Synthesis, structure, and transannular π-π interaction of three- and four-layered [3.3]paracyclophanes

Article abstract of DOI:10.1021/jo8003309

(Figure Presented) The synthesis of three- and four-layered [3.3]paracyclophanes ([3.3]PCPs) 3-5 has been accomplished by utilizing the (p-ethylbenzenesulfonyl)methyl isocyanide (EbsMIC) method. The structures of the three- to four-layered [3.3]PCPs 3-5 and their diones 8, 10, and 11 have been elucidated based on the ¹H NMR spectra and finally by X-ray structural analysis. In the three-layered [3.3]PCP-dione 8, the trimethylene bridges of the [3.3]PCP unit assume a chair conformation similar to that of 2, while the [3.3]PCP-2,11-dione unit assumes a boat conformation different from that of [3.3]PCP-dione 1 with a chair conformation. On the other hand, the two [3.3]PCP units in three-layered [3.3]PCP 3 both assume a boat conformation. In the four-layered [3.3]PCP-dione 10, the two outer [3.3]PCP units assume a boat conformation while the inner dione unit has a chair conformation. The trimethylene bridges in the four-layered [3.3]PCP 4 are highly disordered even at -150°C. All the outer benzene rings are distorted into a boat form while the inner ones are distorted into a twist form. In the electronic spectra, bathochromic shift and hyperchromic effect are observed, but the magnitude decreases with an increase in the number of layers and the spectra become structureless. In the charge-transfer (CT) bands of the three- to four-layered [3.3]PCPs 3-5 with tetracyanoethylene (TCNE), two absorption maxima (λ_max) are observed. The effect of an increase in the layers becomes significant, and the changes in the longest wavelength λ_max values from two to three and three to four are ca. 60 and 50 nm, respectively. By comparison of the stereoisomeric four-layered [3.3]PCPs 4 (meso) and 5 (racemic), the helical arrangement of the trimethylene bridges of 5 shows a more efficient transannular π-electronic interaction. In the three- to four-layered [3.3]PCP-diones, a magnitude of the CT interaction almost comparable to that of [3.3]PCP 2 was observed, and this indicates that the -CH₂COCH₂- bridges inhibit the CT interaction and that this tendency is supported by the calculated HOMO energy levels and observed oxidation potentials. Three- and four-layered [3.3]PCPs 3-5 show reversible redox processes, and 4 and 5 show an electron-donating ability almost comparable to that of [3₆]CP. Very good correlation between the λλ_max of the CT bands with TCNE and the oxidation potentials is observed.

Full text of DOI:10.1021/jo8003309

Synthesis, Structure, and Transannular π-π Interaction of Three-
and Four-Layered [3.3]Paracyclophanes1
Masahiko Shibahara,*,† Motonori Watanabe,‡,§ Tetsuo Iwanaga,| Taisuke Matsumoto,‡
Keiko Ideta,‡ and Teruo Shinmyozu‡
Department of Chemistry, Faculty of Education and Welfare Science,
Oita UniVersity, 700 Dannoharu, Oita 870-1192, Japan, Institute for Materials Chemistry and Engineering
(IMCE) and Department of Molecular Chemistry, Graduate School of Sciences, Kyushu UniVersity,
6-10-1 Hakozaki, Fukuoka 812-8581, Japan, and Department of Chemistry, Faculty of Science,
Okayama UniVersity of Science, 1-1 Ridaicho, Okayama 700-0005, Japan
ReceiVed February 8, 2008
The synthesis of three- and four-layered [3.3]paracyclophanes ([3.3]PCPs) 3-5 has been accomplished by
utilizing the (p-ethylbenzenesulfonyl)methyl isocyanide (EbsMIC) method. The structures of the three- to
four-layered [3.3]PCPs 3-5 and their diones 8, 10, and 11 have been elucidated based on the 1H NMR spectra
and finally by X-ray structural analysis. In the three-layered [3.3]PCP-dione 8, the trimethylene bridges of the
[3.3]PCP unit assume a chair conformation similar to that of 2, while the [3.3]PCP-2,11-dione unit assumes
a boat conformation different from that of [3.3]PCP-dione 1 with a chair conformation. On the other hand,
the two [3.3]PCP units in three-layered [3.3]PCP 3 both assume a boat conformation. In the four-layered
[3.3]PCP-dione 10, the two outer [3.3]PCP units assume a boat conformation while the inner dione unit has
a chair conformation. The trimethylene bridges in the four-layered [3.3]PCP 4 are highly disordered even at
-150 °C. All the outer benzene rings are distorted into a boat form while the inner ones are distorted into a
twist form. In the electronic spectra, bathochromic shift and hyperchromic effect are observed, but the magnitude
decreases with an increase in the number of layers and the spectra become structureless. In the charge-transfer
(CT) bands of the three- to four-layered [3.3]PCPs 3-5 with tetracyanoethylene (TCNE), two absorption
maxima (λmax) are observed. The effect of an increase in the layers becomes significant, and the changes in
the longest wavelength λmax values from two to three and three to four are ca. 60 and 50 nm, respectively. By
comparison of the stereoisomeric four-layered [3.3]PCPs 4 (meso) and 5 (racemic), the helical arrangement
of the trimethylene bridges of 5 shows a more efficient transannular π-electronic interaction. In the three- to
four-layered [3.3]PCP-diones, a magnitude of the CT interaction almost comparable to that of [3.3]PCP 2
was observed, and this indicates that the -CH2COCH2- bridges inhibit the CT interaction and that this tendency
is supported by the calculated HOMO energy levels and observed oxidation potentials. Three- and four-
layered [3.3]PCPs 3-5 show reversible redox processes, and 4 and 5 show an electron-donating ability almost
comparable to that of [36]CP. Very good correlation between the λmax of the CT bands with TCNE and the
oxidation potentials is observed.
1. Introduction
propriate cyclophane building blocks, i.e., para, meta, and
metapara.2–7 Since the first synthesis of various four-layered
[2.2]PCP8 and three-layered CPs,9 several types of multilayered
[2.2]CPs4–6 were developed by Otsubo et al. and their charac-
teristic chemical and physical properties have been reported.10
Multilayered cyclophanes (CPs) have served as suitable
models for the study of their characteristic structural properties
and transannular π-electronic interaction by choosing the ap-
* To whom correspondence should be addressed. Phone: +81-97-554-7553.
Fax: +81-97-554-7553. mshiba@cc.oita-u.ac.jp
† Oita University.
(1) Multilayered [3.3]cyclophanes, part 3. For parts 1 and 2, see refs 2 and 3.
(2) Shibahara, M.; Watanabe, M.; Iwanaga, T.; Ideta, K.; Shinmyozu, T. J.
Org. Chem. 2007, 72, 2865–2877.
‡ IMCE, Kyushu University.
§ Department of Molecular Chemistry, Kyushu University.
| Okayama University of Science.
(3) Muranaka, A.; Shibahara, M.; Watanabe, M.; Matsumoto, T.; Shinmyozu,
T.; Kobayashi, N. To be submitted for publication.
10.1021/jo8003309 CCC: $40.75
Published on Web 05/23/2008
2008 American Chemical Society
J. Org. Chem. 2008, 73, 4433–4442 4433

Shibahara et al.
