Alternative general synthetic routes to [2.2]cyclophanes and [3.2]cyclophanes from [3.3]cyclophane-2,11-diones by photodecarbonylation, and a structural study of [3.2]metacyclophanes

Article abstract of DOI:10.1002/1099-0690(200107)2001:13<2487::AID-EJOC2487>3.0.CO;2-F

Photodecarbonylation of [3.3]cyclophane-2,11-diones, which are readily prepared by TosMIC coupling, affords [2.2]cyclophanes in high yield. This method also provides a general synthetic method for [3.2]cyclophan-2-ones by taking advantage of the fact that this photochemical reaction proceeds in a stepwise manner through [3.2]cyclophan-2-ones. A series of [2.2]cyclophanes, [3.2]cyclophanes, and [3.3]cyclophanes can thus be made available from the common precursor [3.3]cyclophane-2,11-diones. In sharp contrast to the preferred syn geometry of [3.3]metacyclophanes, [3.2] metacyclophanes adopt anti geometries and the aryl ring inversion process is observed by variable-temperature ¹H NMR spectroscopy. In the crystalline state, the two aryl rings of anti-[3.2]metacyclophanes are almost parallel in spite of the unsymmetrical bridge length; they overlap only at the C-9 and C-17 positions, and the transannular distances are shorter than the corresponding distances in [3.3]metacyclophane-2,11-dione.

Full text of DOI:10.1002/1099-0690(200107)2001:13<2487::AID-EJOC2487>3.0.CO;2-F

FULL PAPER
Alternative General Synthetic Routes to [2.2]Cyclophanes and [3.2]Cyclophanes
from [3.3]Cyclophane-2,11-diones by Photodecarbonylation, and a Structural
Study of [3.2]Metacyclophanes[‡]
Hajime Isaji,[a] Mikio Yasutake,[a] Hiroyuki Takemura,[c] Katsuya Sako,[d]
Hitoshi Tatemitsu,[d] Takahiko Inazu,[b] and Teruo Shinmyozu*[a]
Keywords: Conformational analysis / Cyclophanes / NMR spectroscopy / Photochemistry / Synthetic methods
Photodecarbonylation of [3.3]cyclophane-2,11-diones, which
preferred syn geometry of [3.3]metacyclophanes, [3.2]meta-
are readily prepared by TosMIC coupling, affords [2.2]cyclo- cyclophanes adopt anti geometries and the aryl ring inver-
phanes in high yield. This method also provides a general sion process is observed by variable-temperature 1H NMR
synthetic method for [3.2]cyclophan-2-ones by taking ad-
vantage of the fact that this photochemical reaction proceeds
in a stepwise manner through [3.2]cyclophan-2-ones. A
series of [2.2]cyclophanes, [3.2]cyclophanes, and [3.3]cyclo-
spectroscopy. In the crystalline state, the two aryl rings of
anti-[3.2]metacyclophanes are almost parallel in spite of the
unsymmetrical bridge length; they overlap only at the C-9
and C-17 positions, and the transannular distances are
phanes can thus be made available from the common pre- shorter than the corresponding distances in [3.3]metacyclo-
cursor [3.3]cyclophane-2,11-diones. In sharp contrast to the
phane-2,11-dione.
Introduction
reporting of an alternative synthetic method for [2.2]CPs by
decarbonylation of 1, we have found that this method also
provides a general synthetic method for [3.2]CP-2-ones 3,
by taking advantage of the fact that this reaction proceeds
in a stepwise manner through [3.2]CP-2-ones 3. This
method thus provides new routes to the synthesis of
[2.2]CPs and [3.2]CPs 2 and 3 through adjustment of the
irradiation time while using the same starting material, 1,[8]
as used for the synthesis of [3.3]CPs 4 (Scheme 1).
