Medium-sized cyclophanes. Part 55. Synthesis and conformational studies of [2.1.1] orthocyclophanes

Article abstract of DOI:10.1039/b008258i

[2.1.1]Orthocyclophanes 2 are prepared by pyrolysis of the corresponding 2-thia[3.1.1]orthocyclophane 2,2-dioxides 9, which are prepared by the reaction of 1,2-bis(2-bromomethylbenzyl)benzenes 7 with Na₂S in ethanol under high dilution conditions, followed by oxidation with m-chloroperbenzoic acid. The conformational studies on [2.1.1]orthocyclophanes 2, which adopt flexible saddle and crown structures in comparison with the corresponding 10,15-dihydro-5H-tribenzo[a,d,g]cyclononene ([1.1.1]orthocyclophane) 1, are discussed.

Full text of DOI:10.1039/b008258i

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Medium-sized cyclophanes. Part 55.¤ Synthesis and conformational
studies of [2.1.1]orthocyclophanes
Takehiko Yamato,*a Naozumi Sakaue,a Kan Tanakab and Hirohisa Tsuzukic
a Department of Applied Chemistry, Faculty of Science and Engineering, Saga University,
Honjo-machi 1, Saga-shi, Saga 840-8502, Japan. E-mail: yamatot=cc.saga-u.ac.jp;
Fax: ]81 0952 28 8591
b Department of Industrial Chemistry, Faculty of Science and Engineering, T ohwa University,
1-1-1 Chikushigaoka, Minami-ku, Fukuoka-shi, Fukuoka 815-8510, Japan
c 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) 9th October 2000, Accepted 4th December 2000
First published as an Advance Article on the web 22nd February 2001
[2.1.1]Orthocyclophanes 2 are prepared by pyrolysis of the corresponding 2-thia[3.1.1]orthocyclophane 2,2-
dioxides 9, which are prepared by the reaction of 1,2-bis(2-bromomethylbenzyl)benzenes 7 with Na S in ethanol
2
under high dilution conditions, followed by oxidation with m-chloroperbenzoic acid. The conformational studies on
[2.1.1]orthocyclophanes 2, which adopt Ñexible saddle and crown structures in comparison with the corresponding
10,15-dihydro-5H-tribenzo[a,d,g]cyclononene ([1.1.1]orthocyclophane) 1, are discussed.
One of the most interesting properties of [1.1.1]ortho-
cyclophane 1 (10,15-dihydro-5H-tribenzo[a,d,g]cyclononene)
and its congeners is their stable crown conformation, evi-
denced, in 1H-NMR spectra, by the characteristic AX quartet
of the methylene bridges.2 Thus, the pseudo-axial protons
[2.1.1]orthocyclophane 2 (Fig. 2). Thus, in contrast to
[1.1.1]orthocyclophanes,2 the conformational isomerism in
the present system is slightly more complicated. Furthermore,
the conformations of 2 are undetermined so far. Thus, there is
substantial interest in investigating the e†ects of the ethylene
bridge on their conformations. We report here the preparation
of [2.1.1]orthocyclophanes 2 using the sulfur method and
studies on their conformations in solution and the solid state.
(H ) resonate 1.2 ppm downÐeld with respect to their pseudo-
ax
equatorial counterparts (H ), a consequence of the steric com-
eq
pression. From the X-ray crystallographic studies of
cyclotriveratrylenes, that is 10,15-dihydro-2,3,7,8,12,13-hexa-
Results and discussion
methoxy-5H-tribenzo[a,d,g]cyclononenes,3
the
aromatic
hydrogen atoms of two adjacent rings [e.g. H(1) and H(14)]
are almost within contact distance (2.5 ^ 0.1 A between their
centers) and thus there is not much room in these positions for
a substituent, unless it is small. The activation barrier for the
crown-to-crown interconversion in cyclotriveratrylenes has
been found to be 26.5 kcal mol~1.4 Destabilization of the
crown may arise from steric hindrance created either by
geminal substitution of one methylene group5 or by the pres-
ence of bulky substituents6 such as a bromine atom or an allyl
group in the aromatic positions ortho to the 9-membered ring,
an exception being the methoxy group.7
Synthesis of [2.1.1]orthocyclophanes
The chemistry of medium- and large-sized bridged aromatics
with one or two aromatic rings has been extensively studied.8
Recently, many examples of compounds containing three or
more aromatic rings have been reported9,10 and these are
Although there are two possible conformational isomers for
1: crown and saddle conformation (Fig. 1), three di†erent
conformational isomers: crown, anti-saddle and syn-saddle
conformers are possible for 2, with the syn-saddle conformer
now being included, due to the ethylene bridge in
Fig. 1 Two possible conformations of [1.1.1]orthocyclophanes 1.
¤ For Part 54, see: ref. 1.
Fig. 2 Conformations of [2.1.1]orthocyclophanes 2.