FIGURE 1. Multilayered [3.3]PCPs 2-5 and [3.3]PCP-dione 1.
Among the various multilayered [2.2]CPs, paracyclophanes have
chiroptical properties inherent in their helical features, and the
synthesis of optically active multilayered [2.2]PCPs (up to six
layers) was accomplished by Yamamoto et al.7 Although [3.3]PCP
is a better system than [2.2]PCP for investigation of electronic
interaction because of the most appropriate transannular distance
and much less strain of the benzene rings,11 only a limited number
of multilayered [3.3]CPs have been synthesized so far.12–14 Otsubo
et al. reported that three-layered [3.3][3.3]PCP showed the strongest
electron-donating ability among the three-layered [m.m][n.n]PCPs
(m and n ) 2-4).12 Mataka et al. reported the synthesis of up to
four-layered [3.3]orthocyclophanes.14b
In the previous paper, we reported that the electron-donating
ability of the multilayered [3.3]MCPs gradually increases with
an increase in the layers, but the magnitude becomes less signi-
ficant as the number of layers increases.2 The moderate electron-
donating ability of the multilayered [3.3]MCPs compared to that
of the [3n]CPs15 may be ascribed to the tilted overlap of the
benzene rings in the former. Quite interestingly, the anti
geometry of the [3.3]MCP-2,11-dione moiety in the multilayered
[3.3]MCPs serves as an electron insulator, and this suggested
the importance of through-bond interaction for electronic inter-
action. Lately, our collaborators, Muranaka et al., reported the
CD spectral properties and absolute configuration of R-(-)- and
S-(+)-three-layered [3.3]PCPs 3 (Figure 1), and they concluded
that the chiroptical properties of 3 are little affected by the
conformation of the bridge carbon atoms, twisted structure, and
deformation of the benzene rings.3 This interpretation is different
from that for multilayered [2.2]PCP, where distorted benzene
rings are reported to be responsible for the CD spectra.7b
A systematic study on the multilayered [3.3]PCPs may provide
(1) general synthetic methods for multilayered [3.3]PCPs, (2)
further information on the electronic interaction through completely
stacked and less strained benzene rings with appropriate distances,
and (3) absolute configuration and chiroptical properties. We wish
to report here the synthesis, structure, and electronic interaction of
the three- and four-layered [3.3]PCPs 3-5 along with their synthe-
tic intermediate diones 8, 10, and 11.
2. Results and Discussion
Synthesis. In the previous paper, we already reported the
synthesis of three-layered [3.3]PCPs 3.3 We used (p-ethylben-
zenesulfonyl)methyl isocyanide (EbsMIC)16 instead of conven-
tional (p-tolylsulfonyl)methyl isocyanide (TosMIC)16c for im-
provement of the solubility in CH2Cl2 in the critical coupling
reaction.17 The synthetic key intermediates in the synthesis of
multilayered [3.3]PCPs are two-layered bis(bromomethyl) com-
pound 6 (racemic)3 and its EbsMIC adduct 9 (racemic). The
two-layered bromide 6 was coupled with the EbsMIC adduct
7 to give three-layered dione 8 (racemic, 22%, Scheme 1).
The Wolff-Kishner reduction of 8 afforded the three-layered
[3.3]PCP 3 (racemic, 82%),3,12 whose resolution was attained
by HPLC separation with a chiral stationary phase (Daicel
Chemical Industries, Ltd.: Chiralcel OD with 2-propanol).3
A similar coupling of the dibromide 6 (racemic) with its
EbsMIC adduct 9 (racemic) provided the two-isomeric mixture
of 10 (C2h, meso) and 11 (D2, racemic) with the ratio of 1.0:1.4
(10:11) based on the 1H NMR integral ratio (Figure S1,
Supporting Information). The separation of the meso and
racemic isomers was accomplished by the difference in the
solubility in acetonitrile: the less soluble isomer was meso 10
and the readily soluble one was a racemic mixture 11. After
silica gel column chromatography, pure 10 (meso) and 11
(4) (a) Otsubo, T.; Mizogami, S.; Sakata, Y.; Misumi, S. Tetrahedron Lett.
1971, 12, 4803–4806. (b) Otsubo, T.; Mizogami, S.; Sakata, Y.; Misumi, S.
Tetrahedron Lett. 1973, 14, 2457–2460. (c) Otsubo, T.; Mizogami, S.; Sakata,
Y.; Misumi, S. Tetrahedron Lett. 1972, 13, 2927–2930. (d) Otsubo, T.; Mizogami,
S.; Otsubo, I.; Tozuka, Z.; Sakagami, A.; Sakata, Y.; Misumi, S. Bull. Chem.
Soc. Jpn. 1973, 46, 3519–3530.
(5) (a) Kannen, N.; Umemoto, T.; Otsubo, T.; Misumi, S. Tetrahedron Lett.
1973, 14, 4537–4540. (b) Kannen, N.; Otsubo, T.; Sakata, Y.; Misumi, S. Bull.
Chem. Soc. Jpn. 1976, 49, 3307–3313. (c) Kannen, N.; Otsubo, T.; Sakata, Y.;
Misumi, S. Bull. Chem. Soc. Jpn. 1976, 49, 3203–3207. (d) Kannen, N.; Otsubo,
T.; Sakata, Y.; Misumi, S. Bull. Chem. Soc. Jpn. 1976, 49, 3208–3212.
(6) (a) Umemoto, T.; Otsubo, T.; Sakata, Y.; Misumi, S. Tetrahydron Lett.
1973, 14, 593–596. (b) Umemoto, T.; Otsubo, T.; Misumi, S. Tetrahydron Lett.
1974, 15, 1573–1676.
(7) (a) Nakazaki, M.; Yamamoto, K.; Tanaka, S. J. Chem. Soc., Chem.
Commun. 1972, 433. (b) Nakazaki, M.; Yamamoto, K.; Tanaka, S.; Kametani,
H. J. Org. Chem. 1977, 42, 287–291.
(8) (a) Longone, D. T.; Chow, H. S. J. Am. Chem. Soc. 1964, 86, 3898–
3899. (b) Longone, D. T.; Chow, H. S. J. Am. Chem. Soc. 1970, 92, 994–998.
(9) Hubert, A. J. J. Chem. Soc. C. 1967, 13–14.
(10) For reviews, see:(a) Misumi, S.; Otsubo, T. Acc. Chem. Res. 1978, 11,
251–256. (b) Misumi, S. Mem. Inst. Sci. Ind. Res., Osaka UniV. 1976, 33, 53–
71. (c) Misumi, S. In Cyclophanes II; Keehn, P. M., Rosenfeld, S. M., Eds.;
Academic Press: New York, 1983: pp 573-624. (d) Vo¨gtle, F. Cyclophan-
Chemie; B. G. Teubner: Stuttgart, Germany, 1990.
(11) (a) Cram, D. J.; Bauer, R. H. J. Am. Chem. Soc. 1959, 81, 5971–5977.
(b) Sheehan, M.; Cram, D. J. J. Am. Chem. Soc. 1969, 91, 3553–3558.
(12) (a) Otsubo, T.; Kohda, T.; Misumi, S. Tetrahedron Lett. 1978, 19, 2507–
2510. (b) Otsubo, T.; Kohda, T.; Misumi, S. Bull. Chem. Soc. Jpn. 1980, 53,
512–517.
