site of the
palladacycle. Ring closure to hexahydromethanotriphenylene
does not occur, however, because of the deactivation of the
aromatic nucleus towards the arylpalladium electrophilic at-
tack and norbornene is instead inserted. The reaction thus
terminates with the formation of the hexahydromethanobi-
phenylene 12 in 67% yield, as reported in Scheme 7.
Conclusion
Reaction of o-substituted aryl iodides with benzyl
In conclusion, the catalytic method we have worked out
offers a ready access to nonsymmetrically disubstituted bi-
phenyls starting from two molecules of an o-substituted aryl
iodide and represents a useful alternative to the Suzuki reac-
tion and to other organometallic processes. The failure of o-
fluoroiodobenzene to give the expected reaction confirms the
need for a sufficiently bulky group ortho to iodobenzene,
while the observation that the usually unreactive arene C—
Cl bond is readily cleaved shows that competitive steps
readily occur in sequential reactions when usually inert
bonds are forced into the appropriate position for the inter-
action with the metal.
alcohol
General procedure
A mixture of Pd(OAc)2 (5 mg, 0.022 mmol), K2CO3
(498 mg, 3.6 mmol), the desired aryl iodide (1.8 mmol),
norbornene (42 mg, 0.45 mmol), and benzyl alcohol
(195 mg, 1.8 mmol) in NMP (10 mL) under nitrogen was
heated at 105 °C with stirring for 24 h. The mixture was
cooled to room temperature, diluted with CH2Cl2 (20 mL),
and extracted twice with a 5% solution of H2SO4 (2 ×
15 mL). The organic layer was washed with water (20 mL)
and dried over anhydr. Na2SO4. The crude product was ana-
© 2005 NRC Canada

Deledda et al.
745
lysed by GC, GC–MS, and TLC. Products were isolated by
flash column chromatography using hexane or mixtures of
hexane–EtOAc as the eluents. By-product yields were deter-
mined by GC analysis.
23.57 (CH3CH(C5)). MS m/z (%): 330 (M+, 63), 262 (25),
245 (26), 205 (76), 203 (39), 202 (37), 179 (100). Anal.
calcd. for C25H30: C 90.85, H 9.15; found: C 90.98, H 9.02.
2,3′-Di-n-butyl-1,1′-biphenyl (1, R = n-Bu)
The reaction was carried out following the general proce-
dure using 469 mg (1.8 mmol) of o-n-butyliodobenzene.
Compound 1 (R = n-Bu) was isolated as a colourless oil in
79% yield (190 mg) by column chromatography, using hex-
ane as the eluent. Compounds 8 (R = n-Bu) (42) and 9 (R =
n-Bu) (20) were formed in 4% and 3% yield, respectively.
2,3′-Dimethyl-1,1′-biphenyl (1, R = Me)
The reaction was carried out following the general proce-
dure using 393 mg (1.8 mmol) of o-iodotoluene. Compound
1 (R = Me) (36) was isolated as a colourless oil in 72% yield
(118 mg) by column chromatography, using hexane as the
eluent. Compounds 8 (R = Me) (32) and 9 (R = Me) (20)
were formed in 2% and 3% yield, respectively, together with
two by-products resulting from the activation of the benzylic
C—H bond (35) (2% yield each) and exo,o-tolylnorbornane
(4%) (44) resulting from hydrogenolysis of complex 3 (R =
Me).
1 (R = n-Bu)
1H NMR δ: 7.35–7.27 (3H, m), 7.24–7.20 (2H, m), 7.19–
7.09 (3H, m), 2.66 (2H, t, J = 7.6 Hz), 2.61–2.54 (2H, m),
1.70–1.57 (2H, m), 1.57–1.30 (6H, m), 1.30–1.09 (2H, m),
0.94 (3H, t, J = 7.3 Hz), 0.80 (3H, t, J = 7.3 Hz). 13C NMR
δ: 142.44, 142.03, 141.85, 140.35, 129.94, 129.40, 129.18,
127.79, 127.14, 126.77, 126.46, 125.42, 35.61, 33.65, 32.74,
22.53, 22.29, 13.96, 13.83. MS m/z (%): 266 (M+, 39), 223
(20), 209 (22), 180 (16), 178 (16), 167 (100), 152 (10).
Anal. calcd. for C20H26: C 90.19, H 9.84; found: C 90.28, H
9.75.
