Medium-sized cyclophanes. Part 52: Synthesis and structures of [2.n] metacyclophane-1,2-diones

Article abstract of DOI:10.1039/b001145m

A series of syn- and anti-[2.n]metacyclophan-1-enes, 3, and [2.n]metacyclophane-1,2-diols, 4, were prepared in good yields by a McMurry cyclization of 1,n-bis(5-tert-butyl-3-formyl-2-methoxyphenyl)alkanes, 2. Upon increasing the length of the methylene bridge higher yields of 3 were obtained. The assignment of the syn and anti conformations has been confirmed by ¹H-NMR analyses. The 1,2-diol derivatives 4 were converted to the 1,2- diones 9 by Swern oxidation. However, [2.2]metacyclophane-1,2-dione, 9a, was found to be quite labile under treatment by silica gel column chromatography and on refluxing in toluene to give the dicarboxylic acid 10 in quantitative yield. Thus, a trapping reaction of diketone 9a was attempted, in which the crude diketone 9a was treated with o-phenylenediamine in ethanol at room temperature for 24 h to afford in almost quantitative yield the desired [2.2]metacyclophane 11 having a quinoxaline skeleton. Similarly, in the case of [2.3]- and [2.4]metacyclophanes, Swern oxidation of the trans-diols trans- 4b,c also afforded the desired diketones 9b,c in quantitative yields as stable yellow prisms.

Full text of DOI:10.1039/b001145m

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Medium-sized cyclophanes. Part 52:¤ synthesis and structures of
[2.n]metacyclophane-1,2-diones
Takehiko Yamato,*a Koji Fujita,a Ken-ichiro Okuyamaa and Hirohisa Tsuzukib
a Department of Applied Chemistry, Faculty of Science and Engineering, Saga University,
Honjo-machi 1, Saga-shi, Saga 840-8502, Japan. Fax: ]81 0952 28 8591;
E-mail: yamatot=cc.saga-u.ac.jp
b Center of Environmental Analysis, T ohwa Institute for Science, T ohwa University, 1-1-1
Chikushigaoka, Minami-ku, Fukuoka-shi, Fukuoka 815-8510, Japan
Received (in Montpellier, France) 25th August 1999; revised manuscript received and accepted 2nd February 2000
A series of syn- and anti-[2.n]metacyclophan-1-enes, 3, and [2.n]metacyclophane-1,2-diols, 4, were prepared in
good yields by a McMurry cyclization of 1,n-bis(5-tert-butyl-3-formyl-2-methoxyphenyl)alkanes, 2. Upon increasing
the length of the methylene bridge higher yields of 3 were obtained. The assignment of the syn and anti
conformations has been conÐrmed by 1H-NMR analyses. The 1,2-diol derivatives 4 were converted to the 1,2-
diones 9 by Swern oxidation. However, [2.2]metacyclophane-1,2-dione, 9a, was found to be quite labile under
treatment by silica gel column chromatography and on reÑuxing in toluene to give the dicarboxylic acid 10 in
quantitative yield. Thus, a trapping reaction of diketone 9a was attempted, in which the crude diketone 9a was
treated with o-phenylenediamine in ethanol at room temperature for 24 h to a†ord in almost quantitative yield the
desired [2.2]metacyclophane 11 having a quinoxaline skeleton. Similarly, in the case of [2.3]- and [2.4]metacyclo-
phanes, Swern oxidation of the trans-diols trans-4b,c also a†orded the desired diketones 9b,c in quantitative yields
as stable yellow prisms.
For many years various research groups have been attracted
by the chemistry and spectral properties of [2.2]MCP
([2.2]MCP \ [2.2]metacyclophane) skeleton.2,3 Its conforma-
tion, which was elucidated by X-ray measurements,4 is frozen
into a chair-like non-planar form. Many attempts have been
made to directly introduce functional groups into the methy-
lene groups of [2.2]MCPs, but these have failed because of the
deviation of the benzyl carbon atom from the plane of the
benzene ring.5
Singler and Cram have reported that bromination of
[2.2]paracyclophan-1-ene with bromine a†ords the corre-
sponding cis adduct.6 We have reported that di-tert-
butyldimethyl[2.n]MCP-1-enes were treated with an equi-
molar amount of benzyltrimethylammonium tribromide
On the other hand, in cyclophane chemistry, the reductive
coupling of carbonyl compounds by low-valent titanium, the
McMurry reaction,11 has been used before by Mitchell and
Weerawarna12 to synthesize cyclophanes with glycol units as
bridges. The McMurry reaction has also been used by Tanner
and Wennerstrom,13 and more recently by Hopf and
Mlynek14 and by Grutzmacher and Neumann15 to cyclize
suitable dialdehydes to yield unsaturated cyclophanes. Thus,
there is substantial interest in developing a more convenient
preparation of [2.n]MCP-1-enes or -1,2-diols than the con-
ventional sulfur method.7h9 We report here on the use of the
McMurry coupling reaction to prepare a series of [2.n]MCP-
1,2-diols with internal methoxy substituents and their conver-
sion to 1,2-diones by Swern oxidation.16
(BTMA Br ) in methylene dichloride to a†ord the cis adducts
3
to the bridged double bond.7h9 This result indicates the Ðrst
Results and discussion
success in the introduction of two bromo groups into the
methylene groups of dimethyl[2.n]MCPs. We have extended
the novel reaction mentioned above and reported on the ace-
tolysis of bromine adducts with silver acetate in acetic acid
and the conversion to dimethyl[2.n]MCP-1,2-diones via
hydrolysis followed by Swern oxidation of the dihydroxy
derivatives.10
The starting compounds, 1,n-bis(5-tert-butyl-2-methoxy-
phenyl)alkanes, 1, are easily prepared in three steps from
anisole by using the tert-butyl group as a positional protective
group on the aromatic ring.17 Formylation of 1 with dichloro-
methyl methyl ether in the presence of titanium tetrachloride
in methylene dichloride at room temperature for 2 h yields
1,n-bis(5-tert-butyl-3-formyl-2-methoxyphenyl)alkanes, 2, in
moderate yields (Scheme 1).
1,2-Bis(5-tert-butyl-3-formyl-2-methoxyphenyl)ethane, 2a,
was subjected to reductive coupling by the McMurry reaction
following GrutzmacherÏs procedure15 (Scheme 2, Table 1).