434
New J. Chem., 2001, 25, 434È439
DOI: 10.1039/b008258i
This journal is ( The Royal Society of Chemistry and the Centre National de la Recherche ScientiÐque 2001

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mostly oligomers formed as by-products during the synthesis
of smaller members.11 We have previously described12 the
convenient and efficient method of Lewis acid or NaÐon-H (a
solid perÑuorinated resin sulfonic acid) catalyzed FriedelÈ
Crafts cyclibenzylation of 2,2@-bis(hydroxymethyl)diphenyl-
methanes with arenes to a†ord 10,15-dihydro-5H-tribenzo[a,
d,g]cyclononenes 1 under relatively mild reaction conditions,
in which an arene molecule is directly incorporated into the
cyclic system as a phenylene unit.
45% yield, respectively (Scheme 2). Oxidation of 8a,b with m-
chloroperbenzoic acid (m-CPBA) furnished the corresponding
sulfones 9a,b in almost quantitative yields. Pyrolysis of 9a,b
under reduced pressure (1 mmHg) was carried out according
to the reported method16 to a†ord 2a,b in 97 and 91% yields,
respectively. T rans-tert-butylation of 2b using AlCl È
3
MeNO 17 as catalyst in benzene succeeded in providing de-
2
tert-butylated product 2a in 70% yield along with tert-
butylbenzene. No concomitant ring cleavage such as
transbenzylation was observed under the reaction conditions.
The structures of 2a and 2b were elucidated based on their
elemental analyses and spectral data. In particular, the mass
spectral data for 2a and 2b (M` \ 284 and 396) strongly
suggest that the desired [2.1.1]orthocyclophane structures
have been obtained.
This strategy was expected to be applicable to the prep-
aration of [2.1.1]orthocyclophanes 2. However, NaÐon-H
catalyzed
cyclibenzylation
of
2,2@-bis(hydroxymethyl)-
diphenylethanes with benzene did not a†ord the desired inter-
molecular cyclibenzylated products 2; instead only a mixture
of 10,11-dihydro-5H-dibenzo[a,d]cycloheptene and 1-benzyl-
10,11-dihydro-5H-dibenzo[a,d]cycloheptene was obtained in
quantitative yields via FriedelÈCrafts intramolecular cycli-
benzylation.13 Consequently, the benzene molecule must not
have been directly incorporated in the cyclic system as an
ortho-phenylene unit in the case of diphenylethane derivatives.
Therefore, we have prepared [2.1.1]orthocyclophanes 2
from 2-bromotoluene 3a and 2-bromo-4-tert-butyltoluene 3b
by using the desulfurization method14 as shown in Schemes 1
and 2. 2-Methoxymethylbromobenzene 5a was prepared by
reaction of 2-bromotoluene 3a with N-bromosuccinimide
(NBS) in the presence of benzoyl peroxide, followed by treat-
ment of the resulting product, 2-bromobenzyl bromide 4a,
with sodium methoxide in reÑuxing methanol for 12 h. The
cross coupling reaction15 of 2-methoxymethylphenyl-
magnesium bromide with o-xylene dibromide was carried out
in the presence of cuprous bromide as catalyst in a mixture of
hexamethylphosphoric triamide (HMPA) and tetrahydrofuran
at reÑux temperature, to give the desired 1,2-bis(2-methoxy-
methylbenzyl)benzene 6a in 61% yield. 1,2-Bis(2-bromo-
methylbenzyl)benzene 7a was prepared in 83% yield by
bromination of 6a with 48% HBr under reÑux. Similarly, 1,2-
bis(2-bromomethyl-5-tert-butylbenzyl)benzene 7b was pre-
pared from 2-bromo-4-tert-butyltoluene, as shown in Scheme
1.
Conformational studies in solution
The 1H-NMR spectrum (Fig. 3) of [2.1.1]orthocyclophane 2a
in CS ÈCDCl (3 : 1) below [60 ¡C shows the methylene
2
3
protons as two sets of doublets at d 3.70, 3.83 and 4.63, 4.92
(each 1 H, J \ 13.8 Hz) and as a set of doublets at d 2.96, 3.16
(each 2 H, J \ 13.8 Hz). It was also found that the CH CH
2
2
methylene protons were observed as four multiplet peaks at d
1.97È3.15 and as a set of doublets at d 3.36, 3.58 (each 2 H,
J \ 13.0 Hz). On the basis of these data it may be inferred
that 2a at this temperature exists as a mixture of syn-crown
and anti-saddle conformers in a ratio of 35 : 65. Thus, the
signals for the bridged methylene protons of the syn-crown
conformer correspond to the set of doublets at d 2.96, 3.16 and
those at d 3.36, 3.58, which strongly suggests the C symmetri-
2
cal structure of syn-crown-2a but not an unsymmetric syn-
saddle conformation (C symmetry). In contrast, the
1
remaining signals for the bridged methylene protons are
assigned as due to the anti-saddle conformer, anti-saddle-2a,
which adopts an unsymmetric structure (C symmetry).
