trans-2,2′-Bi(1-phenyladamantylidene): The most twisted biadamantylidene

Article abstract of DOI:10.1021/jo020247+

The Grignard coupling of 2,2-dibromo-1-phenyladamantane gave trans-2,2′-bi(1-phenyladamantylidene) (1-Ph). Single-crystal X-ray analysis indicated that 1-Ph has a 23.2° twisted double bond, which is much more distorted than that of parent 2,2′-biadamantylidene (1-H) and that of the ethyl-substituted derivative (1-Et). A cyclic voltammogram showed a reversible electron oxidation wave at 0.87 V vs Fc/Fc⁺, which is 0.19 V lower than 1-H, indicating a significant increase in the HOMO energy level due to the distortion. The reaction of 1-Ph with 0.9 equiv of bromine gave an intramolecular Friedel-Crafts alkylation product, while bromination of 1-H and 1-Me has been reported to give a bridged bromonium ion and a rearranged product, 2-(1-methyl-2-adamantylidene)-4-bromotricyclo [5,3,1,0^3.9]undec-4-ene, respectively.

Full text of DOI:10.1021/jo020247+

tr a n s-2,2′-Bi(1-p h en yla d a m a n tylid en e): Th e Most Tw isted
Bia d a m a n tylid en e
Takao Okazaki,* Kohei Ogawa, Toshikazu Kitagawa, and Ken’ichi Takeuchi
Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University,
Sakyo-ku, Kyoto 606-8501, J apan
okazaki@scl.kyoto-u.ac.jp
Received April 8, 2002
The Grignard coupling of 2,2-dibromo-1-phenyladamantane gave trans-2,2′-bi(1-phenyladaman-
tylidene) (1-P h ). Single-crystal X-ray analysis indicated that 1-P h has a 23.2° twisted double bond,
which is much more distorted than that of parent 2,2′-biadamantylidene (1-H) and that of the
ethyl-substituted derivative (1-Et). A cyclic voltammogram showed a reversible electron oxidation
wave at 0.87 V vs Fc/Fc+, which is 0.19 V lower than 1-H, indicating a significant increase in the
HOMO energy level due to the distortion. The reaction of 1-P h with 0.9 equiv of bromine gave an
intramolecular Friedel-Crafts alkylation product, while bromination of 1-H and 1-Me has been
reported to give a bridged bromonium ion and a rearranged product, 2-(1-methyl-2-adamantylidene)-
4-bromotricyclo[5,3,1,03.9]undec-4-ene, respectively.
SCHEME 1
In tr od u ction
2,2′-Biadamantylidene (1-H) is the first olefin to be
isolated as a stable bridged bromonium salt 2-H, which
is known as the intermediate of bromination.1 The
success is attributed to its characteristic structure in
which the double bond is protected by robust adamantyl
frameworks to prevent normal 1,2-addition. Reactions
with chlorine,2 nitronium,2b,3 nitrosonium,2b,3 benzene-
sulfenyl chloride,4 and benzeneselenenyl chloride5 have
been investigated, and the bridged species were consid-
ered as reaction intermediates. In addition, the central
double bond of 1-H is forced to twist by the introduction
of substituents at adjacent positions. Lenoir et al. re-
ported the synthesis of trans-dimethyl- and trans-diethyl-
substituted 2,2′-biadamantylidenes (1-Me and 1-Et, re-
spectively) with twisted double bonds by the McMurry
coupling.6 They indicated that the double bond becomes
more distorted with increasing bulkiness of the substit-
uents and that 1-Et has a twist angle of 12.3°, as
determined by X-ray single-crystal analysis. Recently,
bromination of 1-Me was reported to give bromide 3 via
a bridged bromonium ion 2-Me, although this ion was
not sufficiently stable to be isolated.7
Introduction of a substituent bulkier than an ethyl
group to 1-H is expected to twist the double bond further,
which can lead to different reaction behavior. The free-
energy difference between the equatorial and axial
conformers of phenylcyclohexane is estimated to be about
1 kcal/mol larger than that for ethylcyclohexane (Scheme
1).8 Therefore, the phenyl derivative, trans-2,2′-bi(1-
phenyladamantylidene) (1-P h ), is expected to be more
distorted at the double bond. We now report the synthesis
and reaction behavior of 1-P h . The molecular structure,
in particular the twist angles of double bonds, was
determined by single-crystal X-ray analysis. Oxidation
potentials of 1-P h were measured by cyclic voltammetry,
and its electrophilic reaction with bromine was investi-
* Corresponding author. Phone: +81-75-753-5714. Fax: +81-75-
753-3350.
(1) Strating, J .; Wieringa, J . H.; Wynberg, H. J . Chem. Soc., Chem.
Commun. 1969, 907. For reviews, see: Brown, R. S. Acc. Chem. Res.
1997, 30, 131.