[3.3]Cyclophanes (CPs) undergo two types of photo-
chemical reactions: excitation of the π-π* band of multi-
bridged [3n]CPs (n ϭ 3,[3] 4[4]) results in the formation of
polycyclic cage compounds by [2ϩ2] cycloaddition of the
facing benzene rings, followed by rearrangement of the car-
bocation species generated by protonation of a cyclobutane
ring of the cycloadduct, while excitation of the n-π* band
of [3.3]CP-2,11-diones 1 induces decarbonylation to give
[2.2]CPs 2 in high yields, as has been reported in brief.[5]
Quinkert et al. first reported the light-induced decar-
bonylation of ketones in benzene in 1963[6a] and found that
1,3-diphenyl-2-propanones afford 1,2-diphenylethanes in
high yields.[6aϪ6d] In the course of our studies of multilay-
ered [3.3]metacyclophanes (MCPs), we noticed that the
characteristic n-π* bands of the structural units, [3.3]MCP-
2,11-diones, appear in the 280Ϫ330 nm region.[7] Since our
[‡]
Conformational Analysis of [3.3]Cyclophanes, 6. Ϫ Part 5:
Scheme 1. A new synthetic route to [2.2]cyclophanes and [3.2]cyclo-
phanes 2 and 3 by photodecarbonylation of [3.3]cyclophane-2,11-
dione 1
Ref.[2] This paper is taken in part from the Ph.D. Dissertation
of H. Isaji of Kyushu University.[1]
[a]
Institute for Fundamental Research of Organic Chemistry
(IFOC), Kyushu University,
Fukuoka 812-8581, Japan
General synthetic methods for [2.2]CPs have been already
established.[9] Most of them employ ring-contraction reac-
tions of 2,11-diheteroatom-substituted [3.3]CPs. Photo-
chemical elimination of sulfur[10] or selenium atoms[11] from
[3.3]CP 2,11-disulfide or diselenide and flash vacuum pyro-
lysis of sulfones[10b,12,13] obtained by the oxidation of the
corresponding sulfides are the most general methods. We
have reported that 2,11-diaza[3.3]CPs may be converted
into the corresponding [2.2]CPs through their nitroso deriv-
Fax: (internat.) ϩ 81-92/642-2735
E-mail: shinmyo@ms.ifoc.kyushu-u.ac.jp
[b]
Department of Chemistry, Graduate School of Science,
Kyushu University,
Fukuoka, 812-8581, Japan
[c]
Department of Chemistry, Faculty of Science, Kyushu
University,
Fukuoka 810-8560, Japan
[d]
Department of Systems Management and Engineering, Nagoya
Institute of Technology,
Nagoya 466-8555, Japan
Eur. J. Org. Chem. 2001, 2487Ϫ2499
WILEY-VCH Verlag GmbH, 69451 Weinheim, 2001
1434Ϫ193X/01/0713Ϫ2487 $ 17.50ϩ.50/0
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T. Shinmyozu et al.
FULL PAPER
atives by reductive elimination of nitrogen.[14] Photoextru-
sion reactions of CO2 from cyclic diesters can also be ap-
plied to the synthesis of [2.2]paracyclophanes (PCPs)[15]
and [2.2]heterophanes.[16]
Table 1. Yields of [2.2]cyclophanes and [3.2]cyclophane-2-ones pre-
pared by irridiation of diones with a 400-W high-pressure Hg lamp
Recently, Vögtle et al. reported selective ketone pyrolysis
as a new synthetic method for production of monocyclic
and polycyclic hydrocarbons. Flash vacuum pyrolysis (10Ϫ5
Torr, 610Ϫ650 °C) of [3.3]CP-2,11-diones 1, for example,
afforded [2.2]CPs 2 in moderate yields.[17] This ketone pyro-
lysis is widely applicable to the synthesis of triple-bridged
cyclophanes and the large cavity cyclophanes starting from
[3n]CP-(one)n.
Yamato et al. have reported an orthodox synthesis of
9,17-dimethyl[3.2]MCPs,[18a] while Tsuge et al. have studied
the transannular π-electronic interaction of 9,17-dimethyl-
[3.2]MCPs, and concluded that the electronic nature is
transmitted less effectively to the benzene ring of the other
side in the [3.2]MCP than in [2.2]homologue.[18b][18c] Vögtle
et al. reported the synthesis of helical and planar-chiral ox-
1
a[2.2]pyridinophanes, and studied the dynamic H NMR
spectra of their synthetic intermediates, thia[3.2]pyridino-
phanes.[19]
The weaker π-electron-donating ability of [3.2]PCP[20] rel-
ative to that of [2.2]PCPs and [3.3]PCPs seems to be the
most likely reason why the [3.2]CPs have not attracted much
attention, while the lack of general and facile synthetic
methods has hindered further studies of them. We describe
here an alternative decarbonylation reaction by photochem-
ical processes; this method provides an alternative synthetic
route to [2.2]CPs and the simplest approach to the synthesis
of [3.2]CPs, which are in general inaccessible directly.