1
However, as the temperature of the solution of 2a in
CS ÈCDCl is increased, the individual peaks of the benzyl
2
3
protons merge and eventually a pair of single peaks is
observed above [20 ¡C. A similar phenomenon was observed
for the tert-butyl derivative 2b, with the ratio of syn-crown to
anti-saddle conformer being 20 : 80. Also, the tert-butyl
protons of syn-crown-2b were observed at higher Ðeld, d 1.10,
The cyclization of 7a,b has been carried out under condi-
tions of high dilution and in ethanolic Na S to a†ord the cor-
2
responding 2-thia[3.1.1]orthocyclophanes 8a,b in 47% and
Scheme 1
Scheme 2
New J. Chem., 2001, 25, 434È439
435

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Fig. 4 X-Ray crystal structure of [2.1.1]orthocyclophane 2a with
thermal vibration ellipsoids shown at the 50% probability level.
Hydrogen atoms are omitted for clarity.
numbering. Compound 2a crystallizes in the triclinic space
group P1 (No. 2) and has one independent molecule (Z \ 2) in
the equivalent position. The bond angles C(8)ÈC(9)ÈC(10) and
C(15)ÈC(16)ÈC(17) over one methylene group are 112.8(1) and
113.8(1)¡, respectively. Although these values are slightly
smaller than the angles C(1)ÈC(2)ÈC(3) and C(2)ÈC(1)ÈC(22)
[115.2(1) and 115.6(1)¡] over two methylene groups, the
carbonÈcarbon bond distances have reasonable values,
1.504(2)È1.519(2) A, and there is no signiÐcant distortion in
the three aromatic rings of the molecule.
The dihedral angles between the internal ten-membered
ring, deÐned by C(1)ÈC(2)ÈC(3)ÈC(8)ÈC(9)ÈC(10)ÈC(15)È
C(16)ÈC(17)ÈC(22), and the three aromatic rings, C(3)ÈC(4)È
C(5)ÈC(6)ÈC(7)ÈC(8), C(10)ÈC(11)ÈC(12)ÈC(13)ÈC(14)ÈC(15)
and C(17)ÈC(18)ÈC(19)ÈC(20)ÈC(21)ÈC(22), are 54.97(4),
37.02(6) and 50.03(4)¡, respectively. This X-ray crystallography
clearly reveals that compound 2a adopts the anti-saddle con-
formation in which one benzene is present between two aro-
matic rings that are forced towards each other (as predicted
from the 1H NMR data).
Fig. 3 Partial 1H-NMR spectrum of 2a at [60 ¡C (CDCl ÈCS \
3
2
1 : 3). The open circles indicate the methylene protons for the anti-
saddle conformer and Ðlled circles indicate the methylene protons for
the syn-crown conformer.
in comparison with those of anti-saddle-2b (d 1.31) due to the
strong shielding e†ect of the benzene ring.14,18 These results
seem to indicate that the bulky tert-butyl groups in 2b play an
important role in Ðxing the conformation. Thus, the bulkiness
of the tert-butyl groups might inhibit the population of the
syn-conformer. Accordingly, the amount of anti-conformer is
found to increase on introduction of tert-butyl groups at the 6
and 19 positions on the benzene ring.
PM3 calculations show that the syn-saddle confomer has
Conclusions
the highest energy, H \ 68.41 kcal mol~1, then the syn-crown
f
We have prepared the [2.1.1]orthocyclophane 2a from 4-tert-
butyltoluene by using the desulfurization method. An inter-
esting result was obtained concerning the conformation of the
[2.1.1]orthocyclophanes 2, which exist as a mixture of anti-
saddle and syn-crown conformers due to the e†ects of the eth-
ylene bridge, the di†erence between these compounds and the
[1.1.1]orthocyclophanes. Further studies on the chemical
properties of [2.1.1]orthocyclophanes 2 are now in progress.
conformer, H \ 62.26 kcal mol~1, with the anti-saddle con-
f
former being lowest in energy H \ 58.35 kcal mol~1. The
higher energy of the syn conformers could be attributable to
f
the fact that the 1,2-diarylethane moiety in the syn-saddle and
syn-crown conformers is eclipsed, whereas that of the anti-
saddle conformer is staggered. These Ðndings are consistent
with the 1H NMR data showing that the anti-saddle and syn-
crown conformers equilibrate.
In the case of calix[4]arenes ([1 ]metacyclophanes),19 *d
4
between H
and H
in the ArCH Ar methylene moiety
Experimental
exo
endo
2
serves as a measure of the ““ÑatteningÏÏ of each phenyl unit:
*d is generally 0.9 ppm for a system in the regular cone con-
formation and in the ““ÑattenedÏÏ conformation *d is signiÐ-
All melting points (Yanagimoto MP-S1) are uncorrected.
Proton nuclear magnetic resonance (1H NMR) spectra were
recorded on a Nippon Denshi JEOL FT-270 spectrometer.
Chemical shifts are reported as d values relative to internal
cantly decreased. Therefore, *d of the ArCH Ar methylene
2
protons in syn-crown-2 might have almost the same value
as that for 10,15-dihydro-5H-tribenzo[a,d,g]cyclononene,
*d \ 1.15, whereas that for the syn-crown conformer has
quite a di†erent value: 0.22 ppm for syn-crown-2a and 0.30
ppm for syn-crown-2b. The large decrease of *d for the
Me Si. Mass spectra were obtained on a Nippon Denshi
4
JMS-01SA-2 mass spectrometer at an ionization energy of 70
eV; m/z values reported include the parent ion peak. Infrared
(IR) spectra were obtained on a Nippon Denshi JIR-AQ2OM
spectrophotometer as KBr disks. Elemental analyses were per-
formed with a Yanaco MT-5. GLC analyses were performed
on a Shimadzu GC-14A gas chromatograph, silicone OV-1 2
m column; programmed temperature rise of 12 ¡C min~1;
nitrogen carrier gas at 25 mL min~1.