(13) Breidenbach, S.; Ohren, S.; Nieger, M.; Vo¨gtle, F. The proceeding of
the 8th International Symposium on Novel Artomatic Compounds (ISNA-8),
Braunschweike, Germany, July-August, 1995. But no report on the synthesis
of three-layered [3.3]MCP has been published yet.
(16) EbsMIC 11 was synthesized by modified procedures starting from
ethylbenzene: (a) Clarke, H. T.; Babcook, G. S.; Murray, T. F. Organic Syntheses,
2nd ed.; Wiley: New York, 1967; Collect. Vol. I, pp 85-87. (b) Field, L.; Clark,
R. D. Organic Syntheses; Wiley: New York, 1963; Collect. Vol. IV, pp 674-
677. (c) Hoogenboom, B. E.; Oldenziel, O. H.; van Leusen, A. M. Organic
Syntheses; Wiley: New York, 1988; Collect. Vol. VI, pp 987-990.
(17) (a) Possel, O.; van Leusen, A. M. Tetrahedron Lett. 1977, 18, 4229–
4232. (b) Kurosawa, K.; Suenaga, M.; Inazu, T.; Yoshino, T. Tetrahedron Lett.
1982, 23, 5335–5338. (c) Shinmyozu, T.; Hirai, Y.; Inazu, T. J. Org. Chem.
1986, 51, 1551–1555. (d) Sasaki, H.; Kitagawa, T. Chem. Pharm. Bull. 1983,
31, 2868–2878. (e) Breitenbach, J.; Vo¨gtle, F. Synthesis 1992, 41–42. (f) Sentou,
W.; Satou, T.; Yasutake, M.; Lim, C.; Sakamoto, Y.; Itoh, T.; Shinmyozu, T.
Eur. J. Org. Chem. 1999, 1223–1231.
(14) (a) Mataka, S.; Mitoma, Y.; Thiemann, T.; Sawada, T.; Taniguchi, M.;
Kobuchi, M.; Tashiro, M. Tetrahedron 1997, 53, 3015–3026. (b) Mataka, S.;
Shigaki, K.; Sawada, T.; Mitoma, Y.; Taniguchi, M.; Thieman Thies.; Ohga,
K.; Egashira, N. Angew. Chem., Int. Ed. 1998, 37, 2532–2534.
(15) (a) Sakamoto, Y.; Miyoshi, N.; Shinmyozu, T. Angew. Chem., Int. Ed.
Engl. 1996, 35, 549–550. (b) Sakamoto, Y.; Miyoshi, N.; Hirakida, M.;
Kusumoto, S.; Kawase, H.; Rudzinski, J. M.; Shinmyozu, T. J. Am. Chem. Soc.
1996, 118, 12267–12275. (c) Sakamoto, Y.; Shinmyozu, T. Recent Res. DeV.
Pure Appl. Chem. 1998, 2, 372–399.
4434 J. Org. Chem. Vol. 73, No. 12, 2008

Three- and Four-Layered [3.3]Paracyclophanes
SCHEME 1. Synthetic Route to Three- and Four-Layered [3.3]PCPs 3-5
(racemic) were obtained in 12% and 7% yield, respectively.
The isolated yield of 11 was low because of its good solubility
in organic solvents. The modified Wolff-Kishner reduction of
each of the diones afforded four-layered [3.3]PCPs 4 (meso,
72%) and 5 (racemic, 22%), respectively. Resolution of 5
(racemic) by HPLC separation with a chiral stationary phase is
in progress, and their absolute configurations and chiroptical
properties will be reported elsewhere.
1H NMR Spectral Properties. Figure 2 shows the selected
1H NMR data for multilayered [3.3]PCPs and the corresponding
multilayered [2.2]PCPs as references.18 The outer aromatic
protons (Ha and Ha′) of multilayered [3.3]PCPs exhibit slight
upfield shifts as the number of layers increases due to the ring
current effect of the facing benzene rings, but the magnitude is
smaller than that of the corresponding multilayered [2.2]PCPs.
The Hi protons also show similar phenomena. All Ha and Ha′
protons of three- and four-layered [3.3]PCPs appear as double-
doublets (Jortho and Jmeta) due to the influence of the benzylic
protons of the trimethylene bridges at the pseudogeminal
position. The Ha proton undergoes the steric compression effect
of the benzylic protons at the pseudogeminal position and
appears at slightly lower field than the corresponding Ha′ protons.
Similarly, the Hi protons of racemic 5 are slightly deshielded
(∆δ 0.05 ppm) compared to the corresponding protons of meso
4 due to this effect. On the other hand, the steric compression
effect was not observed in the outer aromatic protons (Ha) of
the multilayered [2.2]PCPs because the distance between the
Ha proton and the benzylic protons of the bridge at the
pseudogeminal position lengthens due to the bending of the inner
benzene ring into a boat shape. In the multilayered [3.3]PCP-
diones, the aromatic protons of 8 and the Hi protons of 10 and
11 are slightly deshielded compared to the corresponding protons
of the multilayered [3.3]PCPs. A similar steric compression
effect was observed in the Hi protons of 11 compared to the
corresponding protons of 10.
FIGURE 2. Selected 1H NMR data of multilayered [3.3]PCPs and
multilayered [2.2]PCPs18 in CDCl3.
X-ray Structural Analysis. To examine the structural proper-
ties of the multilayered [3.3]PCPs, we carried out their single-
crystal X-ray structural analyses. The crystal data are summa-
rized in Table S1 (Supporting Information). Figure 3 shows the
molecular structure of three-layered [3.3]PCP-dione 8 (-160
°C). The ORTEP drawing shows that the [3.3]PCP unit assumes
a chair conformation, whereas the [3.3]PCP-dione unit assumes
a boat one (Figure 3A). The three benzene rings are stacked
with the distances of 3.33 Å for the [3.3]PCP-dione unit and
(18) Otsubo, T.; Mizogami, S.; Sakata, Y.; Misumi, S. Bull. Chem. Soc. Jpn.
1973, 46, 3831–3835.
J. Org. Chem. Vol. 73, No. 12, 2008 4435

Shibahara et al.
FIGURE 4. The short contacts of three-layered [3.3]PCP-dione 8. (A)
The crystal-packing diagram along the a-axis. The carbon atoms are
represented as blue (far side) and yellow (this side). (B) Hydrogen bonds
between carbonyl oxygen (O1) and benzylic protons (H24 and H25)
and carbonyl oxygen (O2) and aromatic proton (H10) along the c-axis.
Hydrogen atoms H10, H24, and H25 only are represented for clarity.
FIGURE 3. ORTEP drawing of the molecular structures of three-
layered [3.3]PCP-dione 8 (-160 °C): top (A) and side (B) views.
3.31 Å for the [3.3]PCP unit, and these values are comparable
to those of 1 (3.33 Å)19 and 2 (3.31 Å),20 respectively. The
benzene rings of the [3.3]PCP unit overlap each other, but the
third benzene ring of the dione unit slightly deviates from
complete stacking. The tilt of the benzene rings is 3.4° for the
[3.3]PCP unit, whereas it is 5.0° for the [3.3]PCP-dione unit.