Results and Discussion
Synthesis
Photochemical treatment of [3.3]CP-2,11-dione 1 in ben-
zene gave the corresponding [2.2]CP 2 in satisfactory yields.
The isolated yields of products and irradiation times are
summarized in Table 1. A benzene solution (4.0 ϫ 10Ϫ3
mol/L) of [3.3]MCP-2,11-dione 5 was irradiated with a
high-pressure Hg lamp (400 W) as the internal light source
at ambient temperatures, while nitrogen was bubbled
through the solution. The reaction was rather slow, but
[2.2]MCP 6 was obtained in 95% yield after 20 h of irradi-
ation. When irradiation was stopped after 4 h, 9% of 6 and tyl-4,12-dimethyl[2.2]MCP 18,[21] and the synthesis of
57% of [3.2]MCP-2-one 7 were isolated. This indicated that [2n]CPs with large rings; [3.3.3]PCP-2,11,20-trione 20 gave
the reaction was proceeding in a stepwise manner. This [2.2.2]PCP 21[22] (39%) after 20 h of irradiation. However,
method was also applicable to the synthesis of [2.2]pyridin- [3.3.3](1,3,5)CP-2,11,20-trione 22 was inert to the reaction
ophane 9 (56%), but longer irradiation times than those re- and formation of 23 was not observed, whereas monoke-
quired for the treatment of 5 were necessary. Treatment of tone 24[23] provided [3.3.2](1,3,5)CP 25 (34%). This sug-
[3.3]metaparacyclophane(MPCP)-2,11-dione 11 proceeded gested the quenching of the photoexcited state of a carbonyl
smoothly to give [2.2]MPCP 12 (94%). [3.3]PCP-2,11-dione group by neighboring ground-state carbonyl groups in 22.
14 was the most reactive of the [3.3]CP-2,11-diones, and
We can confidently say that the reaction conditions can
afforded [2.2]PCP 15 (97%) after 30 min of irradiation. Ben- be adjusted to the preferential formation of [3.2]CP-2-one
zene may be replaced with other solvents such as ethyl acet- 3 by control of the time spent irradiating 1. As described
ate. This reaction was successfully applied to functionalized above, [3.2]MCP-2-one 7 was isolated in 57% yield after 4
[2.2]CPs, as exemplified by the synthesis of 7,15-di-tert-bu- h of irradiation, together with [2.2]MCP 6 (9%). Similarly
2488
Eur. J. Org. Chem. 2001, 2487Ϫ2499

[2.2]Cyclophanes and [3.2]Cyclophanes from [3.3]Cyclophane-2,11-diones
FULL PAPER
the [3.2]pyridinophan-2-one 10 was obtained in 72% yield stable conformations in solution, aryl ring inversion, and
after 4 h of irradiation, with 16% recovery of 8. [3.2]MPCP- some crystal structures of the [3.2]MCPs. Deuterium atoms
2-one 13 (46%) and [3.2]PCP-2-one 16 (21%) were obtained were introduced into the 2-positions of the trimethylene
1
together with their corresponding [2.2]CPs after 40 min and bridge of [3.2]CPs to simplify the H NMR signals.[30b]
20 min of irradiation, respectively. In addition, this method
is also applicable to the synthesis of [2n]CPs as host molec- [3.2]Metacyclophanes
ules and multilayered [2.2]MCPs.[24]
The intramolecular nature of this reaction was corrobor-
ated by the exclusive formation of unsymmetrical [2.2]CPs
and [3.2]CPs from unsymmetrical starting ketones, as dem-
The most stable conformation of [3.3]MCP, both in the
solid state[29,38] and in solution, is syn(chair-chair)
26a.[29,30b] The order of relative thermodynamic stability of
the three conformers with the syn geometry is: chair-chair
onstrated by 8 and 11. This reaction also proceeds in a step-
26a, chair-boat 26b, and boat-boat 26c. The anti isomers
wise manner. Experimental results show that the preferen-
26d, however, are predicted to be much less stable than the
tial formation of [3.2]CP-2-one 3 from the time-controlled
reaction of 1 is effective when the reaction is slow, as it is
the case of the metacyclophane. Photochemical excitation
of the nǞπ* bands of the dione 1 may first generate a
benzyl radical after the release of CO, followed by intramo-
lecular recombination of the diradical to give 3. A similar
syn conformers, by more than 7 kcal/mol[29,39] on the basis
of MM3 and semiempirical MO calculations.[29,39,40] Of the
three syn conformers, only 26a is observed by low-temper-
1
ature H NMR spectroscopy.[29,30b] The observed temper-
ature dependence in the VT 1H NMR spectrum of 26
(∆G϶ ϭ 11.6 kcal/mol, CD2Cl2) is attributable to the
photochemical cleavage of the remaining ϪCH2COCH2Ϫ
bridge-flipping process,[30b,39] the ∆G϶ value of which is
bridge, involving the formation of the benzyl radical and
much higher than that of the aryl ring inversion pro-
subsequent intramolecular recombination of the diradical,
cess[30b] (Scheme 2).