ArCH Ar methylene protons in 2 implies that one phenyl ring
2
of 2 becomes Ñattened to reduce the steric crowding between
the two adjacent aromatic protons in the 14 and 18 positions.
X-Ray crystallography
Single colorless crystals of the [2.1.1]orthocyclophane 2a suit-
able for X-ray crystallography were obtained by re-
crystallization from 1 : 1 methanolÈchloroform. A perspective
ORTEP drawing of 2a is illustrated in Fig. 4, with the atom
Syntheses
The preparation of 2-bromo-4-tert-butyltoluene (3b) has been
previously described.15
436
New J. Chem., 2001, 25, 434È439

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2-Bromo-4-tert-butylbenzyl bromide, 4b.
A
mixture of
1,2-Bis(2-bromomethylbenzyl)benzene, 7a. Compound 7a
was synthesized in the same manner as described above for 7b
and obtained in 83% yield as colorless prisms (hexane), mp
4-tert-butyl-2-bromotoluene 3b15 (8 g, 35.2 mmol), N-
bromosuccinimide (6.65 g, 37.4 mmol), benzoyl peroxide (100
mg, 0.376 mmol) and carbon tetrachloride (300 mL) was
reÑuxed for 12 h and the cooled reaction mixture was washed
with aqueous NaOH and water, dried over Na SO , and con-
110È112 ¡C. l /(KBr)/cm~1: 2965, 2870, 1491, 1453, 1218,
max
757, 742, 722, 607; d (CDCl ): 4.10 (4 H, s), 4.39 (4 H, s),
H
3
6.92È7.00 (4 H, m), 7.16È7.22 (6 H, m), 7.31È7.35 (2 H, m); m/z:
2
4
centrated. The residue was distilled under reduced pressure to
give 4b (7.27 g, 67.4%) as a colorless liquid, bp 119È121 ¡C (3
mmHg). d (CDCl ): 1.27 (9 H, s), 4.56 (2 H, s), 7.28 (1 H, dd,
442 (M`), 444, 446. Anal. calc. for C
4.54%. Found: C 59.55, H 4.69%.
H
Br : C 59.49, H
22 20
2
H
3
7,20-Di-tert-butyl-2-thia[3.1.1]orthocyclophane, 8b. A solu-
tion of 7b (900 mg, 1.62 mmol) in ethanol (40 mL) and
benzene (10 mL) and a solution of Na S É 9H O (2.0 g, 8.33
J 1.8, 7.9), 7.35 (1 H, d, J 7.9), 7.96 (1 H, d, J 1.8 Hz); m/z: 304,
306, 308 (M`). Anal. calc. for C
Found: C, 42.96; H, 4.50%.
H
Br : C, 43.17; H, 4.61%.
11 14
2
2
2
mmol) in ethanol (40 mL) and water (8 mL) were added
separately, but simultaneously, from two Hershberg funnels to
boiling ethanol (4 L). When addition was complete (21 h), the
mixture was reÑuxed for 16 h with stirring. Then the reaction
mixture was concentrated and the residue extracted with
CH Cl . The CH Cl extract was washed with water, dried
2-Bromo-4-tert-butylmethoxymethylbenzene, 5b. To a solu-
tion of sodium (1.53 g) in absolute methyl alcohol (60 mL) was
added a solution of 4b (16.0 g, 52.3 mmol) in methyl alcohol
(25 mL), and the mixture was reÑuxed for 12 h. Upon cooling,
it was diluted with water, acidiÐed with acetic acid, and
product was extracted with CH Cl . The CH Cl solution
2
2
2 2
over Na SO , and concentrated. The residue was chromato-
2
4
2
2
2 2
graphed over silica gel (Wako C-300) with hexaneÈbenzene,
1 : 1, as eluents to give a colorless solid. Recrystallization from
hexane a†orded 312 mg (45%) of 8b as colorless prisms, mp
251È253 ¡C. l
max
1453, 1431, 1400, 838, 749; d (CDCl ): 1.14 (18 H, s), 3.55 (4
H, s), 3.57 (4 H, s), 6.80 (2 H, d, J 8.1), 7.22È7.29 (6 H, m), 7.59
was washed with water, dried over Na SO , and concen-
2
4
trated. The residue was distilled under reduced pressure to
give 11.4 g (85%) of 5b as a colorless liquid, bp 124È125 ¡C (4
(KBr)/cm~1: 2962, 2904, 2865, 1498, 1487,
mmHg). l (NaCl)/cm~1: 2965, 2870, 2820, 1479, 1463, 1375,
max
1364, 1274, 1199, 1167, 1112, 1096, 875; d (CDCl ): 1.29 (9
H
3
H
3
H, s), 3.39 (3 H, s), 4.42 (2 H, s), 7.28 (1 H, dd, J 2.0, 7.9), 7.35
(1 H, d, J 7.9), 7.96 (1 H, d, J 2.0 Hz); m/z: 256, 258 (M`).