(2) (a) Wieringa, J . H.; Strating, J .; Wynberg, H. Tetrahedron Lett.
1970, 4579. (b) Olah, G. A.; Schilling, P.; Westerman, P. W.; Lin, H.
C. J . Am. Chem. Soc. 1974, 96, 3581.
(3) Nelsen, S. F.; Akaba, R. J . Am. Chem. Soc. 1981, 103, 2096.
(4) Huang, X.; Batchelor, R. J .; Einstein, F. W. B.; Bennet, A. J . J .
Org. Chem. 1994, 59, 7108.
(5) Garratt, D. G. Tetrahedron Lett. 1978, 1915.
(6) (a) Lenoir, D.; Dauner, H.; Frank, R. M. Chem. Ber. 1980, 113,
2636. (b) Lenoir, D.; Frank, R. M.; Cordt, F.; Gieren, A.; Lamm, V.
Chem. Ber. 1980, 113, 739. (c) Cordt, F.; Frank, R. M.; Lenoir, D.
Tetrahedron Lett. 1979, 505. (d) Lenoir, D.; Frank, R. Tetrahedron Lett.
1978, 53.
(7) Chiappe, C.; De Rubertis, A.; Lemmen, P.; Lenoir, D. J . Org.
Chem. 2000, 65, 1273.
(8) The ∆G° values for ethylcyclohexane and phenylcyclohexane are
1.79 and 2.8 kcal/mol, respectively: Eliel, E. L.; Wilen, S. H.; Mander,
L. N. Stereochemistry of Organic Compounds; Wiley & Sons: New
York, 1994; p 697.
10.1021/jo020247+ CCC: $22.00 © 2002 American Chemical Society
Published on Web 07/30/2002
J . Org. Chem. 2002, 67, 5981-5986
5981

Okazaki et al.
TABLE 1. Selected Bon d Len gth s, Bon d An gles, a n d Tor sion An gles for 1-P h Deter m in ed by X-r a y Cr ysta llogr a p h ic
An a lysis
bond length, Å
C(2)-C(2′)
C(1)-C(2)
C(2)-C(3)
C(1)-C(11)
bond angle, deg
C(1)-C(2)-C(2′)
C(3)-C(2)-C(2′)
C(1)-C(2)-C(3)
C(2)-C(1)-C(11)
C(8)-C(1)-C(11)
C(9)-C(1)-C(11)
torsion angle, deg
C(1)-C(2)-C(2′)-C(1)
C(1)-C(2)-C(2′)-C(3′)
C(3)-C(2)-C(2′)-C(3′)
C(3)-C(2)-C(2′)-C(1′)
1.351(4)
1.548(3)
1.538(3)
1.529(3)
127.1(3)
123.0(3)
109.2(2)
116.0(2)
112.6(2)
104.4(2)
167.2(3)
-23.2(2)
146.3(4)
-23.2(2)
SCHEME 2
gated. The results are compared with those for the parent
alkene and other substituted 2,2′-biadamantylidenes.
Resu lts a n d Discu ssion
Syn th esis. The synthetic method for trans-2,2′-bi(1-
phenyladamantylidene) (1-P h ) is shown in Scheme 2. The
J ones oxidation9 of a mixture of exo- and endo-4-phenyl-
4-protoadamantanols (4)10-12 yielded 1-phenyl-2-adaman-
tanone (5). Then, ketone 5 was converted to 2,2-dibromo-
1-phenyladamantane (6) by treatment with a mixture of
PBr3 and PBr5.13,14 Subsequent reductive coupling of 6
with magnesium produced the desired olefin 1-P h , which
contained a small amount of unknown hydrocarbons.
Following preparative recycling GPC and repeated re-
crystallization, pure 1-P h was obtained as colorless
crystals in 14% yield.
F IGURE 1. ORTEP drawing for the molecular structure of
1-P h determined by single-crystal X-ray diffraction analysis.
SCHEME 3
13C NMR measurements showed six aliphatic and five
aromatic and olefinic signals, and the quarternary C(2)/
C(2′) resonance appeared at δ 152.8. The H(3) proton
signal appeared at δ 2.17, the assignment of which is
based on the HETCOR measurement. This proton is
largely shielded compared to the corresponding proton
in 1-H (δ 2.90).
In preliminary studies, we attempted the modified
McMurry coupling of 5, which is generally useful for the
preparation of a symmetric olefin from a ketone,15,16 but
the reduction of 5 using a low-valence titanium reagent
(TiCl4/Zn) resulted in quantitative formation of undesired
1-phenyl-2-adamantanol,10,17 presumably due to difficulty
of association due to steric hindrance.