may afford [2.2]CP 2.
The advantage of our photochemical method over
Vögtle’s method[17] and other conventional methods[10Ϫ16]
is the simple and easy experimental procedures (which do
not require special apparatus) and the high yields. Thus,
[3.3]CP-2,11-diones 1, which are readily accessible by
TosMIC coupling,[8] serve as common precursors not only
for the synthesis of [3.3]CPs 4, but also for [2.2]CPs and
[3.2]CPs 2 and 3. This method provides an alternative syn-
thetic route to [2.2]CPs, and a general synthetic method
for [3.2]CPs.
A Conformational Study of [3.2]Metacyclophanes
Ten-membered [2.2]CPs are generally rigid and no dy-
namic behavior is observed at ambient temperatures in so-
lution,[25,26,9] whereas [3.3]CPs are mobile at ambient tem-
peratures,[25] and chair-boat-type flipping of the trimethy-
lene bridges can be observed by variable-temperature
(VT) 1H NMR spectroscopy in [3.3]PCPs[27,28] and
[3.3]MCPs,[2,29Ϫ32] as well as in multi-bridged [3n]CPs.[33,34]
In the [3.3]MCPs, the inversion of the aryl ring is also re-
sponsible for the conformational isomerism, but the energy
barrier (∆G϶) for this process is much lower than that for
the bridge flipping (11Ϫ12 kcal/mol) and cannot be de-
1
tected by the VT H NMR method.[30b] In contrast, the
Scheme 2. Possible conformers of [3.3]metacyclophane 26, and its
conformational isomerism by chair-boat-type flipping of the trime-
aryl ring inversion process in the 11-membered [3.2]CPs is
thylene bridges and aryl ring inversion
1
amenable to study by the VT H NMR method; Griffin et
al. reported that the ∆G϶ values for the aryl ring inversion
In contrast, the preferred conformation of [3.3]MCP-
lie between 16 and 19 kcal/mol, and were dependent upon 2,11-dione 5 is anti, as gauged by the strongly shielded inner
the steric nature of the 2-substituent in a series of 2-substi- aromatic protons (Hi: δ ϭ 5.78 in CDCl3), while the signals
tuted [3.2]MCPs.[35] Sato et al. reported that an increase of of the corresponding protons (Hi) of 26 appear at δ ϭ 6.80
1
∆G϶ in 2-thia[3.2]MCP was observed in the sequence going in CDCl3. The dione 5 showed no H NMR spectroscopic
from sulfide to sulfoxide, and then sulfone.[36] Krois and temperature dependence down to Ϫ90 °C in CD2Cl2, sug-
Lehner reported that the ∆G϶ value of the parent [3.2]MCP gesting energy barriers for the flipping of bridges and inver-
27 was 17.4 kcal/mol (Tc ϭ 90 °C) in perchlorobutadiene[37] sion of aryl rings much lower than those in 26. The X-ray
1
in the VT H NMR study of a series of [m.n]MCPs (m ϭ structural analysis shows that 5 adopts anti geometry and
3, 4; n ϭ 2, 3). Here we describe further information on the two carbonyl groups take antiparallel arrangement. The syn
Eur. J. Org. Chem. 2001, 2487Ϫ2499
2489