(2 H, d, J 8.1 Hz); m/z: 428 (M`). Anal. calc. for C
84.06; H, 8.46%. Found: C, 83.99; H, 8.53%.
H
S: C,
30 36
Anal. calc. for C
56.26; H, 6.76%.
H
BrO: C, 56.05; H, 6.66%. Found: C,
12 17
2-Thia[3.1.1]orthocyclophane, 8a. Compound 8a was syn-
thesized in the same manner as described above for 8b and
obtained in 47% yield as colorless prisms (hexaneÈbenzene,
1,2-Bis(5-tert-butyl-2-methoxymethylbenzyl)benzene, 6b. To
a mixture of Mg (1.7 g), tetrahydrofuran (5 mL), and a small
amount of iodine was added a solution of 5b (9.0 g, 35 mmol)
in tetrahydrofuran (25 mL) and the mixture reÑuxed for 12 h.
This Grignard reagent was added to a solution of o-xylene
dibromide (3.96 g, 15 mmol) and CuBr (0.5 g) in HMPA (4
mL) and reÑuxed for 24 h. After the reaction mixture was
1 : 1); mp 263È267 ¡C. l
(KBr)/cm~1: 2962, 1485, 1450,
max
1430, 1081, 1043, 747, 733, 704, 621; d (CDCl ): 3.58 (4 H, s),
H
3
3.59 (4 H, s), 6.78 (2 H, d, J 7.8), 7.03È7.31 (8 H, m), 7.69 (2 H,
d, J 7.8 Hz); m/z: 316 (M`). Anal. calc. for C
83.50; H, 6.37%. Found: C, 83.31; H, 6.22%.
H
S: C,
22 20
7,20-Di-tert-butyl-2-thia[3.1.1]orthocyclophane 2,2-dioxide,
9b. To a solution of 8b (196 mg, 0.457 mmol) in CH Cl (20
cooled to room temperature, it was poured into cold NH Cl
4
solution and extracted with CH Cl . The CH Cl solution
2
2
2
2
2 2
mL) was added m-chloroperbenzoic acid (240 mg, 1.39 mmol).
was washed with water, dried over Na SO , and concen-
2
4
After the reaction mixture had been stirred at room tem-
trated. The residue was chromatographed over silica gel
(Wako C-300) using hexaneÈbenzene, 1 : 1, as eluents to give
3.23 g (47%) of 6b as a colorless oil. d (CDCl ): 1.25 (18 H, s),
3.27 (6 H, s), 4.02 (4 H, s), 4.29 (4 H, s), 6.86È6.89 (2 H, m),
7.03È7.14 (4 H, m), 7.25È7.29 (4 H, m); m/z: 458 (M`). Anal.
perature for 24 h, it was washed with 10% NaHCO aqueous
3
solution and brine, dried over Na SO , and concentrated.
2
4
H
3
The residue was chromatographed over silica gel (Wako
C-300) with hexaneÈbenzene, 1 : 1, as an eluent to give a
colorless solid. Recrystallization from hexane a†orded 212 mg
calc. for C
9.15%.
H
O : C, 83.79; H, 9.23%. Found: C, 83.36; H,
32 42
2
(100%) of 9b as colorless prisms, mp [300 ¡C. l
(KBr)/
max
cm~1: 2962, 2915, 1318, 1308, 1122, 1113, 870, 584; d
H
(CDCl ): 1.13 (18 H, s), 3.52 (4 H, br s), 3.85È4.50 (4 H, br s),
1,2-Bis(2-methoxymethylbenzyl)benzene, 6a. Compound 6a
was synthesized in the same manner as described above for 6b
and obtained in 61% yield as a colorless oil. d (CDCl ): 3.27
3
6.85 (2 H, d, J 8.3 Hz), 7.26È7.38 (6 H, m), 7.75 (2 H, d, J 8.3
Hz); m/z: 460 (M`). Anal. calc. for C
7.88%. Found: C, 78.13; H, 7.78%.
H
O S: C, 78.22; H,
30 36
2
H
3
(6 H, s), 3.98 (4 H, s), 4.32 (4 H, s), 6.91È7.37 (12 H, m); m/z:
346 (M`). Anal. calc. for C
Found: C, 83.06; H, 7.35%.
H
O : C, 83.28; H, 7.56%.
2-Thia[3.1.1]orthocyclophane 2,2-dioxide, 9a. Compound 9a
was synthesized in the same manner as described above for 9b
and obtained in quantitative yield as colorless prisms, mp
24 26
2
1,2-Bis(2-bromomethyl-5-tert-butylbenzyl)benzene, 7b.