Twist angles, out-of-plane bendings,24 and bond lengths
of the double bonds shown in Scheme 3 are summarized
in Table 2. The central π-bond has a twist angle (θ) of
23.2°, showing marked distortion due to the steric repul-
sion between a phenyl substituent and the adamantyl
group on the opposite side. The twist angle is larger than
that reported for 1-H (0.0°) 18 and that for 1-Et (12.3°).6b
The central double bond (1.351 Å) is elongated in
comparison with that of 1-H (1.336 Å) and is as long as
that for 1-Et (1.358 Å). Other noticeable distortions can
be seen at bending angles around C(1) and C(2) carbons.
The bond angle of C(2)-C(1)-C(11) is larger than those
of C(8)-C(1)-C(11) and C(9)-C(1)-C(11), and the angle
of C(1)-C(2)-C(2′) is also larger than that of C(3)-C(2)-
C(2′) by 4°. The olefinic C(2) carbon is considerably
pyramidalized with an out-of-plane angle of 10.5°. More-
over, C(1)-C(9) and C(3)-C(10) (1.557, 1.554 Å) are
slightly longer than C(1)-C(8) and C(3)-C(4) (1.547,
1.534 Å), respectively, which is also indicative of the
distortion of the adamantyl framework. The torsion
angles around the double bond indicate that the olefin
has a twisted/syn-folded conformation.19
Molecu la r Str u ctu r e. The molecular structure of
1-P h obtained by X-ray crystallographic analysis is
depicted in Figure 1. Selected bond distances, bond
angles, and torsion angles are summarized in Table 1.
(9) Raber, D. J .; J anks, C. M. J . Org. Chem. 1983, 48, 1101.
(10) Lenoir, D. Chem. Ber. 1973, 106, 78.
(11) Chakrabarti, J . K.; Hotten, T. M.; Rackham, D. M.; Tupper, D.
E. J . Chem. Soc., Perkin Trans. 1 1976, 1893.
(12) Tseng, C. C.; Handa, I.; Abdel-Sayed, A. N.; Bauer, L. Tetra-
hedron 1988, 44, 1893.
(13) Geluk, H. W. Synthesis 1970, 652.
(14) Bartlett, P. D.; Ho, M. S. J . Am. Chem. Soc. 1974, 96, 627.
(15) Fleming, M. P.; McMurry, J . E. Organic Syntheses; Wiley: New
York, 1990; Collect. Vol. VII, p 1.
(16) Tolstikov, G. A.; Lerman, B. M.; Belogaeva, T. A. Synth.
Commun. 1991, 21, 877.
(17) Lenoir, D.; Burghard, H. J . Chem. Res. (S) 1980, 396.
(18) Swen-Walstra, S. C.; Visser, G. J . J . Chem. Soc. D. 1971, 82.
(19) Biedermann, P. U.; Stezowski, J . J .; Agranat, I. Eur. J . Org.
Chem. 2001, 15.
5982 J . Org. Chem., Vol. 67, No. 17, 2002

trans-2,2′-Bi(1-phenyladamantylidene)
F IGURE 2. Raman spectra for 1-H (a), 1-P h (b), and 5 (c). An asterisk (*) denotes observed signals by IR spectroscopy.
TABLE 2. Tw ist An gles (θ), Ou t-of-P la n e Ben d in gs (O),
a n d Bon d Len gth s of th e C(2)dC(2′) π-Bon d for 1-H, 1-Et,
a n d 1-P h Obta in ed by MM3, P M3, HF , a n d BLYP
Ca lcu la tion s In clu d in g th e Resu lts of X-r a y Diffr a ction
An a lysis
TABLE 3. Str etch in g F r equ en cy for Dou ble Bon d by
Ra m a n Sp ectr oscop y a n d HF /6-31G(d ) Ca lcu la tion s
olefin
raman, cm-1
HF/6-31G(d), cm-1 a
1-H
1658b
1592b
1572b
1590
1683
1620
1599
1617
1-Me
1-Et
1-P h
twist angle out-of-plane
for π-bond
bendings
(φ), deg
C(2)dC(2′)
bond length, Å
olefin
theory
X-ray
MM3
PM3
RHF/6-31G(d)
BLYP/6-31G(d)
(θ), deg
a
b
Values after scale factor correction. From ref 6.
1-H
0.0a
0.0
0.0
0.0
0.0
0.0a
0.0
0.0
0.0
0.0
1.336a
1.356
1.341
1.332
1.361
1.358b
1.362
1.354
1.348
1.377
1.351
1.364
1.352
1.343
1.372
literature data reported by Lenoir.6 The spectrum for
1-P h showed five peaks, among which two peaks, 1590
and 1429 cm-1, were found to be IR inactive by IR
spectroscopy. The other three signals, which can be
attributed to phenyl ring stretchings and CH2 scissoring
vibrations, have frequencies similar to those for 5. HF/
6-31G(d)//HF/6-31G(d) frequency calculations indicate
that the CdC stretching has a frequency of 1617 cm-1
with Raman activity and small IR activity and that the
signal 1429 cm-1 should be CH2 scissoring vibration.