In the crystal-packing diagram of 8 (Figure 4A), two mole-
cules are overlapped along the a-axis. Three kinds of hydrogen
bonds are observed along the c-axis [O1-H24 (2.442 Å),
O1-H25 (2.502 Å), and O2-H10 (2.522 Å)] (Figure 4B), and
the distances of all the hydrogen bonds are shorter than the sum
of the van der Waals radii21 of a hydrogen atom (1.20 Å) and
an oxygen atom (1.40 Å).
The crystal structure of the (R)-isomer of three-layered [3.3]-
PCP 3 has already been reported,3 and we report here the
molecular structure of the racemate of 3 (Figure 5, -160 °C).
In the unit cell, a pair of (R)- and (S)-isomers is present and
only the (R)-isomer is shown in the ORTEP drawing, where
both [3.3]PCP units assume the boat conformation different from
the parent 2 (chair). The boat/boat conformation of 3 was
predicted to be the most stable among the possible seven stable
isomers concerned with the trimethylene bridge based on DFT
calculations using the B3LYP functional and 6-31G* basis set.3
The three benzene rings are completely stacked, and the tran-
sannular distances of two [3.3]PCP units are 3.27 and 3.28 Å,
which are shorter than the corresponding two-layered [3.3]-
PCP 2 (3.31 Å). In the crystal-packing diagram of 3 (Figure
6), the CH/π interactions of the benzene rings with the
trimethylene protons between (R)- and (S)-isomers are observed,
and their average value is 2.86 Å, which is approximately the
sum of the van der Waals radii.21 Thus each isomer is arranged
regularly and stacked alternately.
Figure 7 shows the molecular structure of four-layered [3.3]-
PCP-dione 10 (meso, -160 °C). The ORTEP drawing shows
that the two [3.3]PCP units assume boat conformations different
from that of the parent 2, whereas the [3.3]PCP-dione unit has
a chair conformation comparable to that of the parent 1 (Figure
7A). The benzene rings of the central [3.3]PCP-dione unit are
parallel, while the outer benzene rings deviate from complete
stacking with a tilting of 6.1° (Figure 7B). The transannular
distances are 3.28 Å for the [3.3]PCP unit and 3.25 Å for the
dione unit, and these values are shorter than the corresponding
distances of 8 and the parents 1 and 2. In the crystal-packing
diagram of 10 (Figure 8), a molecule interacts with four
neighboring molecules by intermolecular hydrogen bonds (2.494
Å) between the carbonyl oxygen atom (O1) and the benzylic
proton (H12).
Figure 9 shows the molecular structure of four-layered [3.3]-
PCP 4 (meso, -150 °C), where the trimethylene bridges are
highly flexible and disordered even at -150 °C. The four ben-
zene rings are almost overlapped, but the two outer benzene
(19) X-ray structural analysis of 1 is shown in the Supporting Information.
(20) Gantzel, P. K.; Trueblood, K. N. Acta Crystallogr. 1965, 18, 958–968.
(21) PaulingL. The Nature of the Chemical Bonds ; Cornell University Press:
Ithaca, New York, 1960; p 260.
4436 J. Org. Chem. Vol. 73, No. 12, 2008

Three- and Four-Layered [3.3]Paracyclophanes
FIGURE 5. ORTEP drawing of the molecular structures of three-
layered [3.3]PCP 3 represented by the (R)-isomer (-160 °C): top (A)
and side (B) views.
FIGURE 7. ORTEP drawing of the molecular structures of four-layered
[3.3]PCP-dione 10 (-160 °C): top (A) and side (B) views.
[2.2] analogues, indicating less deformation of the benzene rings
of the [3.3]PCP.
Electronic Spectra. Figure 12 denotes the electronic absorp-
tion spectra of the multilayered [3.3]PCPs 2-5 in THF. Bath-
ochromic shift and hyperchromic effect are observed as the
layers are increased, but the magnitude is more significant for
two to three than for three to four. The absorption curves become
similar in shape and almost a straight line as the number of
layers increases. Racemic 5 shows a slightly more significant
bathochromic shift and hyperchromic effect compared to those
of meso 4, and this may be attributable to more effective
electronic interaction in the helical arrangement of the trimeth-
ylene bridges of 5. In the electronic spectra of multilayered
[3.3]PCP-diones, a similar but more significant bathochromic
shift and hyperchromic effect are observed as the number of
layers increases (Figure 13), and characteristic n-π* bands are
observed in the region of 280-300 nm.25 The electronic spectra
did not show any concentration dependence in the range of 1.0
× 10-4-10 × 10-4 M for 4 and 8.4 × 10-5-42 × 10-5 M for
10 in THF, respectively (Figure S33, Supporting Information).
FIGURE 6. Molecular stacking form of three-layered [3.3]PCP 3
(racemate) view along the a-axis.
rings are tilted by 2.5° toward the inner benzene ring. The tran-
sannular distances are 3.31 Å for the outer [3.3]PCP units and
3.29 Å for the inner one. In the crystal-packing diagram of 4
(Figure 10), a molecule interacts with four stacked molecules
via CH/π interactions between the benzene carbons and benzylic
protons. With regard to the distortion of the benzene rings
(Figure 11), the outer benzene rings are deformed into a boat
form while the inner benzene rings assume a twist form in
multilayered [3.3]PCPs. The torsion angles of the mean value
are listed in Table 1 along with those of multilayered [2.2]PCPs
as references. The torsion angles of multilayered [3.3]PCPs
(5.2-7.0° for a, 3.5-5.4° for b, and 6.4-8.1° for c) are
approximately half compared with those of the corresponding
(22) (a) Brown, C. J. J. Chem. Soc. 1953, 3265–3270. (b) Hope, H.; Bernstein,
J.; Trueblood, K. N. Acta Crystallogr., Sect. B 1972, 28, 1733–1743.
(23) Otsubo, T.; Horita, H.; Koizumi, Y.; Misumi, S. Bull. Chem. Soc. Jpn.
1980, 53, 1677–1682.
(24) Mizuno, H.; Nishiguchi, K.; Otsubo, T.; Misumi, S.; Morimoto, N.
Tetrahedron Lett. 1972, 13, 4981–4984.
(25) (a) Cram, D. J.; Helgeson, R. C. J. Am. Chem. Soc. 1966, 88, 3515–
3521. (b) Cookson, R. C.; Wariyar, N. S. J. Chem. Soc. 1956, 2302–2311.
J. Org. Chem. Vol. 73, No. 12, 2008 4437

Shibahara et al.
FIGURE 9. ORTEP drawing of the molecular structures of four-layered
[3.3]PCP 4 (-150 °C): top (A) and side (B) views. Hydrogen atoms
are omitted for clarity.
FIGURE 8. The short contacts of four-layered [3.3]PCP-dione 10
viewed along the c-axis. (A) The crystal-packing diagram. (B) Hydrogen
bonds between the carbonyl oxygen (O1) and the benzylic proton (H12).