T. Shinmyozu et al.
FULL PAPER
and anti geometries 5 are of comparable thermodynamic are listed in Table 2. CarbonϪcarbon and carbonϪoxygen
stability, and the antiparallel arrangement of the two car- bond lengths and angles agree well with normal values. The
bonyl groups stabilizes the molecule because of the cancel- two benzene rings are parallel, and only the C(9) and C(9*
lation of dipole moments. Of the conformers with the anti ) atoms are overlapped. This suggests that the two benzene
geometry, 5c would be expected to be the most stable, with rings can interact only through π-orbitals at the C(9) and
the isomers with twist-boat-like and boat-boat-like con- C(9*) atoms. The transannular distances between C(9) and
˚
formations 5a and 5b less stable than 5c by 3.3 and 1.0 kcal/ C(9*) and between C(8) and C(4*) are 2.99 and 3.31 A,
mol, respectively, on the basis of AM1 calculations (Fig- respectively. The benzene ring is slightly distorted towards
ure 1). The twist-boat-like conformation 5a, however, was the boat form; the dihedral angles between the
observed in the crystal structure of anti-[3.3]MCP quinhyd- C4ϪC5ϪC7ϪC8 and C4ϪC9ϪC8 planes and the
rone dimethyl ether.[30c]
C4ϪC5ϪC7ϪC8 and C5ϪC6ϪC7 planes are 3.47 and
1.34°, respectively. Crystal-packing diagrams show that the
structure contains two separate molecules per unit cell. It
˚
should be noted that the intermolecular distances (2.55 A)
between the carbonyl oxygen atom O(1) and the proton
H(3) at the benzylic positions of a neighboring molecule
are shorter than the sum of van der Waals radii[41] of a
˚
˚
hydrogen atom (1.20 A) and an oxygen atom (1.40 A) and
therefore an attractive interaction through intermolecular
hydrogen bonding is to be expected (Figure 3).
2,2-Dideuterio[3.2]MCP 27-D2 shows the following aro-
matic 1H NMR signals (270 MHz, CDCl3, 20 °C): δ ϭ 5.19
(s, 2 H, H-9), 6.8Ϫ6.9 (2 d, 4 H, H-5 and H-7), and 7.12 (t,
J ϭ 7.59 Hz, 2 H, H-6). The strongly shielded internal aro-
matic protons (H-9) show the preferred geometry to be anti,
and this is in sharp contrast to that of [3.3]MCP 26. Con-
formational isomerism between anti-27 and anti-27Ј
through syn-27 is therefore to be expected (Scheme 3).[35,37]
MM3 and PM3 calculations predicted that anti-27 should
be more stable than syn-27 by 2.8 and 1.1 kcal/mol, respect-
ively.
Figure 1. Stable anti conformers of [3.3]metacyclophane-2,11-dione
5 and their relative heats of formation [∆∆Hf (kcal molϪ1), AM1],
based on 5c
Figure 2 shows the molecular structure of 5 in the crys-
talline state at Ϫ180 °C. The ORTEP drawings A (top view)
and B (side view) show that the two benzene rings assume
1
The H NMR signals due to both bridge protons dis-
an anti geometry, with the two carbonyl groups of the played strong temperature-dependence phenomena, while
bridges in an anti-parallel arrangement. The crystal data the aromatic proton signals were almost intact. At 24 °C in