Therefore, the IR inactive 1590 cm-1 signal is assigned
to the CdC stretching vibration. This stretching fre-
1-Et X-ray
MM3
12.3b
38.7
34.2
11.8
25.0
23.2
24.1
26.3
21.7
21.4
8.9b
15.4
10.9
5.4
PM3
RHF/6-31G(d)
BLYP/6-31G(d)
1-P h X-ray
6.3
10.5
14.5
13.6
6.4
MM3
PM3
RHF/6-31G(d)
BLYP/6-31G(d)
7.3
a
b
Ref 18. Ref 6b.
quency is 68 cm-1 smaller than that of 1-H, 1658 cm-1
,
and similar to that of 1-Et, 1572 cm-1 (Table 3). This
observation suggests that the bond strength in 1-P h is
not weakened significantly compared with that of 1-Et,
though 1-P h is more twisted than 1-Et.
The distance between H(3) and the ipso carbon of a
benzene ring, C(11′), is measured to be only 2.37 Å,
whereas the sum of the van der Waals radius of hydrogen
(1.2 Å) and the thickness of the π-electron cloud (1.7 Å)
of a phenyl substituent is 2.9 Å.20 The close proximity
accounts for the 0.73 ppm shielding for H(3) observed in
Cyclic Volta m m etr y. The redox behavior of 1-P h was
examined by cyclic voltammetry in acetonitrile (Figure
3). A reversible oxidation wave was observed at 0.87 V
vs Fc/Fc+ (E1/2), which is lower by 0.19 V than the E1/2 of
1-H (1.06 V vs Fc/Fc+).25 Differential pulse voltammetric
measurements (DPV) also gave essentially the same
oxidation potentials. The decrease in the oxidation po-
tential suggests an increase in the HOMO energy level
due to a loss of the overlap of p-orbitals by twisting, which
is corroborated by theoretical calculations. HF/6-31G(d)
calculations show a rise in the HOMO energy level from
-8.41 eV for 1-H to -8.11 eV for 1-P h .
1
the H NMR spectrum (see above).21
The structures for 1-H, 1-Et, and 1-P h were computed
with the MM3,22 PM3,23 HF, and DFT methods. Selected
data are summarized in Table 2. All the optimized
structures are symmetrical. MM3 and PM3 methods have
a tendency to overestimate bending and twisting distor-
tions. The twist angles and bond lengths calculated by
HF/6-31G(d) are closer to those determined by X-ray
analysis than those determined by BLYP/6-31G(d). There-
fore, HF/6-31G(d) calculation data are used for the
following discussion.
Ra m a n Sp ectr oscop y. Vibrations of the central
double bonds are inactive in IR spectroscopy but active
in Raman due to the symmetrical structural form of
1-P h . Observed Raman spectra are shown in Figure 2.
The obtained spectrum for 1-H is in agreement with the
Reaction s with Br om in e an d Tr iflu or oacetic Acid.
Dropwise addition of 0.9 equiv of bromine to 1-P h in
dichloromethane at room temperature led to clean forma-
(23) MOPAC, version 6: Stewart, J . J . P. QCPE Bull. 1989, 9, 10.
Revised as version 6.01 for UNIX machine: Hirano, T. J CPE Newslet-
ter 1989, 1, 10.
(24) Okazaki, T.; Tokunaga, K.; Kitagawa, T.; Takeuchi, K. Bull.
Chem. Soc. J pn. 1999, 72, 549.
(20) Bott, G.; Field, L. D.; Sternhell, S. J . Am. Chem. Soc. 1980,
102, 5618.
(21) Ernst, L. Prog. NMR Spectrosc. 2000, 37, 47.
(22) Allinger, N. L. Molecular Mechanics. Operating Instructions for
the MM3 Program, 1989 Force Field (for IBM RS/6000); Technical
Utilization Corporation: Powell, OH, 1992.
(25) (a) The observed E1/2 of 1-H (1.06 V vs Fc/Fc+ ) 1.43 V vs SCE)
is close to reported values of 1.43 V in 7:3 acetonitrile-dichloromethane
and 1.45 V vs SCE in acetonitrile (refs 25b and 26, respectively). The
E1/2 vs SCE was calculated by an equation of E1/2 (vs Fc/Fc+) + 0.374
V vs SCE taken from ref 25b. (b) Komatsu, K.; Kamo, H.; Tsuji, R.;
Takeuchi, K. J . Org. Chem. 1993, 58, 3219.
J . Org. Chem, Vol. 67, No. 17, 2002 5983

Okazaki et al.
F IGURE 4. ORTEP drawing for the structure of 7 determined
by single-crystal X-ray diffraction analysis (proton labeled as
m-CH is exceptionally deshielded in NMR).