Charge Transfer Interaction. The π-electron donating ability
of the cyclophanes can be qualitatively estimated by measurement
of the λmax of the CT band between a cyclophane and TCNE. In
the two-layered [3.3]CPs, [3.3]PCP 2 (λmax 606 nm) shows a
significantly stronger CT interaction than [3.3]MCP (λmax 509 nm)
and [3.3]MPCP (λmax 510 nm). The multilayered [3.3]MCPs [λmax
550 (three layers)-588 (six layers) nm in CHCl3] showed moderate
electron-donating ability2 compared to multibridged [3n]CPs [λmax
594 {[33](1,3,5)CP}-728 {[36](1,2,3,4,5,6)CP} nm in CHCl3].15b
The CT absorption spectra of the multilayered [3.3]PCPs 2-5 and
multilayered [3.3]PCP-diones 1, 8, 10, and 11 are shown in Figure
14 and Supporting Information Figure S26, respectively, and the
λ
max values of the CT bands are summarized in Table 2. The 1:1
stoichiometry of the CT complex was confirmed (Figures S27 and
S28, Supporting Information). The λmax shows a significant red
shift with an increasing number of layers [2: λmax 606 nm; 3: 670
nm; 4 (meso): 716 nm; and 5 (racemic): 723 nm in CHCl3], but
the changes in the λmax from two to three (64 nm) and three to
four (46 and 53 nm) become smaller. The magnitude of the
FIGURE 10. CH/π Interaction of four-layered [3.3]PCP 4.
electron-donating ability of multilayered [3.3]PCPs is more sig-
nificant than that of multilayered [3.3]MCPs. In the UV/vis spectra,
4438 J. Org. Chem. Vol. 73, No. 12, 2008

Three- and Four-Layered [3.3]Paracyclophanes
FIGURE 11. Distortion of benzene rings in multilayered [m.m]PCPs.
TABLE 1. Torsion Angles of Multilayered [m.m]PCPs.
multilayered [3.3]PCPs
two-layered [2.2]PCP22
a (deg)
13
b (deg)
c (deg)
11
monobromo three-layered [2.2]PCP23 12.2
11.2
11.2
3.6
4.2
5.4
13.6
13.4
tetramethyl four-layered [2.2]PCP24
two-layered [3.3]PCP 220
three-layered [3.3]PCP 3
12.7
6.4
5.2
6.3
6.1
8.1
6.8
four-layered [3.3]PCP 4
two-layered [3.3]PCP-dione 119
three-layered [3.3]PCP-dione 8
four-layered [3.3]PCP-dione 10
4.0
6.8,a 5.6b 3.7,a 5.4b
7.5
6.4
7.0
3.5
a Tortion angles of the [3.3]PCP unit. b Tortion angles of [3.3]PCP-dione
unit.
FIGURE 13. Electronic spectra of multilayered [3.3]PCP-diones 1, 8,
10, and 11 in THF.
FIGURE 12. Electronic spectra of multilayered [3.3]PCPs 2-5 in THF.
FIGURE 14. Charge-transfer absorption bands of multilayered [3.3]PCPs
2-5 in CHCl3.
we noted that 5 (racemic) shows a slightly more significant bath-
ochromic shift and hyperchromic effect than 4 (meso), suggesting
more effective electronic interaction in 5 than in 4. The slight red
shift of the CT absorption band (λmax 723 nm) of 5 compared to
that of 4 (λmax 716 nm) also suggests that the helical arrangement
of the trimethylene bridges is more effective in the CT interaction.
In the multilayered [3.3]PCP-diones, the λmax appears at
594-629 nm for three- to four-layered [3.3]PCP-diones 8, 10,
and 11, and these values are comparable to those of two-layered
[3.3]PCP 2 (606 nm). This result suggests that the -CH2COCH2-
bridge serves as an insulator irrespective of transannular
distances similar to those of the [3.3]PCP unit and [3.3]PCP-
dione unit. This indicates that the -CH2COCH2- bridge
interferes with the electronic interaction between the completely
overlapped benzene rings. A similar result that the [3.3]MCP-
dione moiety having an antigeometry in multilayered [3.3]MCPs
interferes with transannular π-electronic interaction suggests the
J. Org. Chem. Vol. 73, No. 12, 2008 4439

Shibahara et al.
TABLE 2. CT Bands of Multilayered [3.3]PCPs-TCNE in CHCl3.
dithia[3.3]PCP 14, the HOMO level is greatly lowered (-5.90
eV). 2,11-Diaza[3.3]PCP 15 shows an HOMO level (-5.52 eV)
comparable to that of the parent 2, but we could not measure
the λmax because of the insolubility of the complex with TCNE,
whereas the HOMO level is significantly lowered by the
introduction of acetyl (16: -6.04 eV) and trifluoroacetyl groups
(17: -6.36 eV) to the nitrogen atoms of 15. Thus we confirmed
that the electron-donating ability of [3.3]PCPs is strongly
dependent on the central atom of the -CH2XCH2- bridge and
the substituents on the central atom.
multilayered [3.3]PCPs
TCNE complex λmax (nm)
two-layered [3.3]PCP 2a
606, 489
670, 425
three-layered [3.3]PCP 3b
four-layered [3.3]PCP 4
716, 445
four-layered [3.3]PCP 5
723, 471, 383c
two-layered [3.3]PCP-dione 1
three-layered [3.3]PCP-dione 8
four-layered [3.3]PCP-dione 10
four-layered [3.3]PCP-dione 11
594, 392
613, 427
629, 435
a The longest wavelength in CH2Cl2 was 599 nm, in ref 11a. b 655
and 421 nm in CH2Cl2, in ref 12b. c Shoulder
Electrochemical Properties. To find a correlation between
the λmax of the CT bands with TCNE and the oxidation poten-
tials of multilayered [3.3]PCPs, the CV in Cl2CHCHCl2 was
measured (Figure 16 and Supporting Information Figure S32).
The oxidation potentials and the λmax of the CT bands of
multilayered [3.3]PCPs are summarized in Table 4 along with
the data for multibridged [3n]CPs as references.15b,29 Three- and
four-layered [3.3]PCPs 3 (racemic), 4 (meso), and 5 (racemic)
show reversible redox processes, whereas two-layered [3.3]PCP
2 and diones 1, 8, 10, and 11 show irreversible CV profiles.
The first half-wave oxidation potentials [E1/2(I)] are +0.61 V
for 3, +0.40 V for 4, and +0.44 V for 5 (vs Fc/Fc+), respec-
tively, and the data are comparable to the λmax values of the
TCNE complexes of 3, 4, and 5. The E1/2(I) of four-layered
[3.3]PCPs 4 and 5 are almost comparable to, but slightly less
than, that of [36]CP (E1/2 +0.39 V vs Fc/Fc+, Cl2CHCHCl2).29
Table 4 shows very good correlation of the oxidation potentials
of the cyclophanes and the λmax of the CT bands of the
cyclophane-TCNE complexes, and this indicates that the
magnitude of the CT interactions is mostly determined by the
electron-donating ability (oxidation potential) of a cyclophane,
and similar donor-accepter interactions are operative in mul-
tilayered and multibridged cyclophanes. Thus, direct comparison
of the π-electron-donating ability of multilayered and multibridged
[3.3]cyclophanes is now becoming feasible.