Although none of the desired [2.2]MCP-1-ene 3a was
observed, anti-[2.2]MCP-diol anti-4a was obtained in 18%
yield along with a small amount of the dimer 5 and 1,2-bis(5-
tert-butyl-2-methoxy-3-methylphenyl)ethane, 6a. The same
reaction in the presence of pyridine increased the yield of diol
anti-4a to 68% from 18%, but the formation of [2.2]MCP-1-
ene 3a was not observed. This Ðnding seems to be due to the
much more strained structure of 3a than diol 4a during the
However, we have not yet succeeded in preparing
[2.2]MCP-1,2-dione due to the novel transannular reaction
arising from the electronic interaction between two benzene
rings, the proximity of the 8,16-positions and the release of the
considerable strain energy to form the more stable annulene
p-electron system, 10b,10c-dihydropyrene. Thus, the reaction
of
5,13-di-tert-butyl-8,16-dimethyl[2.2]MCP-1-ene7
with
bromine a†ords 4,5,9,10-tetrabromo-2,7-di-tert-butyl-trans-
10b,10c-dimethyl-10b,10c-dihydropyrene in good yield, but
not the adduct to the bridged double bond, which can be con-
verted to the corresponding [2.2]MCP-1,2-dione.8
¤ Part 51: ref. 1.
DOI: 10.1039/b001145m
New J. Chem., 2000, 24, 221È228
221
This journal is ( The Royal Society of Chemistry and the Centre National de la Recherche ScientiÐque 2000

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protons at d 2.93. Thus, the methoxy protons should show an
upÐeld shift due to the ring current of the opposite aromatic
ring.19 These data strongly support the assignment of both
OH groups to endo-arrangement and therefore, anti-4a is
found to be a trans-diol.
The mass spectral data for dimer 5 (M` m/z \ 756) strongly
support a cyclic dimeric structure. In the 1H-NMR spectrum
of tetramethoxyMCP 5, protons of the tert-butyl and methoxy
groups, ArCH CH Ar methylene protons, and the
2
2
ArCH2CHAr oleÐnic protons each appear as a singlet at
27 ¡C. This behavior indicates that the rate of conformational
ring Ñipping of macrocycle 5 is faster than the NMR time
scale above this temperature. However, in dimer 5, even at
[60 ¡C in CDCl , the singlet signal of the ArCH CH Ar-
3
2
2
ethylene protons and the ArCH2CHAr oleÐnic protons
both remain unsplit. These observations indicate the Ñexible
structure of 5. In comparison with the corresponding
tetramethoxy[2.2.2.2]MCP 7,20 the ring size of 5 is smaller
and the methoxy group might come in close proximity to the
aromatic ring and thus the signal of the methoxy group might
shift to higher Ðeld. However, in fact the methoxy signal of
Scheme 1
formation of the unsaturated C2C linkage. Thus, during the
McMurry reaction the deoxygenation of the diol to form the
double bond might be quite difficult.
The structures of products anti-4a and 5 were determined
on the basis of their elemental analyses and spectral data.
Thus, we previously assigned18 the 1H-NMR signals of 1-exo-
5,13-trichloro-8,16-dimethyl[2.2]MCP. We have assigned the
1H-NMR signals of 4a in a similar fashion. For example, the
1H-NMR spectrum of 4a shows two internal methoxy reso-
nances as a singlet at d 2.93, a bridge methine signal as a
singlet at d 4.51, and two aromatic protons as a pair of doub-
lets at d 7.09 and 7.40 (J \ 2.5 Hz); the latter protons are in a
strongly deshielding region of the oxygen atom of endo-OH
on the ethylene bridge. The structure of the anti-conformer is
also readily assigned from the chemical shift of the methoxy
[2.2.2.2]diene
5 appears around d 3.51 and that of
[2.2.2.2]MCP 7 resonates at d 2.9. These Ðndings might indi-
cate that the conformation of 5 is quite di†erent from that of 7
due to the two additional double bonds of the ethylene bridge.
The X-ray crystallographic analysis of 5 clearly shows that
the four methoxy groups are located on the same side of the
ring and that the two double bond adopt cis-conÐgurations,
resulting in
a cone-conformation like tert-butylcalix[4]
arene.21 These results seem to indicate that the double bonds
in 5 play an important role in the Ðxation of the conformation
in the solid state (Fig. 1).
Similar McMurry cyclization of bis(formyl)diphenyl-
propane, 2b, carried out under the same reaction conditions
a†orded diol anti-4b in 29% yield, along with trace amounts
of syn-[2.3]MCP-1-ene, syn-3b, and 1,3-bis(5-tert-butyl-2-
methoxy-3-methylphenyl)propane, 6b. The same results were
obtained in the case of bis(formyl)diphenylbutane, 2c, except
that two types of [2.4]MCP-1-enes, anti- and syn-3c, were
formed. Interestingly, the increased and preferential formation
Scheme 2
Table
1 McMurry reaction of 1,n-bis(5-tert-butyl-3-formyl-2-
methoxyphenyl)alkanes, 2aÈ2d
Product yield/%a
Substrate
n
anti-3
syn-3
anti-4
6
2a
2ab
2b
2c
2c
2c
3
4
5
0
0
0
2.1
0
0
0
1.0
2.0
27.4
18.3
68.0
29.1
56.5
15.3
3.2
4.0
2.0
0
2d
0
Fig. 1 Ortep drawing of 5,13,21,29-tetra-tert-butyl-8,16,24,32-
tetramethoxy[2.2.2.2]MCP-1,18-diene, 5. Thermal ellipsoids are
drawn at the 50% probability level. Hydrogen atoms are omitted for
clarity.
a Isolated yields. b The reaction was carried out in the presence of
pyridine. c The dimer (Z,Z)-5 was obtained in 0.4 and 0.6% yields,
respectively.
222
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of syn-[2.5]MCP-1-ene, syn-3d, in 27% yield was observed in
the similar McMurry cyclization of bis(formyl)-
diphenylpentane, 2d. With increasing length of the methylene
bridge higher yields of [2.n]MCP-1-enes were obtained. This
Ðnding seems to support the notion that the strain of the
[2.2]MCP-1-ene compared to the higher [2.n]MCP-1-enes
decreases as the length of the methylene bridge increases.