A
[300 ¡C. l
(KBr)/cm~1: 2962, 1490, 1450, 1410, 1317,
max
mixture of 6b (566 mg, 1.23 mmol) and 48% HBr (20 mL) was
reÑuxed for 24 h and the reaction mixture was cooled to room
temperature. This mixture was poured into a large amount of
ice water, and extracted with CH Cl (30 mL ] 2). The
1308, 1297, 1247, 1119, 855, 841; d (CDCl ): 3.56 (4 H, br s),
H
3
3.82È4.60 (4 H, br s), 6.84 (2 H, d, J 7.8), 7.18È7.40 (8 H, m),
7.85 (2 H, d, J 7.8 Hz); m/z: 348 (M`). Anal. calc. for
C
H
O S: C, 75.83; H, 5.79%. Found: C, 75.70; H, 5.64%.
2
2
22 20
2
CH Cl solution was washed with water, dried over Na SO ,
2
2
2
4
and concentrated. The residue was chromatographed over
silica gel (Wako C-300) with hexaneÈbenzene, 1 : 1, as eluents
to give a colorless solid. Recrystallization from hexane a†ord-
6,19-Di-tert-butyl[2.1.1]orthocyclophane, 2b. The sulfone 9b
(150 mg, 0.326 mmol) was pyrolyzed at 500 ¡C under reduced
pressure at 1 mmHg as reported previously.16 The sublimed
product was collected and chromatographed on silica gel with
hexane as an eluent to give a colorless solid. Recrystallization
from hexane a†orded 118 mg (91%) of 2b as colorless prisms,
mp 166È168 ¡C. d (CDCl ; 27 ¡C): 1.33 (18 H, s, tBu), 2.67 (4
ed 376 mg (55%) of 7b as colorless prisms, mp 114 ¡C. l
max
(KBr)/cm~1: 2965, 1604, 1474, 1450, 1362, 1231, 1202, 1186,
827, 753, 631, 618; d (CDCl ): 1.25 (18 H, s), 4.15 (4 H, s),
H
3
4.39 (4 H, s), 6.88È6.92 (2 H, m), 7.03 (4 H, m), 7.23È7.30 (4 H,
H
3
m); m/z: 554, 556, 558 (M`). Anal. calc. for C
64.76; H, 6.52%. Found: C, 64.81; H, 6.48%.
H
Br O: C,
H, br s, CH CH ), 4.14 (4 H, br s, CH ), 7.03È7.18 (4 H, m,
30 36
2
2
2
2
ArH), 7.20È7.36 (6 H, m); d (CS ÈCDCl , 3 : 1; [80 ¡C):
H
2
3
New J. Chem., 2001, 25, 434È439
437

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(anti-2b) 1.31 (18 H, s, tBu), 1.86È1.96 (1 H, m, CH CH ), 2.08È
measured with uÈ2h scans (u scan width \ 0.8 ] 0.14 tan h);
Ni-Ðltered Cu-Ka radiation (j \ 1.541 84 A) was used. The
X-ray analysis was performed with the MolEN program
package20 and the structure was solved uneventfully by direct
methods (SIR88).21 The reÐnement was by full-matrix least-
squares.
CCDC reference number 440/248. See http://www.rsc.org/
suppdata/nj/b0/b008258i/ for crystallographic Ðles in .cif
format.
2
2
2.22 (1 H, m, CH CH ), 2.48È2.60 (1 H, m, CH CH ), 3.12È
2
2
2
2
3.22 (1 H, m, CH CH ), 3.68 (1 H, d, J 13.8, CH ), 3.83 (1 H,
2
2
2
d, J 13.8, CH ), 4.63 (1 H, d, J 13.8, CH ), 3.92 (1 H, d, J 13.8,
2
2
CH ), 6.8È7.4 (10 H, m, ArH); (syn-2b) 1.10 (18 H, s, tBu), 2.88
2
(2 H, d, J 13.0, CH CH ), 3.10 (2 H, d, J 13.0, CH CH ), 3.34
2
2
2
2
2
(2 H, d, J 13.8, CH ), 3.64 (2 H, d, J 13.8 Hz, CH ), 6.8È7.4 (10
2
H, m, ArH); m/z: 396 (M`). Anal. calc. for C
H
: C, 90.85;
30 36
H, 9.15%. Found: C, 90.66; H, 9.08%.
References
[2.1.1]Orthocyclophane, 2a. Compound 2a was synthesized
in the same manner as described above for 2b and obtained in
1
2
T. Yamato, K. Noda and K. Tanaka, J. Chem. Res. (M), in press.
(a) A. Collet, T etrahedron, 1987, 43, 5725; (b) T. Sato and K.
Uno, J. Chem. Soc., Chem. Commun., 1972, 579; (c) T. Sato and K.
Uno, J. Chem Soc., Perkin T rans. 1, 1973, 895.
(a) S. Cerrini, E. Giglio, F. Mazza and N. V. Pavel, Acta Crystal-
logr., Sect. B, 1979, 35, 2605; (b) J. A. Hyatt, E. N. Duesler, D. Y.
Curtin and I. C. Paul, J. Org. Chem., 1980, 45, 5074.