F IGURE 3. Cyclic voltammogram (CV) and differential pulse
voltammogram (DPV) for 1-H (a and b) and 1-P h (c and d) in
acetonitrile containing 0.1 M n-Bu4NClO4. An asterisk (/)
denotes peaks for impurities.
1
Direct observation of the reaction solution by H NMR
analysis showed the clean formation of 7 in 5 min at room
temperature. Similar acid-catalyzed Friedel-Crafts reac-
tion was reported by Mitchell and Zhang28 for dehydro-
pyrene derivatives. The NMR spectra showed no indica-
tion of the formation of diastereomer 9. PM3 calculations
indicated that compound 7 is more stable than isomer 9
by 6 kcal/mol.
SCHEME 4
tion of hydrocarbon 7 (Scheme 4). On addition of the
initial portions of bromine, the color immediately disap-
peared, but it persisted thereafter. The mass spectrum
(FAB+, NPOE) of 7 shows m/e 421 (M+ + H) and 420
(M+) signals as a hydrocarbon C32H36 and that there are
no isotope peaks due to the presence of bromine. A single
crystal was analyzed by the X-ray diffraction method,
which revealed the structure of 7 as shown in Figure 4.
NMR and elemental analytical data are in agreement
with the above structure. A doublet peak that was
assigned to m-CH (Figure 4) was observed at a lower
field, δ 8.19, than other aromatic signals. The exception-
ally large deshielding is attributed to the influence of the
ring current of the adjacent phenyl substituent.21
A possible mechanism for the formation of 7 is shown
in Scheme 5. Initially, bromine attacks the central double
bond to produce a bridged bromonium ion or the corre-
sponding open cation. Then the formation of a C-C bond
and subsequent loss of a proton gives bromide 8. Once a
small amount of proton is formed, acid-catalyzed in-
tramolecular Friedel-Crafts alkylation converts the rest
of 1-P h to 7.27 This mechanism is supported by the fact
that treatment of 1-P h with trifluoroacetic acid in
chloroform yielded the same product 7 quantitatively.
When bromination was carried out using excess bro-
mine under similar conditions, a brominated compound
10 was obtained (Scheme 4). The NMR spectra of 10 are
very similar to 7 except for signals in the aromatic region.
One aromatic CH carbon disappeared, and a remarkably
shielded aromatic quarternary carbon (at δ 118.5) was
observed instead. The multiplicity of the most deshielded
(δ 8.19) aromatic proton signal in 7, which was assigned
to m-CH (Figure 4), was changed to a singlet (δ 8.31).
These findings suggest that bromination occurred at the
carbon next to m-CH.
The reaction with a stronger acid, CF3SO3H, gave a
mixture of products with no clearly distinguishable NMR
signals.
Con clu sion s
A highly congested olefin, 1-P h , was synthesized by
Grignard coupling of a geminal dibromide. This method
is supposed to be effective for the synthesis of highly
congested olefins that are difficult to synthesize by
McMurry coupling. X-ray single-crystal analysis indi-
cated that the double bond is twisted by 23.2°, which is
(26) (a) Nelsen, S. F. Acc. Chem. Res. 1987, 20, 269. (b) Nelsen, S.
F.; Kessel, C. R. J . Am. Chem. Soc. 1979, 101, 2503.
(27) Fuson, R. C. Reactions of Organic Compounds; Wiley: New
York, 1962; p 128.
(28) Mitchell, R. H.; Zhang, L. J . Org. Chem. 1999, 64, 7140.
5984 J . Org. Chem., Vol. 67, No. 17, 2002

trans-2,2′-Bi(1-phenyladamantylidene)
SCHEME 5
IR (KBr, cm-1) 2904, 1494, 1442, 753, and 699; 1H NMR (400
MHz, CDCl3) δ 1.69-1.88 (m, 6H), 2.16 (brs, 2H), 2.71-2.81
(m, 3H), 3.10 (d, J ) 11.7 Hz, 2H), 7.27-7.38 (m, 3H), 7.63
(dd, J ) 8.3, 1.5 Hz, 2H); 13C NMR (100 MHz, CDCl3) δ 28.0
(2CH), 35.3 (2CH2), 37.8 (CH2), 39.3 (2CH2), 48.4 (C), 49.5 (CH),
91.7 (C), 126.8 (2CH), 127.1 (CH), 128.4 (2CH), 143.8 (C). Anal.
Calcd for C16H18Br2: C, 51.92; H, 4.90. Found: C, 51.77; H,
4.85.
the most twisted double bond among those of known 2,2′-
biadamantylidenes. 1-P h underwent anodic oxidation to
give a radical cation more easily than 1-H with a normal
planar double bond. The radical cation is sufficiently
stable to show a reversible oxidation wave, but the
cationic intermediate in the electrophilic reaction with
bromine and trifluoroacetic acid is unstable, giving 7 at
room temperature. The enhanced reactivity is consistent
with the observation by Chiappe et al.7 that the bridged
bromonium ion from 1-Me with a twisted double bond is
more reactive than that from 1-H.
tr a n s-2,2′-Bi(1-p h en yla d a m a n tylid en e) (1-P h ). A solu-
tion of 6 (500 mg, 1.4 mmol) in dry ether (42 mL) with
magnesium (0.7 g, 29 mmol) was heated to reflux under N2.