The structures of products 3b and 3c were determined on
the basis of their elemental analyses and spectral data. For
example, the 1H-NMR spectrum of 3c shows two kinds of
methoxy protons, each as a singlet. By careful column chro-
matography (silica gel, Wako C-300), two conformers, anti-3c
and syn-3c, were separated. They are thermally stable and do
not interconvert at 180 ¡C in DMSO solution and at 400 ¡C in
the solid state. The 1H-NMR spectra of conformers anti-3c
and syn-3c respectively show the methoxy protons at d 3.26
and 3.70. The aromatic protons of conformer syn-3c are
observed at much higher Ðeld (d 6.46, 6.56) than those of con-
former anti-3c at d 6.80 and 6.95, due to the ring current e†ect
by the adjacent benzene ring,22 a common consequence of
face-to-face benzene rings. Also the tert-butyl protons of
syn-3c were observed at higher Ðeld, d 1.10, due to the strong
shielding e†ect of the benzene ring. The above data show that
the structure of anti-3c is the anti-conformer, whereas the
structure of syn-3c is the syn-conformer. Chemical shifts
similar to those of syn-3c were observed in syn-3b and syn-3d.
Although the parent [2.2]MCP was Ðrst reported as early
as 1899 by Pellegrin,23 the synthesis of syn-[2.2]MCP was
not realized until 85 years later. Mitchell et al.24 successfully
prepared syn-[2.2]MCP at low temperature by using
(arene)chromiumcarbonyl complexation to control the stereo-
chemistry. However, syn-[2.2]MCP isomerizes readily to the
anti-isomer above 0 ¡C. Finally, Ito et al.25 have isolated and
characterized syn-[2.2]MCP without complexation. However,
the preparation of internally substituted syn-[2.n]MCP-1-enes
having internal substituents has not been published so far. We
have thus accomplished for the Ðrst time the preparation of a
series of syn-[2.3]-, syn-[2.4]- and syn-[2.5]MCP-1-enes, syn-
3b–d. Also we have developed the convenient preparation of
[2.n]MCPs 4 having a 1,2-diol unit on the ethylene bridge.
The 1H-NMR spectrum of 4b shows two internal methoxy
protons as a singlet at d 3.07, a bridged methine proton as a
singlet at d 4.53, and two aromatic protons as a set of doub-
lets at d 7.03 and 7.43 (J \ 2.4 Hz). The higher Ðeld shift for
the methoxy protons strongly supports the structure of 4b as
Scheme 3
resulted only a mixture of anti-8a and anti-9a in almost the
same ratio. This Ðnding seems to support the strained nature
of the diketone 9a compared to the monoketone 8a, in spite of
these having the same ring size.
However, this diketone anti-9a was found to be quite labile
under treatment by silica gel column chromatography and on
reÑuxing in toluene to a†ord dicarboxylic acid 10 in quanti-
tative yield. Thus, a trapping reaction of anti-9a with o-
phenylenediamine was attempted, in which the crude diketone
anti-9a was treated with o-phenylenediamine in ethanol at
room temperature for 24 h to a†ord in almost quantitative
yield the desired [2.2]MCP anti-11 having a quinoxaline
skeleton (Scheme 4).
In contrast, in the case of [2.3]- and [2.4]MCPs, similar
Swern oxidation of the trans-diols anti-4b and anti-4c also
succeeded in a†ording the desired diketones anti-9b and
anti-9c in 92 and 100% yields, respectively, as stable yellow
prisms. This Ðnding seems to support the notion that the
strain of the [2.2]MCP diketone anti-9a compared to the
[2.3]- and [2.4]MCP diketones anti-9b and anti-9c increases
as the length of the methylene bridge decreases.
The structures of the diketones anti-9a–c were assigned on
the basis of elemental analyses and spectral data. The internal
methoxy protons and aromatic protons in the 1H-NMR spec-
trum and the carbonyl frequency in the IR spectrum are tabu-
lated in Table 3.
the anti-conformer.
A deshielded aromatic proton was
observed in the NMR spectrum of 4b at d 7.43, which is
almost the same as that for the endo-OH arrangement of 4a (d
7.40). Similar Ðndings were observed in the higher analogues
4c and 4d. On the basis of the spectral data, the two OH
groups of 4bÈd are both in endo-arrangement as in 4a and
therefore, all of the diols anti-4 are found to be trans-diol.
Although Mitchell and Weerawarna reported the Ðrst prep-
aration of [2.2]MCP-1,2-dione from oxidation of the corre-
sponding [2.2]MCP-1,2-diol,12 the physical and chemical
properties have not been established so far. Thus, there is sub-
stantial interest in the oxidation of [2.n]MCPs 4 having a 1,2-
diol to a†ord [2.n]MCP-1,2-diones.
An attempted oxidation of the trans-diol anti-4a to the 1,2-
dione anti-9a with pyridinium chlorochromate carried out in a
methylene dichloride solution under the same reaction condi-
tions as described above failed. Only the cleavage reaction
product, the dialdehyde 2a was obtained in 90% yield. This
Ðnding seems to support the strained nature of the diketone
anti-9a. Fortunately, Swern oxidation16 of anti-4a succeeded
in a†ording the desired [2.2]MCP diketone anti-9a in 12%
yield only, along with [2.2]MCP monoketone anti-8a and ring
cleavage reaction product 2a in 58 and 28% yields, respec-
tively (Scheme 3, Table 2). Prolonging the reaction time to
24 h at room temperature under the same reaction conditions
Table 2 Swern oxidation of [2.n]MCP-1,2-diols, anti-4aÈc
Product yield/%a,b
Substrate
n
anti-8
anti-9
2
4a
4bc
4c
2
3
4
58
0
0
12(8)
92(85)
100(95)
28
0
0
a Relative yields were determined by 1H-NMR spectroscopy.
b Isolated yields are shown in parentheses. c The starting compound
4b was recovered in 8% yield.
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223

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Scheme 4
The 1H-NMR spectrum of anti-8a shows internal methoxy
protons as singlets at d 2.93 and 3.04, a bridged methine
proton as a singlet at d 4.33, and two aromatic protons as two
sets of doublets at d 7.09, 7.34 and 7.28, 7.32 (J \ 2.4 Hz). We
observed one of the methoxy protons to be deshielded by the
carbonyl group on the ethylene bridge resulting in a downÐeld
shift (d 3.04 ppm). A deshielded aromatic proton was observed
at d 7.34 due to the endo-OH oxygen atom on the ethylene
bridge, which is almost the same as that for the endo-OH
arrangement of 4a (d 7.40).