FIGURE 15. Two-Layered [3.3]PCPs 12-17.
importance of the through-bond interaction.2 These results
suggest that the electronic interaction in multilayered [3.3]MCPs
and [3.3]PCPs should be significantly affected by “through-
bond” interaction rather than “through-space” interaction. An
analysis of this problem by means of the Natural Bond Orbital
(NBO) method26 will be reported elsewhere.
To test the dependence of the electron-donating ability (λmax
of the CT band) on the kind of central atoms of the -CH2XCH2-
bridge in [3.3]PCPs, the λmax of the CT band with TCNE was
measured and the HOMO energy was estimated by the DFT
(B3LYP/6-31G* level27) calculations (Gaussian 0328). The
magnitude of the CT interaction is strongly affected by the
central atoms of the -CH2XCH2- bridges (X ) C, N, S) and
the substituents on the atoms (Figure 15 and Supporting
Information Figure S29). The -CH2CH2CH2- bridge (2) is the
most effective for CT interaction in the [3.3]PCPs, but the
introduction of an acetoxy group to the central sp3 carbon of
the -CH2CH2CH2- bridge (12) slightly lowers the electron-
donating ability of 2, and introduction of acetal groups (13)
further lowers the donating ability, while [3.3]PCP-dione 1 does
not show any CT band. The nitrogen-containing [3.3]PCPs
(15-17) do not show clear CT bands. In principle, this tendency
corresponds with the HOMO energy level of the [3.3]PCPs
(Table 3 and Supporting Information Figures S30 and S31), but
the acetal 13 (-5.36 eV) shows much lower electron-donating
ability irrespective of the higher HOMO level of 2. In 2,11-
3. Conclusions
We have successfully synthesized up to four-layered [3.3]PCPs
using the EbsMIC method, and a similar repetition of a series
of reactions may lead to the formation of higher five- and six-
layered [3.3]PCPs. For the synthesis of the optically active five-
and six-layered [3.3]PCPs, synthesis of the coupling precursors,
bis(bromomethyl)-(R)-two-layered, and bis(bromomethyl)-(R,R)-
three-layered [3.3]PCPs is required, and the synthesis of these
chiral bis(bromomethyl)[3.3]PCPs is in progress. In the 1H NMR
spectra, all the aromatic protons showed an upfield shift caused
by the stacked benzene rings that could affect not only the
neighboring rings but also more remote ones, but the magnitude
of the upfield shift was smaller than that of the [2.2]homologues.
In addition, the four-layered [3.3]PCPs 4 (meso) and 5 (recemic)
exhibited isomeric properties inherent to their helical structures.
The X-ray structural analysis revealed that the [3.3]PCP unit
assumes a chair conformation comparable to that of the parent
[3.3]PCP 2, while the three-layered [3.3]PCP 3 assumes a boat/
boat conformation. In the four-layered [3.3]PCP-dione 10, both
the outer [3.3]PCP units have a boat conformation, whereas the
inner unit has a chair conformation. From these results, [3.3]PCP
and the dione units are flexible and can change their conforma-
tion so as to adopt a crystal packing force. In the four-layered
(26) Carpenter, J. E.; Weinhold, F. J. Mol. Struct. 1988, 169, 41–62.
(27) (a) Becke, A. D. J. Chem. Phys. 1993, 98, 5648–5652. (b) Lee, C.;
Yang, W.; Parr, R. G. Phys. ReV. B 1988, 37, 785–789.
(28) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb,
M. A.; Cheeseman, J. R.; Montgomery, J. A., Jr.; Vreven, T.; Kudin, K. N.;
Burant, J. C.; Millam, J. M.; Iyengar, S. S.; Tomasi, J.; Barone, V.; Mennucci,
B.; Cossi, M.; Scalmani, G.; Rega, N.; Petersson, G. A.; Nakatsuji, H.; Hada,
M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa, J.; Ishida, M.; Nakajima, T.;
Honda, Y.; Kitao, O.; Nakai, H.; Klene, M.; Li, X.; Knox, J. E.; Hratchian,
H. P.; Cross, J. B.; Bakken, V.; Adamo, C.; Jaramillo, J.; Gomperts, R.;
Stratmann, R. E.; Yazyev, O.; Austin, A. J.; Cammi, R.; Pomelli, C.; Ochterski,
J. W.; Ayala, P. Y.; Morokuma, K.; Voth, G. A.; Salvador, P.; Dannenberg,
J. J.; Zakrzewski, V. G.; Dapprich, S.; Daniels, A. D.; Strain, M. C.; Farkas, O.;
Malick, D. K.; Rabuck, A. D.; Raghavachari, K.; Foresman, J. B.; Ortiz, J. V.;
Cui, Q.; Baboul, A. G.; Clifford, S.; Cioslowski, J.; Stefanov, B. B.; Liu, G.;
Liashenko, A.; Piskorz, P.; Komaromi, I.; Martin, R. L.; Fox, D. J.; Keith, T.;
Al-Laham, M. A.; Peng, C. Y.; Nanayakkara, A.; Challacombe, M.; Gill,
P. M. W.; Johnson, B.; Chen, W.; Wong, M. W.; Gonzalez, C.; Pople, J. A.
Gaussian 03, Revision C.02; Gaussian, Inc.: Wallingford, CT, 2004.
(29) Yasutake, M.; Koga, T.; Sakamoto, Y.; Komatsu, S.; Zhou, M.; Sako,
K.; Tatemitsu, H.; Onaka, S.; Aso, Y.; Inoue, S.; Shinmyozu, T. J. Am. Chem.
Soc. 2002, 124, 10136–10145.
4440 J. Org. Chem. Vol. 73, No. 12, 2008

Three- and Four-Layered [3.3]Paracyclophanes
TABLE 3. Predicted Energy of the HOMO (eV) in Multilayered [3.3]PCPs (DFT, B3LYP/6-31G* level)
1
2
12
13
14
15
16
17
3
4
5
8
10
11
-5.83
-5.48
-5.71
-5.36
-5.90
-5.52
-6.04
-6.36
-5.14
-4.96
-4.99
-5.44
-5.28
-5.30
[3.3]PCP 4, the trimethylene bridges are highly flexible and
disordered at -150 °C. The benzene rings of the [3.3]PCPs are
far less distorted compared to those of the [2.2]system. In the
electronic spectra, bathochromic and hyperchromic shifts were
observed, but the magnitude was smaller and showed struc-
tureless absorption curves as the number of layers increased.
In the CT interaction of multilayered [3.3]PCPs, the λmax shifted
to a longer wavelength with the increase in the number of layers.
In contrast, all multilayered [3.3]PCP-diones 8, 10, and 11
showed interactions similar to those of two-layered[3.3]PCP 2.
These results suggested the importance of the through-bond
π-electronic interaction, and we confirmed that the electron-
donating ability of [3.3]PCPs is strongly dependent on the central
atom of the -CH2XCH2- bridge and the substituent on the central
atoms. In the electrochemical properties, three- and four-layered
[3.3]PCPs 3 (racemic), 4 (meso), and 5 (racemic) showed reversible
redox processes, and 4 and 5 showed comparable electron-donating
ability [E1/2(I); +0.40 (4) and +0.44 (5) V (vs Fc/Fc+)] to that of
[36]CP. Very good correlation between the λmax of the CT bands
with TCNE and the E1/2 values is observed, and the electron-
donating ability of the multilayered [3.3]PCPs can now be
compared to those of multibridged [3n]CPs.