Then, 1,2-dibromoethane (2.5 mL, 29 mmol) was added drop-
wise over a period of 2 h. After the solution had been refluxed
with stirring for an additional 15 h, water was carefully added.
The resulting mixture was extracted with ether and CHCl3.
The combined organic layers were washed with saturated NaCl
and dried (MgSO4). Removal of the solvent afforded a pale
yellow oil, which upon recycle HPLC and recrystallization
three times from hexane and once from CHCl3 gave pure trans-
2,2′-bi(1-phenyladamantylidene) (1-P h ) as colorless crystals
(41 mg, 14%): mp 278.5-280.0 °C; IR (KBr, cm-1) 2912, 1599,
Exp er im en ta l Section
Melting points are uncorrected. NMR spectra were recorded
on 400 and 270 MHz instruments. IR was obtained by using
FT-IR spectrophotometer. Raman experiments were performed
on powdered samples. FAB mass spectra were obtained using
o-nitrophenyl octyl ether as a matrix in the positive mode.
Elemental analyses were performed by the Microanalytical
Center, Kyoto University, Kyoto. 2,2′-Biadamantylidene (1-
H)15 and exo- and endo-4-phenyl-4-protoadamantanol (4)10-12
were prepared by literature procedures. Tetra-n-butylammo-
nium perchlorate was recrystallized from 5:1 AcOEt-hexane.
Anhydrous solvents for syntheses were purified by standard
procedures. Other commercially available reagents were of
reagent-grade quality and used as received. Medium-pressure
liquid chromatography (MPLC) was conducted on silica gel
(45-75 µm). Recycle preparative HPLC was performed with
GPC columns (φ 20 mm × 600 mm) using CHCl3 as an eluent.
1-P h en yl-2-a d a m a n ta n on e (5). To a solution of exo- and
endo-4-phenyl-4-protoadamantanol (4, 8.5 g, 37 mmol) in
acetone (1.0 L) was added dropwise a solution of CrO3 (15 g,
150 mmol) in H2SO4 (12.4 mL). After being stirred for 24 h,
the mixture was filtered, and most of the solvent was evapo-
rated. The resulting mixture was diluted with water and
extracted by ether, and the ether solution was dried (MgSO4).
Removal of the solvent afforded brown crystals, recrystalliza-
tion of which from hexane gave 1-phenyl-2-adamantanone (5)
as colorless crystals (3.4 g) in 41% yield: mp 140.0-140.5 °C;
IR (KBr, cm-1) 2900, 1712, 1444, 1064, 742, and 695; 1H NMR
(270 MHz, CDCl3) δ 1.91 (m, 1H), 2.00 (m, 1H), 2.11-2.30 (m,
8H), 2.44 (m, 2H), 2.73 (brs, 1H), 7.22-7.29 (m, 3H), 7.36 (m,
2H); 13C NMR (67.8 MHz, CDCl3) δ 28.3 (2CH), 35.6 (CH2),
39.2 (2CH2), 45.0 (2CH2), 47.4 (CH), 53.9 (C), 126.6 (CH), 126.9
(2CH), 127.9 (2CH), 142.4 (C), 215.2 (C). Anal. Calcd for
1
1492, 1442, 752, and 698; H NMR (CDCl3, 270 MHz) δ 1.31
(dd, J ) 12.0, 2.7 Hz, 4H), 1.45 (d, J ) 12.2 Hz, 4H), 1.60 (s,
4H), 1.85 (d, J ) 11.7 Hz, 4H), 1.94 (brs, 4H), 2.08 (d, J ) 2.7
Hz, 4H), 2.17 (t, J ) 2.4 Hz, 2H), 7.14 (dd, J ) 7.3, 7.3 Hz,
2H), 7.33 (dd, J ) 7.6, 7.6 Hz, 4H), 7.44 (dd, J ) 7.3, 7.3 Hz,
4H); 13C NMR (CDCl3, 75.5 MHz) δ 28.6 (4CH), 36.3 (2CH2),
36.7 (2CH), 38.2 (4CH2), 44.9 (2C), 46.0 (4CH2), 124.7 (2C),
125.1 (4CH), 128.1 (4CH), 140.0 (2C), 152.8 (2C). Anal. Calcd
for C32H36: C, 91.37; H, 8.63. Found: C, 90.77; H, 8.82.