Fig. 2 UV absorption spectra of [2.n]MCP ketones 9 and benzil, 12,
in cyclohexane.
The higher frequency of the C2O stretching vibration in the
IR spectrum for 9a (1678 cm~1) in comparison with that for
the reference compound benzil, 12 (1662 cm~1), presumably
reÑects the deviation of the carbonyl group from the plane of
the benzene ring rather than conjugation between the carbon-
yl group and the benzene ring. This Ðnding is similar to those
for the strained [2.2]paracyclophan-1-ones,6,26 and
[2.2]metacyclophan-1-ones,27 for which absorptions are
toward wavelengths characteristic of unconjugated ketones
due to the expanded OÈCÈC bond angles. A similar high fre-
quency was observed in the next member of the series,
[2.3]MCP-1,2-dione 9b (1675 cm~1), but increasing by one
the methylene bridge, the C2O stretching vibration appears at
the normal position in [2.4]MCP-1,2-dione, 9c (1667 cm~1).
The UV spectra of the diketones 9a–c along with that of the
reference compound benzil, 12, in cyclohexane are shown in
Fig. 2. The UV spectra of the diketones 9 show di†erent
absorption curves than that of the model acyclic compound.
The lack of a benzil-type chromophore in the UV spectra of
the MCP ketones conÐrms the non-planarity of the aromatic
ring and carbonyl group.
hydrogen atoms are not shown. The structures were solved by
direct methods and reÐned using standard least-squares and
Fourier techniques.
Compound anti-9a crystallized in the centrosymmetric
space group P2 /a. In contrast, compound anti-9b crystallized
1
in the centroasymmetric space group Pa and there are two
independent molecules (Z \ 4) at general positions in the
asymmetric unit of the crystal structure. Thus, one molecule is
selected and depicted in Fig. 4. It is clear that both anti-9a and
anti-9b adopt the anti conformation in which two benzene
rings are in a non-planar chain form. In anti-9a the benzene
Bathochromic shifts were observed for the cyclophane dike-
tones 9a–c, which are ascribed to a transannular interaction
between the two benzene rings and an increase in the strain of
these systems.28 With decreasing length of the methylene
bridge red shifts of the absorption derived from nÈp* tran-
sition were obtained. This supports the notion that the strain
in the MCP-1,2-diones decreases as the length of the methy-
lene bridge increases.
Single-crystal X-ray di†raction structures of the diketones
anti-9a and anti-9b are shown in Fig. 3 and 4. For clarity all
Table 3 Spectral data of [2.n]MCP-1,2-diones (anti-9aÈc)
NMR/da
Methoxy Aromatic Protons
Compound
n
protons
Ha
Hb
IR t
/cm~1
C/O
anti-9a
anti-9b
anti-9c
2
3
4
3.11
3.19
3.28
7.32
7.33
7.16
7.34
7.49
7.83
1678
1675
1667
Fig. 3 Ortep drawing of anti-5,13-di-tert-butyl-8,16-dimethoxy[2.2]
MCP-1,2-dione, anti-9a. Thermal ellipsoids are drawn at the 50%
probability level. Hydrogen atoms are omitted for clarity.
a Determined in CDCl using SiMe as a reference.
3
4
224
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are 120.9¡ and 121.0¡, respectively. Two methyl groups in
internal and methoxy groups of anti-9b are located under-
neath and over two methyl ring planes. It is quite interesting
that two internal methoxy groups of anti-9a point towards the
carbonyl groups of the bridge chains. This might contribute to
avoiding steric crowding among the oxygen and hydrogen
atoms of the bridge chains.
In conclusion, we have developed the convenient prep-
aration of a series of syn- and anti-[2.n]MCP-1-enes 3
and [2.n]MCP-1,2-diols 4 by a McMurry cyclization of
1,n-bis(5-tert-butyl-3-formyl-2-methoxyphenyl)alkanes 2. Also,
[2.n]MCP-1,2-diols 4 were converted to the 1,2-diones 9 by
Swern oxidation. Further studies on the chemical properties
of the diketones 9 are now in progress.
Experimental
All melting points (Yanagimoto MP-S1) are uncorrected.
NMR spectra were determined at 270 M Hz with a Nippon
Denshi JEOL FT-270 NMR spectrometer with SiMe as an
4
internal reference: J values are given in Hz. IR spectra were
measured for samples as KBr pellets or as liquid Ðlms on
NaCl plates in a Nippon Denshi JIR-AQ2OM spectropho-
tometer. UV spectra were measured by a Shimadzu 240 spec-
trophotometer. Mass spectra were obtained on a Nippon
Denshi JMS-01SA-2 spectrometer at an ionization energy of
70 eV using a direct inlet system through GLC. Elemental
analyses were performed by Yanaco MT-5. GLC analyses
were performed with
a Shimadzu gas chromatograph,
GC-14A; silicone OV-1, 2m; programmed temperature rise,
12 ¡C min~1, carrier gas nitrogen, 25 mL min~1.
Synthesis of 1,n-bis(5-tert-butyl-2-methoxyphenyl)alkanes, 1,
was previously described.17,29
Fig. 4 Ortep drawing of anti-5,14-di-tert-butyl-8,17-dimethoxy[2.3]
MCP-1,2-dione, anti-9b. Thermal ellipsoids are drawn at the 50%
probability level. Hydrogen atoms are omitted for clarity.
General procedure for the synthesis of
rings deviate from planarity to some extent and the C5, C8,
C13 and C16 carbons are out of the C3ÈC4ÈC6ÈC7 and C11È
C12ÈC14ÈC15 planes. The dihedral angles of the C3ÈC4ÈC6È
C7 plane between the C4ÈC5ÈC6 and C8ÈC3ÈC7 planes, and
those of the C11ÈC12ÈC14ÈC15 plane between the C12ÈC13È
C14 and C16ÈC11ÈC15 planes are 6.1¡, 12.0¡, 6.7¡ and 15.7¡,
respectively, showing that this molecule has an asymmetrical
strain between the above and below rings, and that the
amount of strain is much greater at the internal carbons, C8
and C16, than at the external carbons, C5 and C13. The C1È
C2ÈC3ÈO2 and C15ÈC1ÈC2ÈO1 planes are twisted out of
coplanarity and have a dihedral angle of 5.2¡, and thus the
two carbonyl groups, C1ÈO1 and C2ÈO2 do not lie in the
same plane where the adjacent two carbon atoms are
included. The angles of C1ÈC2ÈC3 and C15ÈC1ÈC2 are 119.8¡
and 122.4¡, respectively, which are not so di†erent from the
values in the acyclic diaryl ketones in spite of the di†erence of
2.6¡.