2,3′-Diethyl-1,1′-biphenyl (1, R = Et)
The reaction was carried out following the general proce-
dure using 418 mg (1.8 mmol) of o-ethyliodobenzene. Com-
pound 1 (R = Et) (37) was isolated as a colourless oil in
84% yield (159 mg) by column chromatography, using hex-
ane as the eluent. Compounds 8 (R = Et) (42) and 9 (R = Et)
(20) were formed in 4% and 5% yield, respectively.
2,3′-Dimethoxycarbonyl-1,1′-biphenyl (1, R = CO2Me)
The reaction was carried out following the general proce-
dure using 472 mg (1.8 mmol) of methyl o-iodobenzoate.
Compound 1 (R = CO2Me) (39) was isolated as a solid in
87% yield (212 mg) by flash chromatography, using hexane –
CH2Cl2 – ethyl acetate (7:2.5:0.5) as the eluent. Compounds
8 (R = CO2Me) and 10 (R = CO2Me) were formed in 5%
and 4% yield, respectively.
2,3′-Di-i-propyl-1,1′-biphenyl (1, R = i-Pr)
The reaction was carried out following the general proce-
dure using 443 mg (1.8 mmol) of o-i-propyliodobenzene.
Compound 1 (R = i-Pr) was isolated as a white solid in 83%
yield (178 mg) by column chromatography, using hexane as
the eluent. Compounds 8 (R = i-Pr) (42), 9 (R = i-Pr) (20),
and 10 (R = i-Pr) were formed in 5%, 3%, and 2% yield, re-
spectively.
1 (R = CO2Me)
1H NMR δ: 8.07–8.00 (2H, m, H4′, H2′), 7.89 (1H, dd,
J = 7.7, 1.5 Hz, H3), 7.55 (1H, td, J = 7.5, 1.5 Hz, H5),
7.52–7.45 (2H, m, H5′, H6′), 7.44 (1H, td, J = 7.6, 1.4 Hz,
H4), 7.37 (1H, dt, J = 7.6, 1.4 Hz, H6), 3.92 (3H, s,
CO2CH3), 3.64 (3H, s, CO2CH3). 13C NMR δ: 168.49 (q),
166.95 (q), 141.67 (q), 132.88 (C6′), 131.52 (C5), 130.79
(C6), 130.40 (q), 130.11 (C3), 129.99 (q), 129.43 (C2′),
128.39 (C4′), 128.00 (C5′), 127.61 (C4), 52.15 (CO2CH3),
51.98 (CO2CH3). MS m/z (%): 270 (M+, 83), 239 (71), 207
(100), 181 (29), 180 (23), 152 (44), 151 (43), 76 (29). Anal.
calcd. for C16H14O4: C 71.10, H 5.22; found: C 71.37, H
5.19.
1 (R = i-Pr)
1H NMR δ: 7.44–7.30 (3H, m), 7.27–7.16 (4H, m), 7.13
(1H, dt, J = 7.4, 1.4 Hz), 3.07, 2.96 (2H, 2 hept. partly over-
lapping, J = 6.9 Hz), 1.30 (6H, d, J = 6.9 Hz), 1.18 (6H, d,
J = 6.9 Hz). 13C NMR δ: 148.45, 146.38, 141.98, 141.40,
129.91, 127.82, 127.52, 126.66, 125.53, 125.22, 124.82,
34.06, 29.37, 24.34, 24.02. MS m/z (%): 238 (M+, 61), 223
(33), 195 (81), 181 (100), 179 (21), 165 (29). Anal. calcd.
for C18H22: C 90.70, H 9.30; found: C 90.82, H 9.18.