We will continue the optical resolution and determination of
the absolute configuration of four-layered [3.3]PCP 5 (racemic)
by comparison of the observed CD spectra with the calculated
ones. Detailed analysis of through-space and through-bond inter-
action in the three- to four-layered [3.3]PCPs will also be repor-
ted by one of our collaborators.
4. Experimental Section
5,8-Bis(bromomethyl)[3.3]paracyclophane 6 and EbsMIC adduct
7 were synthesized by similar procedures as described in ref 3.
5,8-Bis[2-isocyano-2-(ethylbenzenesulfonyl)ethyl][3.3]paracy-
clophane, 9. A mixture of n-Bu4NI (810 mg) and NaOH (18 g)
dissolved in 42 mL of water and CH2Cl2 (67 mL) was cooled in
an ice bath with stirring. To the mixture was added in one portion
of a CH2Cl2 (45 mL) solution of EbsMIC 7 (7.36 g, 35.2 mmol).
After 30 min, the bromide 6 (4.49 g, 10.6 mmol) dissolved in
CH2Cl2 (67 mL) was added in one portion. The mixture was stirred
for 1 h in the ice bath, then at room temperature for 3 h. The reaction
mixture was washed with water, dried with MgSO4, and concen-
trated to a volume of ca. 50 mL at room temperature. The con-
centrate was diluted with MeOH (100 mL) and stored in a freezer.
The precipitate was collected by filtration and washed with MeOH.
Purification of the crude product by silica gel column chromatog-
raphy with CH2Cl2 (Rf 0.57) afforded two-layered EbsMIC adduct
9 (5.75 g, 80%). 9: white powder (CH2Cl2/MeOH), mp 137 °C
(dec); IR (KBr) ν 2134 (NC), 1334 and 1153 (SO2) cm-1; 1H NMR
(300 MHz, CDCl3) δ 1.28 (t, J ) 7.6 Hz, 6H, CH2CH3), 1.9-2.2
(m, 4H, CH2CH2CH2), 2.5-2.7 (m, 6H, CH2CH2CH2 and CH2CH),
2.77 (q, J ) 7.6 Hz, 4H, CH2CH3), 2.8-2.9 (m, 4H, CH2CH2CH2),
3.81 (dd, J ) 13.9, 2.1 Hz, 2H, CH2CH), 4.30 (dd, J ) 11.5, 2.2
Hz, 2H, CH2CH), 6.59 (s, 2H, ArH), 6.68 (dd, J ) 7.8, 1.6 Hz,
2H, ArH), 6.77 (dd, J ) 7.8, 1.6 Hz, 2H, ArH), 7.46 (d, J ) 8.5
Hz, 4H, ArH), 7.93 (d, J ) 8.4 Hz, 4H, ArH); HRMS (FAB) m/z
calcd for C40H42N2O4S2 678.2586 [M+], found 678.2590. Anal.
Calcd for C40H42N2O4S2: C, 70.77; H, 6.24; N, 4.13. Found: C,
70.53; H, 6.18; N, 4.06.
FIGURE 16. Cyclic voltammograms of multilayered [3.3]PCPs 3, 4,
and 5 in Cl2CHCHCl2/0.1 M Bu4NPF6 observed at a potential scan
rate of 20 mV s-1
a
TABLE 4. Oxidation Potentials in Cl2CHCHCl2 and the λmax
Values of the CT Bands in CHCl3
TCNE
E1/2(I)
Epa(I)
Epa(I)
complex
CPs
(V vs Fc/Fc+) (V vs Ag/AgCl) (V vs Fc/Fc+) λmax (nm)
[3.3]PCP 2
three-layered
[3.3]PCP 3
four-layered
[3.3]PCP 4
four-layered
[3.3]PCP 5
two-layered
dione 1
three-layered
dione 8
four-layered
dione 10
four-layered
dione 11
[33](1,3,5)CP
[34](1,2,3,5)CP
[34](1,2,4,5)CP
[35]CP
+1.13 (sh)
+0.91
+0.88
+0.66
606
670
Four-Layered [3.3]Paracyclophane-Diones C2h Isomer 10
and D2 Isomer 11. To a refluxing mixture of n-Bu4NI (1.0 g) and
NaOH (21 g) dissolved in 50 mL of water and CH2Cl2 (700 mL)
was added dropwise a mixture of the EbsMIC adduct 9 (2.02 g,
2.37 mmol) and the bromide 6 (1.26 g, 2.37 mmol) dissolved in
CH2Cl2 (500 mL) over a period of 8 h, and the mixture was refluxed
for an additional 12 h. After cooling, the reaction mixture was
washed with water then concentrated to a volume of ca. 300 mL,
and the concentrate was treated with concentrated HCl (30 mL)
for 2 h at room temperature. The mixture was washed with brine,
dried with MgSO4, and concentrated to dryness to give the crude
mixture of isomeric ketones, meso 10 and racemic 11. The less
soluble 10 was separated from the readily soluble 11 by treatment
with acetonitrile.
+0.61
+0.40
+0.44
+0.69
+0.44
+0.48
+0.87
+0.89
+0.81
+0.86
716
723
+0.73
+1.13
+1.14 (sh)
+1.06
594
613
629
+1.12
+1.31
+1.04
+1.02
+0.87
+0.73
+1.01
+0.74
+0.72
+0.57
+0.43
594
632
Purification of the crude 10 by silica gel column chromatography
with benzene (Rf 0.17) afforded the C2h isomer 10 (239 mg, 12%).
10: colorless plates (benzene), mp 247 °C dec; IR (KBr) ν 1686
+0.69
+0.66
+0.51
+0.39
684
728
1
[36]CP
(CdO) cm-1; H NMR (300 MHz, CDCl3) δ 1.7-1.9 (m, 8H,
CH2CH2CH2), 2.2-2.4 (m, 4H, CH2CH2CH2), 2.49 (t, J ) 5.3 Hz,
8H, CH2CH2CH2), 2.65-2.85 (m, 4H, CH2CH2CH2), 3.26 (d, J )
a Containing 0.1 M Bu4NPF6, scan rate 20 mV/s. sh: shoulder.
J. Org. Chem. Vol. 73, No. 12, 2008 4441

Shibahara et al.
13.0 Hz, 4H, CH2COCH2), 3.69 (d, J ) 13.0 Hz, 4H, CH2COCH2),
5.87 (s, 4H, ArH), 6.39 (dd, J ) 7.7, 1.5 Hz, 4H, ArH), 6.47 (dd,
J ) 7.7, 1.5 Hz, 4H, ArH); 13C NMR (75 MHz) δ 28.3, 32.6, 35.4,
49.3, 127.2, 129.6, 131.4, 133.6, 136.3, 138.0, 207.7; HRMS (FAB)
m/z calcd for C42H44O2 580.3341 [M+], found 580.3337. Anal.
Calcd for C42H44O2: C, 86.85; H, 7.64. Found: C, 86.49; H, 7.63.