The two benzene ring framework in anti-9b also features a
slight twisting of the dihedral angles from planarity and the
C6, C9, C14 and C17 carbons are out of the C5ÈC7ÈC8ÈC4
and C12ÈC13ÈC15ÈC16 planes. The dihedral angles of the
C5ÈC7ÈC8ÈC4 plane between the C4ÈC8ÈC9 and C5ÈC6ÈC7
planes, and those of the C12ÈC13ÈC15ÈC16 plane between
the C16ÈC12ÈC17 and C13ÈC14ÈC15 planes are 11.4¡, 5.3¡,
9.6¡ and 6.3¡, respectively. In the other independent molecule,
the corresponding values for the dihedral angles are 11.0¡,
5.6¡, 9.5¡ and 6.6¡. These imply that this molecule has less
strain than anti-9a. However, it is noted that the C8ÈC10È
C11ÈO2 and C10ÈC11ÈC12ÈO3 planes have a dihedral angle
of 20.0¡, which is signiÐcantly much larger than that in anti-
9a. Similarly, in the other independent molecule, the corre-
sponding values for the dihedral angles are 20.4¡. The angles
between C8ÈC10ÈC11 and C10ÈC11ÈC12 are almost the
same, 121.3¡ and 120.5¡, respectively. In the case of the other
independent molecule, the corresponding values for the angles
1,n-bis(5-tert-butyl-3-formyl-2-methoxyphenyl)alkanes, 2
To a solution of 1,2-bis(5-tert-butyl-2-methoxyphenyl)ethane,
1a,29 (3.19 g, 9 mmol) and Cl CHOMe (2.28 mL, 25.2 mmol)
2
in CH Cl (20 mL) was added a solution of TiCl (6.0 mL,
2
2
4
54.5 mmol) in CH Cl (20 mL) at 0 ¡C. After the reaction
2
2
mixture was stirred at room temperature for 2 h, it was
poured into a large amount of iceÈwater (200 mL) and
extracted with CH Cl (100 mL ] 3). The combined extracts
2
2
were washed with water, dried with Na SO and concen-
2
4
trated. The residue was chromatographed over silica gel
(Wako C-300, 200 g) with CHCl as eluent to give crude 2a
3
(3.0 g, 81%). Recrystallization from hexane gave 1.44 g (39%)
of 1,2-bis(5-tert-butyl-3-formyl-2-methoxyphenyl)ethane, 2a, as
colourless prisms, mp 119È120 ¡C; t
(KBr)/cm~1: 1683
max
(C2O); d (CDCl ): 1.26 (18H, s), 3.00 (4H, s), 3.87 (6H, s), 7.36
H
3
(2H, d, J 2.5), 7.70 (2H, d, J 2.5), 10.35 (2H, s); m/z: 410 (M`).
Anal. calcd. for C
C, 76.27; H, 8.49.
H
O (410.56): C, 76.06; H, 8.35. Found:
26 34
4
1,3-Bis(5-tert-butyl-3-formyl-2-methoxyphenyl)propane, 2b.
2b was prepared as described above, yield 67%; yellow
viscous oil; t
(NaCl)/cm~1: 1688 (C2O); d (CDCl ): 1.32
max
H
3
(18H, s), 1.92È2.05 (2H, m), 2.76 (4H, t, J 7.6), 3.84 (6H, s), 7.50
(2H, d, J 2.4), 7.73 (2H, d, J 2.4), 10.36 (2H, s); m/z: 424 (M`).
Anal. calcd. for C
C, 75.64; H, 8.63.
H
O (424.59): C, 75.38; H, 8.55. Found:
27 36
4
1,4-Bis(5-tert-butyl-3-formyl-2-methoxyphenyl)butane, 2c. 2c
was prepared as described above, yield 60%; colourless prisms
(hexaneÈbenzene, 5 : 1), mp 123È125 ¡C; t
(KBr)/cm~1:
max
1688 (C2O); d (CDCl ): 1.31 (18H, s), 1.70È1.80 (4H, m),
H
3
2.70È2.80 (4H, m), 3.87 (6H, s), 7.48 (2H, d, J 2.4), 7.77 (2H, d,
J 2.4), 10.36 (2H, s); m/z: 438 (M`). Anal. calcd. for C
(438.61): C, 76.68; H, 8.73. Found: C, 77.00; H, 8.86.
H
O
28 38
4
New J. Chem., 2000, 24, 221È228
225

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1,5-Bis(5-tert-butyl-3-formyl-2-methoxyphenyl)pentane, 2d.
2d was prepared as described above, yield 42%; colourless
anti-5,15-Di-tert-butyl-8,18-dimethoxy[2.4]metacyclophan-
1-ene, anti-3c. anti-3c was obtained as colourless prisms
(MeOH), mp 168È169 ¡C; d (CDCl ): 1.20È1.40 (4H, m), 1.31
prisms (hexane), mp 89È90 ¡C; t
(KBr)/cm~1: 1692 (C2O);
max
H
3
d
(CDCl ): 1.31 (18H, s), 1.48È1.53 (2H, m), 1.64È1.70 (4H,
(18H, s), 1.96È2.08 (2H, m), 2.78È2.85 (2H, m), 3.26 (6H, s), 6.61
(2H, s), 6.80 (2H, d, J 2.8), 6.95 (2H, d, J 2.8); m/z: 406 (M`).
H
3
m), 2.65È2.71 (4H, m), 3.87 (6H, s), 7.47 (2H, d, J 2.4), 7.71 (2H,
d, J 2.4), 10.36 (2H, s); m/z: 452 (M`). Anal. calcd. for
Anal. calcd. for C
C, 82.50; H, 9.60.
H
O (406.61): C, 82.71; H, 9.42. Found:
28 38
2
C
8.74.