Rea ction of tr a n s-2,2′-Bi(1-p h en yla d a m a n tylid en e) (1-
P h ) w ith Br om in e. To a solution of 1-P h (120 mg, 0.30 mmol)
in CH2Cl2 (9.5 mL) was added dropwise 3.2 × 10-2 M bromine
in CH2Cl2 (0.8 mL) in the dark. After the solution had been
stirred overnight, the solvent was evaporated to give a pale
yellow oil, which was analyzed by NMR to show almost
quantitative formation of 7. HPLC with GPC columns and
recrystallization from hexane gave pure 7 (51 mg, 41%) as
colorless prisms, which were used for X-ray crystallographic
analysis: mp 206.5-207.0 °C (from hexane); IR (KBr, cm-1
)
2898, 2848, 1596, 1496, 1468, 1447, 750, and 697; 1H NMR
(270 MHz, CDCl3) δ 0.99 (d, J ) 11.2 Hz, 1H), 1.47 (d, J ) 7.9
Hz, 2H), 1.58 (brs, 1H), 1.80 (m, 14H), 2.14 (s, 1H), 2.30 (d, J
) 12.5 Hz, 3H), 2.53 (d, J ) 13.2 Hz, 1H), 2.89 (brs + d, J )
15.5 Hz, 2H), 3.00 (d, J ) 12.5 Hz, 1 H), 3.51 (d, J ) 13.5 Hz,
1H), 6.89 (dd, J ) 7.3, 1.3 Hz, 2H), 6.96 (brs, 2H), 7.14 (d, J )
7.3 Hz, 2H), 7.20 (m, 2H), 8.19 (d, J ) 7.9 Hz, 1H); 13C NMR
(75.5 MHz, CDCl3) δ 28.2 (CH), 28.4 (CH), 29.0 (CH), 29.1
(CH), 33.3 (CH2), 33.7 (CH2), 34.2 (CH2), 34.4 (CH), 35.9 (CH),
36.9 (CH2), 39.6 (CH2), 39.9 (CH2), 40.4 (CH2), 41.4 (CH2), 43.5
(CH2), 43.7 (C), 44.4 (CH2), 45.7 (C), 54.1 (CH), 60.6 (C), 121.2
(CH), 124.9 (CH), 125.3 (CH), 126.4 (CH), 126.9 (2CH), 127.6
(2CH), 130.5 (CH), 146.8 (C), 147.8 (C), 153.4 (C). Anal. Calcd
for C32H36: C, 91.37; H, 8.63. Found: C, 91.21; H, 8.65.
C
16H18O: C, 84.91; H, 8.02. Found: C, 84.77; H, 8.05.
2,2-Dibr om o-1-p h en yla d a m a n ta n e (6). To a solution of
5 (1.50 g, 6.6 mmol) in PBr3 (23 mL) was added PBr5 (4.9 g,
11 mmol) in small portions over a period of 1.5 h. After being
stirred for 24 h, the reaction mixture was diluted with ice-
water and extracted with ether. The extract was washed with
saturated NaHCO3 and water and dried (MgSO4). Evaporation
of the solvent afforded a pale yellow oil, recrystallization of
which from hexane gave 2,2-dibromo-1-phenyladamantane (6)
(1.4 g) as colorless crystals in 55% yield: mp 172.5-173.5 °C;
Reaction of 1-P h (5.0 mg, 0.012 mmol) in CH2Cl2 (2.0 mL)
with 0.65 M bromine in CH2Cl2 (0.17 mL) gave a mixture of
10 and several unknown compounds as a pale yellow oil. HPLC
J . Org. Chem, Vol. 67, No. 17, 2002 5985

Okazaki et al.
purification gave 10 as a major component (16% yield): pale
yellow oil; 1H NMR (270 MHz, CDCl3) δ 0.96 (d, J ) 11.2 Hz,
1H), 1.44 (d, J ) 7.9 Hz, 2H), 1.50-1.95 (m, 14H), 2.17 (s,
1H), 2.30 (m, 3H), 2.51 (d, J ) 13.2 Hz, 1H), 2.80 (d, J ) 15.5
Hz, 1H), 2.85 (brs, 1H), 2.98 (d, J ) 12.5 Hz, 1 H), 3.41 (d, J
) 13.5 Hz, 1H), 6.86 (d, J ) 7.3 Hz, 1H), 7.00 (brs, 2H), 7.20-
7.40 (m, 4H), 8.31 (s, 1H); 13C NMR (100 MHz, CDCl3) δ 28.0
(CH), 28.2 (CH), 28.8 (CH), 28.9 (CH), 33.1 (CH2), 33.5 (CH2),
34.0 (CH2), 34.3 (CH), 35.8 (CH), 36.8 (CH2), 39.5 (CH2), 39.7
(CH2), 40.1 (CH2), 41.2 (CH2), 43.2 (CH2), 43.5 (C), 44.3 (CH2),
45.6 (C), 54.1 (CH), 60.9 (C), 118.5 (C), 122.6 (CH), 125.5 (CH),
126.9 (2CH), 127.5 (2CH), 129.4 (CH), 133.2 (CH), 147.3 (C),
149.3 (C), 152.3 (C).