Figure 2. ORTEP drawings A (top view) and B (side view) of [3.3]metacyclophane-2,11-dione 5, with bond angles [°] and bond lengths
˚
[A] (Ϫ180 °C)
2490
Eur. J. Org. Chem. 2001, 2487Ϫ2499

[2.2]Cyclophanes and [3.2]Cyclophanes from [3.3]Cyclophane-2,11-diones
Table 2. Summary of crystallographic data and refinement details
FULL PAPER
Compound
5
7
27
10
28
29
Empirical formula
Molecular mass
Crystal color, habit
Crystal size [mm]
Crystal system
C18H16O2
264.32
C17H16O1.27
240.63
C17H20
224.35
C16H15NO
237.30
C16H17N
223.32
C18H22S2N
316.50
colorless, prism colorless, prism colorless, prism colorless, prism colorless, prism colorless, platelets
0.2 ϫ 0.3 ϫ 0.2 0.9 ϫ 0.5 ϫ 0.3 0.3 ϫ 0.8 ϫ 0.8 0.8 ϫ 0.6 ϫ 0.8 0.6 ϫ 0.8 ϫ 0.8 0.50 ϫ 0.02 ϫ 0.50
monoclinic
P21/n (no. 14)
Ϫ180Ϯ1
7.635(6)
5.535(2)
15.583(9)
monoclinic
P21/n (no. 14)
23Ϯ1
7.874(3)
14.448(6)
11.426(4)
orthorhombic
orthorhombic
orthorhombic
monoclinic
Space group
P212121 (no. 19) P212121 (no. 19) P212121 (no. 19) P21/c (no. 14)
23Ϯ1
11.644(3)
14.063(4)
7.679(2)
Temperature [°C]
23Ϯ1
15Ϯ1
Ϫ180Ϯ1
˚
a [A]
14.68(4)
22.13(4)
7.89(4)
11.639(4)
14.144(5)
7.71(1)
7.0404(2)
17.7631(4)
12.0506(4)
˚
b [A]
˚
c [A]
α [°]
β [°]
γ [°]
93.933(1)
94.57(4)
91.8264(8)
3
˚
V [ A ]
Z
657.00
2
1.336
280
0.86 (Mo)
55 (Mo)
1295.7(9)
4
1.233
513
0.76 (Mo)
55 (Mo)
1257.5(6)
4
1.185
488
0.66 (Mo)
55 (Mo)
2564(12)
8
1.229
1008
0.76 (Mo)
55 (Mo)
1268.8
4
1.169
480
0.68 (Mo)
55 (Mo)
1506.27(7)
4
1.396
676
3.46 (Mo)
55 (Mo)
Dcalcd. [g cm3]
F(000)
µ(Mo-Kα) [cmϪ1
2θmax [°]
]
No. of reflections:
measured
independent
1348
1348
Ϫ
3115
2973
0.033
1217
1686
1686
Ϫ
3356
3351
0.033
1805
1181
1181
Ϫ
13840
3447
0.029
2850
Rint
No. of observations
[I Ͼ 3.00σ(I)]
No. of parameters
1219
630
764
124
172
172
355
154
267
Reflection/parameter ratio 9.83
7.08
0.089
0.070
4.38
0.05
0.24
3.66
0.048
0.035
2.69
0.98
0.09
5.08
0.055
0.048
2.94
0.98
0.20
4.96
0.068
0.064
5.18
0.43
0.17
10.67
0.031
0.052
1.25
0.002
0.26
R
Rw
GoF
0.044
0.045
1.09
Max. ∆/σ
0.00
0.21
Max. ∆ρ [e/nmϪ3
]
Figure 3. The crystal-packing diagram of [3.3]metacyclophane-
2,11-dione 5
[D5]bromobenzene, the benzylic proton signals of the
ϪCH2CD2CH2Ϫ bridge appeared as an AB system [δ ϭ
2.24 (d, J ϭ 13.5 Hz, 2 H, Hax) and 2.62 (d, J ϭ 14.2 Hz,
2 H, Heq)], whereas the ethano bridge protons showed an
A2X2 system [δ ϭ 2.08 (d, J ϭ 7.59 Hz, 2 H), 2.88 (d, J ϭ
7.26 Hz, 2 H) analyzed as an AB approximation (Figure 4)].
This indicated that the molecule was frozen in an anti con-
Scheme 3. Conformational isomerism of [3.2]metacyclophanes by
an aryl ring inversion process
formation at this temperature. The AB system gradually ponding to this spectral change, the A2X2 signal also co-
broadened with increasing temperature, coalesced at 62 °C, alesced at ca. 80 °C and became a sharp singlet above 140
and finally became a sharp singlet above 100 °C. Corres- °C. The energy barrier (∆G϶) for the ring-inversion process
Eur. J. Org. Chem. 2001, 2487Ϫ2499
2491