H
O (452.64): C, 76.95; H, 8.91. Found: C, 77.01; H,
29 40
4
syn-5,15-Di-tert-butyl-8,18-dimethoxy[2.4]metacyclophan-
1-ene, syn-3c. syn-3c was obtained as colourless prisms
(MeOH), mp 126È129 ¡C; d (CDCl ): 1.10 (18H, s), 1.30È1.42
General procedure for the McMurry coupling reaction of 2
H
3
(2H, m), 1.92È2.15 (4H, m), 2.72È2.82 (2H, m), 3.70 (6H, s), 6.46
(2H, d, J 2.4), 6.56 (2H, d, J 2.4), 6.97 (2H, s); m/z: 406 (M`).
The McMurry reagent was prepared from TiCl (13.75 mL,
4
125 mmol) and Zn powder (18 g, 275 mmol) in 500 mL of dry
Anal. calcd. for C
C, 82.41; H, 9.44
H
O (406.61): C, 82.71; H, 9.42. Found:
THF, under nitrogen. A solution of 1,2-bis(5-tert-butyl-3-
formyl-2-methoxyphenyl)ethane, 2a, (1.23 g, 3 mmol) in dry
THF (100 mL) was added within 60 h to the black mixture of
the McMurry reagent by using a high-dilution technique with
continuous reÑuxing and stirring. The reaction mixture was
reÑuxed for an additional 8 h, cooled to room temperature
and hydrolized with aqueous 10% K CO (200 mL) at 0 ¡C.
28 38
2
anti-1,2-endo-Dihydroxy-5,15-di-tert-butyl-8,18-dimethoxy-
[2.4]metacyclophane, anti-4c. anti-4c was obtained as colour-
less prisms (hexaneÈbenzene, 10 : 1), mp 191È194 ¡C; t
max
(KBr)/cm~1: 3521, 3378 (OH); d (CDCl ): 1.37 (18H, s),
H
3
2
3
1.22È1.38 (4H, m), 1.95È2.02 (2H, m), 2.71È2.82 (2H, m), 2.85
The reaction mixture was extracted with CH Cl (200
2
2
(2H, s, replaced by D O), 3.23 (6H, s), 4.70 (2H, s), 6.86 (2H, d,
mL ] 3). The combined extracts were washed with water,
2
J 2.4), 7.49 (2H, d, J 2.4): m/z: 440 (M`). Anal. calcd. for
dried with Na SO and concentrated.
2
4
C
8.84.
H
O (440.63): C, 76.33; H, 9.15. Found: C, 76.17; H,
For 2a the residue was chromatographed over silica gel
(Wako C-300, 100 g) with hexane, benzene and CHCl as
28 40
4
3
eluents to give 6a, (Z,Z)-5 and anti-4a, respectively. The
syn-5,14-Di-tert-butyl-8,17-dimethoxy[2.3]metacyclophan-
1-ene, syn-3b. syn-3b was obtained as a colourless oil; d
eluents were recrystallized from hexane, methanol and
hexaneÈbenzene (1 : 1) to a†ord 6a (37 mg, 3.2%), (Z,Z)-5 (4.3
mg, 0.38%) and anti-4a (230 mg, 18.3%), respectively.
The McMurry coupling reaction of 2a was also carried out
in the presence of pyridine (22.5 mL, 200 mmol added to the
2a-THF solution) to a†ord 6a (46 mg, 4.0%), (Z,Z)-5 (6.8 mg,
0.6%) and anti-4a (855 mg, 68%).
H
(CDCl ): 1.09 (18H, s), 1.82È2.60 (4H, m), 3.02È3.15 (2H, m),
3
3.71 (6H, s), 6.24 (2H, d, J 2.4), 6.58 (2H, d, J 2.4), 6.98 (2H, s);
m/z: 392 (M`). Anal. calcd. for C
H, 9.24. Found: C, 82.38; H, 9.07.
H
O (392.59): C, 82.61;
27 36
2
1,3-Bis(5-tert-butyl-2-methoxy-3-methylphenyl)propane, 6b.
6b was obtained as a colourless oil; d (CDCl ): 1.28 (18H, s),
For 2bÈ2d, after concentration of the combined extracts, the
residue was treated with hexane (10 mL) to give a precipitate.
The precipitate was Ðltered and washed with hexane (5 mL) to
give a colourless solid, which was recrystallized from hexaneÈ
benzene, 10 : 1, to a†ord anti-4c (746 mg, 56.5%) from 2c. The
Ðltrate was concentrated and the residue was chromato-
graphed over silica gel (Wako C-300, 100 g) with hexaneÈ
benzene (1 : 1) and benzene as eluents to give anti-3c (26 mg,
2%) and syn-3c (25 mg, 2%), respectively.
H
3
1.65È1.77 (2H, m), 2.28 (6H, s), 2.71 (4H, t, J 8.1), 3.69 (6H, s),
7.01 (2H, d, J 2.4), 7.05 (2H, d, J 2.4); m/z: 396 (M`). Anal.
calcd. for C
81.51; H, 10.05.
H
O (396.62): C, 81.77; H, 10.17. Found: C,
27 40
2
anti-1,2-endo-Dihydroxy-5,14-di-tert-butyl-8,17-dimethoxy-
[2.3]metacyclophane, anti-4b. anti-4b was obtained as colour-
less prisms (hexaneÈbenzene, 5 : 1), mp 235È237 ¡C; t
Compounds syn-3b, syn-3d, anti-4b, anti-4d and 6b were
similarly prepared. The yields are listed in Table 1.
max
(KBr)/cm~1: 3553, 3423 (OH): d (CDCl ): 1.33 (18H, s),
H
3
1.94È2.04 (2H, m), 2.37È2.49 (2H, m), 2.57È2.68 (2H, m), 2.76
(2H, s, replaced by D O), 3.07 (6H, s), 4.53 (2H, s), 7.03 (2H, d,
2
J 2.4), 7.43 (2H, d, J 2.4); m/z: 426 (M`). Anal. calcd. for
C
8.84.