X-ray Crystallographic Study. Measurements were made by
using graphite-monochromated Mo KR (λ ) 0.71069 Å; 3, 4, 8,
and 10) or Cu KR (λ ) 1.54187 Å; 1) radiation and a rotating
anode generator. The crystal structures were solved by direct
methods [SIR92]30 (3), [SIR97]31 (1, 8, and 10), and [SHELX97]32
(4), and refined by the full-matrix least-squares methods. The non-
hydrogen atoms were refined anisotropically and hydrogen atoms
were refined isotropically. The computations were performed wth
the teXan package33 (3, 8, and 10) or the Crystalstructure34 (1 and
4). Crystallographic data for the structural analyses of 1, 3, 4, 8,
and 10 have been deposited within the Cambridge Crystallographic
Data Centre (CCDC) as 666229, 665070, 665072, 665071, and
665073, respectively. Copies of this information may be obtained
from The Director, CCDC, 12 Union Road, Cambridge, CB2 1EZ,
U.K. (fax +44 1223 336 033; e-mail deposit@ccdc.cam.ac.uk; or
http://www.ccdc.cam.ac.uk/deposit).
Purification of the crude 11 by silica gel column chromatography
with benzene (Rf 0.17) afforded the pure D2 isomer 11 (105 mg,
7%). 11: colorless needles (EtOH), mp 248 °C dec; IR (KBr) ν
1
1695 (CdO) cm-1; H NMR (300 MHz, CDCl3) δ 1.7-1.9 (m,
8H, CH2CH2CH2), 2.15-2.3 (m, 4H, CH2CH2CH2), 2.4-2.6 (m,
8H, CH2CH2CH2), 2.65-2.80 (m, 4H, CH2CH2CH2), 3.21 (d, J )
12.8 Hz, 4H, CH2COCH2), 3.60 (d, J ) 12.8 Hz, 4H, CH2COCH2),
5.94 (s, 4H, ArH), 6.39 (dd, J ) 7.6, 1.5 Hz, 4H, ArH), 6.48 (dd,
J ) 7.6, 1.5 Hz, 4H, ArH); 13C NMR (75 MHz) δ 28.1, 32.5, 35.5,
49.1, 127.2, 129.7, 131.9, 136.4, 138.1, 207.7; HRMS (FAB) m/z
calcd for C42H44O2 580.3341 [M+], found 580.3341. Anal. Calcd
for C42H44O2: C, 86.85; H, 7.64. Found: C, 86.58; H, 7.68.
Acknowledgement. We are indebted to Professor Takahiko
Inazu for his helpful suggestions. We gratefully acknowledge
the financial support by a Theme Project of Molecular Archi-
tecture of Organic Compounds for Functional Design (Professor
Tahsin J. Chow), Institute of Chemistry, Academia Sinica,
Taiwan, ROC. We are also grateful for the financial support
from a Grant-in-Aid for Scientific Research (B) (No. 18350025)
from the Ministry of Education, Culture, Sports, Science and
Technology, Japan.
Four-Layered [3.3]Paracyclophanes C2h Isomer 4 and D2
Isomer 5. A mixture of C2h isomer 10 (153 mg, 0.264 mol), 98%
NH2NH2 ·H2O (3 mL), NH2NH2 ·2HCl (600 mg), KOH (2.6 g),
and diethylene glycol (55 mL) was heated at 130 °C for 6 h and
then at 200 °C for 5 h with stirring. After cooling, the mixture was
poured into ice-water, acidified with concentrated HCl, and
extracted with CH2Cl2. The CH2Cl2 solution was washed with brine,
dried with MgSO4, and concentrated to dryness. Purification of the
residue by silica gel column chromatography with benzene/hexane
(5:4, Rf 0.86) gave 4 (105 mg, 72%) as white crystals. 4: colorless
1
plates (benzene), mp 295 °C dec; H NMR (300 MHz, CDCl3) δ
Supporting Information Available: Synthetic procedure for
12 and 13; summary of crystallographic data and refinement
1.6-1.95 (m, 12H, CH2CH2CH2), 2.15-2.80 (m, 24H, CH2CH2CH2),
5.72 (s, 4H, ArH), 6.35 (dd, J ) 7.6, 1.5 Hz, 4H, ArH), 6.48 (dd,
J ) 7.6, 1.5 Hz, 4H, ArH); 13C NMR (75 MHz) δ 27.9, 28.9, 32.8,
35.9, 127.0, 129.3, 132.7, 134.6, 134.9, 138.1; HRMS (FAB) m/z
calcd for C42H48 552.3756 [M+], found 552.3754. Anal. Calcd for
C42H48: C, 91.25; H, 8.75. Found: C, 90.92; H, 8.71.
1
details for 1, 3, 4, 8, and 10; H and 13C NMR spectra of all
new compounds; charge-transfer absorption bands of multilay-
ered [3.3]PCP-diones, three-layered [3.3]PCP 3 and four-layered
[3.3]PCP 4, and two-layered [3.3]PCPs in CHCl3; computational
results; cyclic voltammograms of 1, 2, 8, 10, and 11; and
electronic spectra of 4 and 10 in THF. This material is available
free of charge via the Internet at http://pubs.acs.org.
A mixture of D2 isomer 11 (72 mg, 0.125 mol), 98% NH2NH2 ·
H2O (4 mL), NH2NH2 ·2HCl (320 mg), KOH (1.3 g), and diethylene
glycol (50 mL) was heated at 130 °C for 18 h and then at 200 °C
for 6 h with stirring. After cooling, the mixture was poured into
ice-water, acidified with concentrated HCl, and extracted with
CH2Cl2. The CH2Cl2 solution was washed with brine, dried with
MgSO4, and concentrated to dryness. Purification of the residue
by silica gel column chromatography with benzene/hexane (5:4,
Rf 0.86) gave 5 (16 mg, 23%) as white crystals. 5: Colorless plates
(benzene), mp 257 °C dec; 1H NMR (300 MHz, CDCl3) δ 1.6-1.9
(m, 12H, CH2CH2CH2), 2.05-2.75 (m, 24H, CH2CH2CH2), 5.77
(s, 4H, ArH), 6.36 (dd, J ) 7.8, 1.8 Hz, 4H, ArH), 6.49 (dd, J )
7.8, 1.7 Hz, 4H, ArH); 13C NMR (75 MHz) δ 27.5, 28.6, 32.7,
35.8, 126.9, 129.3, 130.9, 134.6, 134.7, 138.0; HRMS (FAB) m/z
calcd for C42H48 552.3756 [M+], found 552.3735. Anal. Calcd for
C42H48: C, 91.25; H, 8.75. Found: C, 91.06; H, 8.75.
JO8003309
(30) Altomare, A.; Burla, M. C.; Camalli, M.; Cascarano, M.; Giacovazzo,
C.; Guagliardi, A.; Polidori, G. J. Appl. Crystallogr. 1994, 27, 435.
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C.; Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.; Spagna, R. J. Appl.
Crystallogr. 1999, 32, 115–119.
(32) Sheldrick, G. M. SHELX-97, Program for the Refinement of Crystal
Structures; University of Goettingen: Goettingen, Germany, 1997.
(33) Crystal Structure Analysis Package; Molecular Structure Corporation,
1985 and 1999.
(34) CrystalStructure 3.8, Crystal Structure Analysis Package; Rigaku and
Rigaku/MSC, 2000-2006.
4442 J. Org. Chem. Vol. 73, No. 12, 2008