Rea ction of 1-P h w ith Tr iflu or oa cetic Acid . A solution
of 1-P h (1.7 mg, 4.0 × 10-3 mmol) in CDCl3 (0.45 mL)
containing CF3COOH (0.03 mL) was allowed to react at room
temperature overnight. The resulting mixture was analyzed
by NMR measurements, which indicated that only 7 had been
formed.
Ca lcu la tion s. Semiempirical PM3 results were obtained
with the MOPAC package.23 Empirical molecular mechanics
calculations were performed through the MM3(92)22 program.
HF and DFT calculations were performed using Gaussian 98
software.29 Geometry optimizations were verified by frequency
calculations (Tables of Cartesian coordinates, energies, and
number of imaginary frequencies are provided as Supporting
Information).
Sin gle-Cr yst a l X-r a y Cr yst a llogr a p h ic An a lysis of
1-P h a n d 7. Data were collected at room temperature. The
structure was solved by direct methods using SIR92 for 1-P h
and SHELXS-9730 for 7.
22.193(7) Å, c ) 10.763(8) Å, â ) 112.01(5)°, V ) 2274(2) Å3,
Z ) 4, dcalcd ) 1.228 g/cm3, λ (Mo KR) ) 0.71069 Å, µ ) 0.69
cm-1, R ) 0.049, Rw ) 0.049.
Cyclic Volta m m etr y. Cyclic voltammograms were ob-
tained with a system with a three-electrode cell composed of
a glassy carbon working electrode, a platinum wire counter
electrode, and a Ag/AgNO3 (0.01 M in CH3CN) reference
electrode. The observed potentials were corrected with refer-
ence to ferrocene added as an internal standard.
Ack n ow led gm en t. We thank Professor Yasuhiro
Awakura and Dr. Kuniaki Murase in Kyoto University
for Raman spectroscopy measurements.
Su p p or tin g In for m a tion Ava ila ble: Selected NMR spec-
tra for 1-P h , 7, and 10, calculated energies and Cartesian
coordinates for 1-H, 1-Et, and 1-P h optimized by HF and DFT
calculations, and results of X-ray analysis for 1-P h and 7. This
material is available free of charge via the Internet at
http://pubs.acs.org.
J O020247+
(29) Frisch, M. J .; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.;
Robb, M. A.; Cheeseman, J . R.; Zakrzewski, V. G.; Montgomery, J . A.,
J r.; Stratmann, R. E.; Burant, J . C.; Dapprich, S.; Millam, J . M.;
Daniels, A. D.; Kudin, K. N.; Strain, M. C.; Farkas, O.; Tomasi, J .;
Barone, V.; Cossi, M.; Cammi, R.; Mennucci, B.; Pomelli, C.; Adamo,
C.; Clifford, S.; Ochterski, J .; Petersson, G. A.; Ayala, P. Y.; Cui, Q.;
Morokuma, K.; Malick, D. K.; Rabuck, A. D.; Raghavachari, K.;
Foresman, J . B.; Cioslowski, J .; Ortiz, J . V.; Baboul, A. G.; Stefanov,
B. B.; Liu, G.; Liashenko, A.; Piskorz, P.; Komaromi, I.; Gomperts, R.;
Martin, R. L.; Fox, D. J .; Keith, T.; Al-Laham, M. A.; Peng, C. Y.;
Nanayakkara, A.; Challacombe, M.; Gill, P. M. W.; J ohnson, B. G.;
Chen, W.; Wong, M. W.; Andres, J . L.; Gonzalez, C.; Head-Gordon, M.;
Replogle, E. S.; Pople, J . A. Gaussian 98, revision A.9; Gaussian, Inc.:
Pittsburgh, PA, 1998.
1-P h : C32H36, MW ) 420.64. Crystal data: 0.20 × 0.20 ×
0.20 mm, monoclinic, space group C2/c, a ) 19.768(4) Å, b )
6.721(8) Å, c ) 18.437(5) Å, â ) 110.60(2)°, V ) 2292(2) Å3, Z
) 4, dcalcd ) 1.218 g/cm3, λ (Mo KR) ) 0.71069 Å, µ ) 0.68
cm-1, R ) 0.048, Rw ) 0.043.
(30) Sheldrick, G. M. SHELXS-97. Program for the Solution of
Crystal Structures; University of Gottingen: Gottingen, Germany,
1997.
7: C32H36, MW ) 420.64. Crystal data; 0.40 × 0.30 × 0.30
mm, monoclinic, space group P21/n, a ) 10.270(7) Å, b )
5986 J . Org. Chem., Vol. 67, No. 17, 2002