H
O (426.6): C, 76.02; H, 8.98. Found: C, 76.17; H,
1,2-Bis(5-tert-butyl-2-methoxy-3-methylphenyl)ethane, 6a. 6a
27 38
4
was obtained as colourless prisms (hexane), mp 100 ¡C; d
H
(CDCl ): 1.28 (18H, s), 2.30 (6H, s), 2.91 (4H, s), 3.72 (6H, s),
3
syn-5,16-Di-tert-butyl-8,19-dimethoxy[2.5]metacyclophan-
1-ene, syn-3d. syn-3d was obtained as colourless prisms
(methanol), mp 125È127 ¡C; d (CDCl ): 1.12 (18H, s), 1.10È
1.22 (4H, m), 1.53È1.69 (2H, m), 2.07È2.18 (2H, m), 2.91È3.02
(2H, m), 3.70 (6H, s), 6.58 (2H, d, J 2.7), 6.68 (2H, d, J 2.7), 6.96
7.02 (2H, d, J 2.4), 7.05 (2H, d, J 2.4); m/z: 382 (M`). Anal.
calcd. for C
81.41; H, 10.05
H
O (382.59): C, 81.62; H, 10.01. Found: C,
26 38
2
H
3
(Z,Z)-5,13,21,29-Tetra-tert-butyl-8,16,24,32-tetramethoxy-
[2.2.2.2]metacyclophane-1,18-diene, (Z,Z)-5. 5 was obtained
as colourless prisms (MeOH), mp 227È228 ¡C; d (CDCl ):
(2H, s); m/z: 420 (M`). Anal. calcd. for C
82.81; H, 9.58. Found: C, 82.55; H, 9.61.
H
O (420.64): C,
29 40
2
H
3
1.11 (36H, s), 2.75 (8H, s), 3.51 (12H, s), 6.73 (4H, s), 6.79 (4H,
anti-1,2-endo-Dihydroxy-5,16-di-tert-butyl-8,19-dimethoxy-
[2.5]metacyclophane, anti-4d. anti-4d was obtained as colour-
less prisms (hexaneÈbenzene, 5 : 1), mp 224È226 ¡C; t
(KBr)/cm~1: 3386 (OH); d (CDCl ): 1.32 (18H, s), 1.15È1.35
(6H, m), 1.98È2.11 (2H, m), 2.48È2.59 (2H, m), 2.81 (2H, s,
replaced by D O), 3.32 (6H, s), 4.85 (2H, s), 6.93 (2H, d, J 2.4),
7.47 (2H, d, J 2.4); m/z: 454 (M`). Anal. calcd. for C
(454.66): C, 76.61; H, 9.31. Found: C, 76.44; H, 9.33.
d, J 2.5), 7.00 (4H, d, J 2.5); m/z: 756 (M`). Anal. calcd. for
C
H
8.98.
O (757.12): C, 82.49; H, 9.05. Found: C, 82.78; H,
52 68
4
max
H
3
anti-1,2-endo-Dihydroxy-5,13-di-tert-butyl-8,16-dimethoxy-
[2.2]metacyclophane, anti-4a. anti-4a was obtained as colour-
2
H
O
less prisms (hexaneÈbenzene, 1 : 1) mp 252 ¡C; t
(KBr)/
29 42
4
max
cm~1: 3426 (OH); d (CDCl ): 1.32 (18H, s), 2.52È2.71 (4H,
H
3
m), 2.81 (2H, s, OH, H/D exchange with D O), 2.93 (6H, s),
Oxidation of anti-4a with C H NH‘CrO Cl—
2
5
5
3
4.51 (2H, s), 7.09 (2H, d, J 2.5 Hz), 7.40 (2H, d, J 2.5); m/z: 412
(M`). Anal. calcd. for C
Found: C, 75.69; H, 8.69.
H
O
(412.57): C, 75.69; H, 8.8.
To a solution of anti-4a (86.3 mg, 0.219 mmol) and CH Cl
26 36
4
2
2
(7.5 mL) was added C H NH`CrO Cl~ (480 mg, 1.86 mmol)
5
5
3
226
New J. Chem., 2000, 24, 221È228

View Article Online
at 0 ¡C. The reaction mixture was stirred at room temperature
for 12 h. The reaction mixture was Ðltered and the Ðltrate was
extracted with CH Cl (10 mL ] 3). The extract was dried
over anhydrous sodium sulfate and concentrated. The residue
was subjected to silica gel (Wako, C-300; 100 g) column chro-
matography using benzene as eluent to give 1,2-bis(5-tert-
butyl-3-formyl-2-methoxyphenyl)ethane, 2a (61 mg, 90%) as
colourless prisms.
(1H, s), 5.26 (1H, s, OH, H/D exchange with D O), 7.09 (1H, d,
J 2.4), 7.28 (1H, d, J 2.4), 7.32 (1H, d, J 2.4), 7.34 (1H, d, J 2.4).
2
2
2
anti-5,14-Di-tert-butyl-8,17-dimethoxy[2.3]metacyclophane-
1,2-dione, anti-9b. anti-9b was obtained as yellow prisms
(hexaneÈbenzene, 5 : 1), mp 274È276 ¡C; t
(KBr)/cm~1:
max
1675 (C2O); d (CDCl ): 1.34 (18H, s), 1.90È2.05 (2H, m),
H
3
2.36È2.44 (4H, m), 3.19 (6H, s), 7.33 (2H, d, J 2.4 Hz), 7.49 (2H,
d, J 2.4); m/z: 422 (M`). Anal. calcd. for C
C, 76.74; H, 8.11. Found: C, 76.93; H, 7.98.
H
O (422.57):
Swern oxidation of anti-4a
27 34
4
To a solution of oxalyl chloride (0.25 mL, 2.75 mmol) in
CH Cl (25.0 mL) was added DMSO (0.126 mL, 1.65 mmol)
anti-5,15-Di-tert-butyl-8,18-dimethoxy[2.4]metacyclophane-
1,2-dione, anti-9c. anti-9c was obtained as yellow prisms
2
2
and then anti-4a (110 mg, 0.331 mmol) in CH Cl (1.0 mL) at
2
2
[30 ¡C under nitrogen. After the reaction mixture had been
stirred at [30 ¡C for 1 h, triethylamine (380 mg, 3.75 mmol)
was added. The temperature of the reaction mixture was
maintained at [30 ¡C for 30 min under nitrogen, then
allowed to warm up to room temperature and stirred for an
additional 1 h. Then, water (10 mL) was added and the reac-
tion mixture was extracted with CH Cl (10 mL ] 3). The
(hexaneÈbenzene, 5 : 1), mp 245È246 ¡C; t
(KBr)/cm~1:
max
1667 (C2O); d (CDCl ): 1.17È1.39 (4H, m), 1.34 (18H, s),
H
3
2.07È2.24 (2H, m), 2.78È2.91 (2H, m), 3.28 (6H, s), 7.16 (2H, d,
J 2.4), 7.83 (2H, d, J 2.4); m/z: 436 (M`). Anal. calcd. for
C
8.41.