A. Collet and J. Gabard, J. Org. Chem., 1980, 45, 5400.
(a) R. C. Cookson, B. Halton and I. D. R. Stevens, J. Chem. Soc.,
Perkin T rans. 1, 1968, 767; (b) J. E. Baldwin and D. P. Kelly, J.
Chem. Soc., Chem. Commun., 1968, 1664.
(a) J. F. Manville and G. E. Troughton, J. Org. Chem., 1973, 38,
4278; (b) J. Canceil, J. Gabard and A. Collet, J. Chem. Soc., Chem.
Commun., 1983, 122; (c) G. Combaut, J.-M. Chantraine, J. Teste,
J. Soulier and K.-W. Glombitza, T etrahedron L ett., 1978, 1699.
(a) J. Bosch, J. Canals and R. Granados, Anal. Quim., 1976, 72,
709; (b) T. Yamato, N. Sakaue, L. K. Doamekpor and M.
Tashiro, J. Chem. Res. (S), 1994, 176.
97% yield as colorless prisms (hexane), mp 174È176 ¡C. t
max
(KBr)/cm~1: 2962, 1490, 1453, 1434, 1086, 771, 757, 740, 726,
621; d (CDCl ): 2.85 (4 H, br s, CH CH ), 4.00 (4 H, br s,
3
H
3
2
2
CH ), 7.15È7.25 (12 H, m, ArH); d (CS ÈCDCl , 3 : 1
2
H
2
3
[80 ¡C): (anti-2a) 1.97È2.06 (1 H, m, CH CH ), 2.12È2.24 (1
H, m, CH CH ), 2.51È2.63 (1 H, m, CH CH ), 3.03È3.15 (1 H,
2
2
4
5
2
2
2
2
2
m, CH CH ), 3.70 (1 H, d, J 13.8, CH ), 3.83 (1 H, d, J 13.8,
2
2
CH ), 4.63 (1 H, d, J 13.8, CH ), 4.92 (1 H, d, J 13.8, CH ),
2
2
2
6.8È7.43 (12 H, m, ArH); (syn-2a) 2.96 (2 H, d, J 12.0,
CH CH ), 3.16 (2 H, d, J 12.0, CH CH ), 3.36 (2 H, d, J 13.8,
CH ), 3.58 (2 H, d, J 13.8 Hz, CH ), 6.8È7.43 (12 H, m, ArH);
m/z: 284 (M`). Anal. calc. for C
6
2
2
2
2
2
2
H
: C, 92.91; H, 7.09%.
22 20
7
8
Found: C, 93.00; H, 7.24%.
AlCl –MeNO catalyzed trans-tert-butylation of 2b in benzene
3
2
(a) B. H. Smith, Bridged Aromatic Compounds, Academic Press,
New York, USA, 1964; (b) D. J. Cram and J. M. Cram, Acc.
Chem. Res., 1971, 4, 204; (c) P. M. Keehn and S. M. Rosenfeld,
Cyclophanes, Academic Press, New York, USA, 1983.
(a) C. D. Gutsche, Acc. Chem. Res., 1983, 16, 161; (b) A. Collet,
T etrahedron, 1987, 5725.
To a solution of 2b (100 mg, 0.25 mmol) in benzene (5 mL)
was added a solution of AlCl (80 mg, 0.6 mmol) in MeNO
3
2
(0.15 mL) at room temperature. After stirring the reaction
mixture at room temperature for 2 h, it was poured into ice
water (30 mL) and extracted with benzene (10 mL ] 2). The
combined extracts were washed with water (10 mL ] 2), dried
(Na SO ) and concentrated. The residue was chromato-
9
10 (a) A. G. S. Hogberg, J. Am. Chem. Soc., 1980, 102, 6046; (b) J. D.
White and B. D. Gesner, T etrahedron L ett., 1968, 1591; (c) T. Wu
and J. R. Speas, J. Org. Chem., 1987, 52, 1330.
2
4
graphed over silica gel using hexane as eluent to give 50 mg
(70%) of 2a as colorless prisms. The formation of tert-
butylbenzene 10 was conÐrmed by GLC.
11 T. Sato and K. Uno, J. Chem Soc., Perkin T rans. 1, 1973, 895.
12 (a) T. Yamato, C. Hideshima, G. K. S. Prakash and G. A. Olah,
J. Org. Chem., 1991, 56, 2089; (b) T. Yamato, N. Sakaue, T. Fur-
usawa, M. Tashiro, G. K. S. Prakash and G. A. Olah, J. Chem.
Res. (S), 1991, 242; T. Yamato, N. Sakaue, T. Furusawa, M.
Tashiro, G. K. S. Prakash and G. A. Olah, J. Chem. Res. (M),
1991, 2414; (c) T. Yamato, K. Fujita, N. Shinoda, K. Noda, Y.
Nagano, T. Arimura and M. Tashiro, Res. Chem. Intermed., 1996,
22, 871; (d) T. Yamato, J. Synth. Org. Chem. Jpn., 1995, 53, 487.
13 T. Yamato, N. Sakaue, M. Komine and Y. Nagano, J. Chem. Res.
(S), 1997, 246; T. Yamato, N. Sakaue, M. Komine and Y.
Nagano, J. Chem. Res. (M), 1997, 1537.