5,9-Di-i-propyl-1,2,3,4,4a,12b-hexahydro-1,4-
methanotriphenylene (10, R = i-Pr)
1H NMR δ: 7.29–7.24 (1H, m, H8), 7.23–7.17 (3H, m,
H10, H6, H7), 7.14 (1H, t, J = 7.5 Hz, H11), 7.03 (1H, d
further split, J = 7.3 Hz, H12), 3.76 (1H, hept., J = 6.8 Hz,
CH(C9)), 3.34 (1H, d, J = 9.4 Hz, H12b), 3.20 (1H, hept.,
J = 6.8 Hz, CH(C5)), 3.06 (1H, d, J = 9.4 Hz, H4a), 2.30
(1H, m, H4), 2.21 (1H, m, H1), 1.81–1.56 (4H, m, H2 exo,
H3 exo, H2 endo, H3 endo), 1.53 (3H, d, J = 6.8 Hz,
CH3CH(C9)), 1.36 (3H, d, J = 6.8 Hz, CH3CH(C5)), 1.24–
1.17 (4H, m, H13 syn, CH3CH(C5) centred at 1.21), 1.06
(3H, d, J = 6.8 Hz, CH3CH(C9)), 0.96 (1H, d quintets, J =
10.0, 1.5 Hz, H13 anti). 13C NMR δ: 147.45, 145.26, 140.04,
135.73, 133.94, 132.69, 126.99 (C8), 126.67 (C11), 125.64
(C7*), 125.19 (C12), 124.87 (C10), 124.27 (C6*), 48.57
(C1), 47.63 (C4, C12b), 42.82 (C4a), 33.77 (C13), 32.10
(C3), 30.52 (CH(C9)), 28.64 (CH(C5)), 28.28 (C2), 26.71
(CH3CH(C9)), 24.65 (CH3CH(C5)), 24.03 (CH3CH(C9)),
5-Methoxycarbonyl-1,2,3,4,4a,8b-hexahydro-1,4-
methanobiphenylene (8, R = CO2Me)
1H NMR δ: 7.78 (1H, dd, J = 7.8 Hz), 7.27 (1H, dd, J =
7.8, 7.4 Hz), 7.15 (1H, d, J = 7.4 Hz), 3.39 (1H, d, J =
3.7 Hz), 3.20 (1H, d, J = 3.8 Hz), 2.48–2.43 (1H, m), 2.31–
2.25 (1H, m), 1.65–1.55 (2H, m), 1.29–1.18 (1H, m), 0.97
(1H, d quintets, J = 10.2, 1.4 Hz), 0.78 (1H, d quintets, J =
10.2, 1.7 Hz). MS m/z (%): 228 (M+, 7), 187 (100), 155
(89), 141 (26), 128 (38), 115 (22).
5,9-Dimethoxycarbonyl-1,2,3,4,4a,12b-hexahydro-1,4-
methanotriphenylene (10, R = CO2Me)
Mp (hexane–CH2Cl2, 1:1) 142 to 143 °C. IR (KBr) ν:
1
1735, 1712. H NMR δ: 7.71 (1H, dd, J = 7.8, 1.2 Hz, H6),
7.42 (1H, dd, J = 7.5, 1.5 Hz, H10), 7.37–7.31 (2H, m, H8,
H12), 7.25 (1H, t, J = 7.5 Hz, H11), 7.17 (1H, t, J = 7.8 Hz,
© 2005 NRC Canada

746
Can. J. Chem. Vol. 83, 2005
H7), 3.92 (3H, s, CH3O2C(C5)), 3.90 (1H, d, J = 9.9 Hz,
H4a), 3.76 (3H, s, CH3O2C(C9)), 3.30 (1H, d, J = 9.9 Hz,
H12b), 2.29 (1H, br s, H4), 2.26 (1H, br s, H1), 1.79–1.55
(4H, m, H2 exo, H3 exo, H2 endo, H3 endo), 1.29 (1H, d
quintets, J = 10.2, 1.8 Hz, H13 syn), 1.02 (1H, d quintets,
J = 10.2, 1.2 Hz, H13 anti). 13C NMR δ: 172.13 (CO),
168.77 (CO), 140.48 (q), 139.47 (q), 132.27 (q), 132.14 (q),
131.42 (C12), 131.17 (C8), 130.96 (q), 130.32 (C6), 129.92
(q), 128.15 (C10), 127.32 (C11), 125.29 (C7), 52.30
(CH3CO2(C9)), 52.14 (CH3CO2(C5)), 49.45 (C4), 49.12
(C1), 46.60 (C12b), 42.76 (C4a), 33.57 (C13), 31.15 (C2*),
29.25 (C3*). MS m/z (%): 362 (M+, 29), 295 (29), 294
(100), 293 (22), 263 (72), 204 (15), 203 (17), 176 (18).
Anal. calcd. for C23H22O4: C 76.22, H 6.12; found: C 76.02,
H 6.07.
Acknowledgments
We gratefully acknowledge the financial support by the
University of Parma and Ministero dell’Università e della
Ricerca Scientifica
e
Tecnologica (MIUR, project
No. 2003039774). Mass and NMR facilities were provided
by Centro Interfacoltà di Misure dell’Università di Parma.
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