H
O (436.6): C, 77.03; H, 8.31. Found: C, 77.00; H,
28 36
4
2
2
dichloromethane solution was washed with water, dried over
Trapping reaction of anti-9a with o-phenylenediamine
Na SO and evaporated in vacuo to a residue. The 1H-NMR
2
4
To a solution of crude anti-9a (10.6 mg, 0.026 mmol) in
ethanol (10 mL) was added o-phenylenediamine (28.3 mg,
0.262 mmol) at room temperature. After the reaction mixture
had been stirred at room temperature for 24 h, the solvent was
evaporated in vacuo to leave a residue. The residue was
washed successively with 10% aqueous hydrochloric acid,
water, and ethanol to a†ord anti-11 (12.5 mg, 100%) as a
brown solid, mp [300 ¡C; d (CDCl ): 1.34 (18H, s), 2.55È
spectrum of this oil was in accord with its being a mixture of
three components, anti-8a, anti-9a and 2a in the ratio of
58 : 12 : 28, which was crystallized by adding a small amount
of hexane to give a colourless solid. While attempts to isolate
pure anti-8a failed, recrystallization from hexaneÈCH Cl ,
2
2
10 : 1, a†orded anti-5,13-di-tert-butyl-8,16-dimethoxy[2.2]
metacyclophane-1,2-dione, anti-9a (10 mg, 8%) as orange
prisms, mp 193 ¡C;
t
(KBr)/cm~1: 1678 (C2O); d
H
3
max
H
2.80 (4H, m), 2.98 (6H, s), 7.19 (2H, d, J 2.4), 7.32 (2H, d, J 2.4),
7.78 (2H, dd, J 3.7, 6.3), 8.23 (2H, dd, J 3.7, 6.3); m/z: 480
(CDCl ): 1.33 (18H, s), 2.56 (2H, d, J 7.9), 2.86 (2H, d, J 7.9),
3
3.11 (6H, s), 7.32 (2H, d, J 2.4), 7.34 (2H, d, J 2.4); m/z: 408
(M`). Anal. calcd. for C
7.55; N, 5.83. Found: C, 79.69; H, 7.76; N, 5.62.
H
N O (480.66): C, 79.97; H,
(M`). Anal. calcd. for C
Found: C, 75.29; H, 8.09.
H
O (408.54): C, 75.44; H, 7.9.
32 36
2 2
26 32
4
Compounds anti-9b,c were similarly prepared. The yields
are listed in Table 2.
Crystal data for 5, anti-9a and anti-9b
Diketone anti-9a was found to be quite labile to treatment
by silica gel column chromatography and on reÑuxing in
toluene, a†ording dicarboxylic acid 10 in quantitative yield as
Crystallographic data for 5, anti-9a and anti-9b are given in
Table 4.
As a typical procedure, the unit cell constants for 5 were
derived from least-squares analysis of the settings of a CAD4
FR 586 di†ractometer for 25 reÑections, in the range of
24.0 \ h \ 27.4¡. The intensities of all independent reÑections
with 6.16¡ \ 2h \ 129.90¡ were measured with u scan width
colourless prisms (benzene), mp 213È215 ¡C; t
(KBr)/cm~1:
max
3410È2965, 1696 (C2O), 1603, 1479, 1274, 1238, 891; d
H
(CDCl ): 1.28 (18H, s), 3.02 (4H, s), 3.92 (6H, s), 7.33 (2H, d, J
2.4), 7.98 (2H, d, J 2.4), 11.15 (2H, s, OH); m/z: 442 (M`).
3
Anal. calcd. for C
C, 70.39; H, 7.89.
H
O (442.56): C, 70.56; H, 7.74. Found:
(0.8 ] 0.140 tan h); Ni-Ðltered Cu K radiation (j \ 1.581 84
26 34
6
a
A) was used. The X-ray analysis was performed with MolEN
program package30 and the structure was solved uneventfully
by direct methods (SIR88).31 The reÐnement was used by full-
matrix least squares.
anti-5,13-Di-tert-butyl-2-endo-hydroxy-8,16-dimethoxy-
[2.2]metacyclophan-1-one, anti-8a. d (CDCl ): 1.30 (9H, s),
H
3
1.32 (9H, s), 2.93 (3H, s), 3.04 (3H, s), 2.56È2.86 (4H, m), 4.33
CCDC reference number 440/167.
Table 4 Crystallographic data and data collection details for 5,13,21,29-tetra-tert-butyl-8,16,24,32-tetramethoxy[2.2.2.2]MCP-1,18-diene (5),
anti-5,13-di-tert-butyl-8,16-dimethoxy[2.2]MCP-1,2-dione (anti-9a) and anti-5,14-di-tert-butyl-8,17-dimethoxy[2.3]MCP-1,2-dione (anti-9b)
5
anti-9a
anti-9b
Formula
FW
C
757.1
H
O
C
408.54
H
O
C
422.57
H
O
52 68
4
26 32
4
27 34
4
Crystal system
Space group
Monoclinic
Monoclinic
Monoclinic
Pa (No.7)
12.834(1)
19.5775(16)
10.3418(5)
111.643(5)
2415.3(3)
4
298
5.74
0.076
0.108
P2 /n (No. 14)
P2 /a (No.14)
1
1
a/A
b/A
c/A
b/¡
17.1301(1)
23.052(2)
26.617(3)
10.267(1)
95.978(8)
4656.0(8)
4
295
4.80
0.085
0.114
8587
7423
9.7452(1)
10.1413(8)
93.239(6)
2274.5(3)
4
297
5.95
0.095
0.155
6260
4685
U/A
Ž
3
Z
T /K
k/cm~1
Ra
R
a
w
No. of reÑections
Unique reÑections
5128
4707
a w \ 4(F )2/[(rI )2 ] 0.0016(F )4].
o
o
o
New J. Chem., 2000, 24, 221È228
227

View Article Online
M. Tashiro, J. Chem. Soc., Perkin T rans. 1, 1992, 2675; (c) T.
Yamato, A. Miyazawa and M. Tashiro, J. Chem. Soc., Perkin
T rans. 1, 1993, 3127; (d) T. Yamato, Y. Saruwatari, L. K. Doa-
mekpor, K. Hasegawa and M. Koike, Chem. Ber., 1993, 126,
2501.
References
1
T. Yamato, H. Kamimura and H. Tsuzuki, Can. J. Chem., 2000,
78, 238.
2
3
4
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