14 (a) V. Boekelheide, T op. Curr. Chem., 1983, 113, 87; (b) F. Vogtle,
Cyclophane Chemistry, Wiley, Chichester, UK, 1993; (c) R. H.
Mitchell and V. Boekelheide, T etrahedron L ett., 1970, 1197; (d)
R. H. Mitchell and V. Boekelheide, J. Chem. Soc., Chem.
Commun., 1970, 1555; (e) W. Anker, G. W. Bushnell and R. H.
Mitchell, Can. J. Chem., 1979, 57, 3080; ( f ) R. H. Mitchell, R. J.
Carruther, L. Mazuch and T. W. Dingle, J. Am. Chem. Soc., 1982,
104, 2544; (g) R. H. Mitchell and V. Boekelheide, J. Am. Chem.
Soc., 1974, 96, 1547.
PM3 calculations
PM3 calculations and energy minimizations were carried out
with the Wavefunction MacSpartan Plus (V 1.2.2) package
software using an Apple Macintosh G4/400.
X-Ray crystallography
Crystallographic data for 2a are given in Table 1. The unit cell
constants were derived from least-squares analysis of the set-
tings, on an Enraf-Nonius CAD4 FR 586 di†ractometer, for
25 reÑections in the range 34.96¡ \ h \ 36.83¡. The intensities
of all independent reÑections with 6.02¡ \ 2h \ 149.76¡ were
Table
1 Crystallographic data and data collection details for
[2.1.1]orthocyclophane 2a
15 (a) T. Yamato, J. Matsumoto, S. Ide, K. Tokuhisa, K. Suehiro
and M. Tashiro, J. Org. Chem., 1992, 57, 5243; (b) T. Yamato, J.
Matsumoto, K. Tokuhisa, M. Kajihara, K. Suehiro and M.
Tashiro, Chem. Ber., 1992, 125, 2443.
16 (a) M. Tashiro and T. Yamato, Synthesis, 1981, 435; (b) M.
Tashiro and T. Yamato, J. Am. Chem. Soc., 1982, 104, 3701; (c)
M. Tashiro, K. Koya and T. Yamato, J. Am. Chem. Soc., 1982,
104, 3707; (d) T. Yamato, L. K. Doamekpor, K. Koizumi, K.
Kishi, M. Haraguchi and M. Tashiro, L iebigs Ann., 1995, 1259;
(e) T. Yamato, Y. Saruwatari and M. Yasumatsu, J. Chem. Soc.,
Perkin T rans. 1, 1997, 1725.
17 (a) M. Tashiro and T. Yamato, J. Org. Chem., 1981, 46, 1543; (b)
M. Tashiro and T. Yamato, J. Org. Chem., 1985, 50, 2939; (c) T.
Yamato, J. Matsumoto, K. Tokuhisa, K. Tsuji, K. Suehiro and
M. Tashiro, J. Chem. Soc., Perkin T rans. 1, 1992, 2675; (d) T.
Yamato, A. Miyazawa and M. Tashiro, Chem. Ber., 1993, 126,
2505; (e) T. Yamato, A. Miyazawa and M. Tashiro, J. Chem. Soc.,
Perkin T rans. 1, 1993, 3127; ( f ) T. Yamato, J. Matsumoto and K.
Fujita, J. Chem. Soc., Perkin T rans. 1, 1998, 123.
Formula
FW
Crystal system
Space group
C
H
22 20
284.40
Triclinic
P1 (no. 2)
10.2590(5)
14.7368(7)
5.1617(4)
93.601(5)
111.643(5)
85.992(4)
772.88(8)
2
298
4.82
0.046
0.081
3556
3187
a/A
b/A
c/A
a/¡
b/¡
c/¡
U/A
Ž
3
Z
T /K
k/cm~1
R
R a
w
No. of reÑections
Unique reÑections
18 (a) M. Tashiro and T. Yamato, J. Org. Chem., 1981, 46, 4556; (b)
M. Tashiro and T. Yamato, J. Org. Chem., 1983, 48, 1461.
a u \ 4(F )2/[(pI )2 ] 0.0016(F )4].
o
o
o
438
New J. Chem., 2001, 25, 434È439

View Article Online
19 (a) C. D. Gutsche, Calixarenes, Royal Society of Chemistry, Cam-
bridge, UK, 1989; (b) J. Vicens and V. Bohmer, Calixarenes: A
V ersatile Class of Macrocyclic Compounds, Kluwer Academic
Publishers, Cambridge, UK, 1990; (c) V. Bohmer, Angew. Chem.,
Int. Ed. Engl., 1995, 34, 713; (d) K. Iwamoto and S. Shinkai, J.
Org. Chem., 1992, 57, 7066.
20 MolEN, An Interactive Structure Solution Procedure, Enraf-
Nonius, Delft, The Netherlands, 1990.
21 M. C. Burla, M. Camalli, G. Cascarano, C. Giacovazzo, G. Pol-
idori, R. Spagna and D. Viterbo, J. Appl. Crystallogr., 1989, 22,
389.
New J. Chem., 2001, 25, 434È439
439