T. Shinmyozu et al.
FULL PAPER
Figure 4. VT 1H NMR spectra of the bridge proton signals of 2,2-
dideuterio[3.2]metacyclophane 27-D2 in [D5]bromobenzene
(270 MHz)
Figure 5. VT 1H NMR spectra of the bridge proton signals of
[3.2]metacyclophane-2-one 7 in [D5]bromobenzene (270 MHz)
was estimated to be 15.5 kcal/mol (Tc ϭ 62 °C), based on
the AB system.[42]
1
In the VT H NMR spectrum of [3.2]MCP-2-one 7, AB
and A2X2 signals were observable separately. At 23 °C in
[D5]bromobenzene, the aromatic proton signals appeared at
δ ϭ 5.06 (s, H-9), 6.9Ϫ7.0 (2 d, 4 H, H-5 and H-7), and
7.13 (t, J ϭ 7.59 Hz, H-6), and the bridge proton signals
appeared as an AB [δ ϭ 3.33 (d, J ϭ 14.5 Hz, Hax), 3.38
(d, J ϭ 14.5 Hz, Heq)] and an A2X2 system [δ ϭ 2.02 (d,
J ϭ 7.92 Hz, 2 H,), 2.84 (d, J ϭ 7.92 Hz, 2 H) analyzed as
ated to be 16.9 kcal/mol (Tc ϭ 74 °C), based on the AB
system, a value slightly larger than that of the parent
[3.2]MCP 27.[43] The corresponding ∆G϶ value in
[D6]DMSO was 16.6 kcal/mol (Tc ϭ 70 °C) and so no solv-
ent effect was observed.[44]
The crystal structure of 27 shows that the two benzene
an AB approximation]. These data also indicated that the rings are almost parallel irrespective of the different lengths
molecule was fixed in an anti conformation at this temper- of the bridges (Figure 6), and they overlap at only one posi-
ature, and so a similar interconversion between anti-7 and tion: at C(9) and C(17). However, the structure could not
anti-7Ј through syn-7 was to be expected (Scheme 3). The be considered in detail because of disorder problems, even
benzylic proton signals of both bridges exhibited significant at Ϫ160 °C. Rather similarly to those in the crystal struc-
temperature-dependence phenomena (Figure 5). The AB ture of 27, the two benzene rings of 7 are almost parallel
˚
˚
system (Hax and Heq) coalesced at 74 °C, while the A2X2 [C(4)ϪC(16) 3.29 A, C(8)ϪC(12) 3.08 A] and overlap at
signal coalesced at 117 °C and became a broad singlet at only one position, at C(9) and C(17) (Figure 7); the situ-
140 °C. The exchange of both benzylic proton signals cle- ation is also similar in [3.3]MCP-2,11-dione 5, although the
˚
arly indicated the presence of the benzene ring inversion transannular distance between C(9) and C(17) (2.82 A) is
process, the ring-inversion ∆G϶ value of which was estim- shorter than that in 5 (2.99 A). Thus, 7 adopts an almost
˚
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[2.2]Cyclophanes and [3.2]Cyclophanes from [3.3]Cyclophane-2,11-diones
FULL PAPER
but the ∆G϶ value for the aryl ring inversion process should
be smaller than that in 27 (Scheme 3) because of the smaller
steric bulkiness of the lone pair electrons of a nitrogen atom
in comparison with a hydrogen atom.
In [3]metacyclo[2](2,6)pyridinophane-2-one 10, two dif-
ferent conformers, anti-trans and anti-cis, are to be ex-
pected, depending on the orientation of the carbonyl group
(Scheme 4). The term ‘‘anti’’ refers to an anti geometry of
the aromatic rings, while the term ‘‘cis’’ denotes that the
carbonyl group is directed toward the pyridine ring, the
other isomer being termed as trans. In this compound, two
types of conformational isomerism are conceivable: inver-
sion of the aryl ring (Scheme 3) and flipping of the three-
carbon bridge (Scheme 4).
Figure 6. ORTEP drawing of [3.2]metacyclophane 27
Scheme 4. The three-carbon bridge flipping between anti-trans
(10a) and anti-cis (10b)
At 24 °C in [D5]bromobenzene, the chemical shifts of the
internal aromatic proton signal H-9 (δ ϭ 5.18, s) and the
external aromatic proton signals H-6 (δ ϭ 7.18, t, J ϭ
7.59 Hz) and H-14 (δ ϭ 7.23, t, J ϭ 7.59 Hz) suggested
that the preferred conformation was anti, as in the case of
[3.2]MCP-2-one 7. The benzylic proton signals of the three-
carbon bridge appeared as a pair of broad singlets at 24 °C,
and this suggested that the bridge was mobile even at this
temperature. In contrast, the ethano bridge protons showed
a pair of broad signals at 24 °C, with the signals gradually
sharpening as the temperature increased and coalescing at
34 °C (Tc) (Figure 8). Using the ethano bridge protons as a
basis,[45] the ∆G϶ value for the aryl ring inversion was es-
timated to be ca. 14 kcal/mol, which was lower than that in
[3.2]MCP-2-one 7 (16.9 kcal/mol). Each singlet signal (20
°C, CD2Cl2) arising from the benzylic protons of the three-
carbon bridge split into an AB quadruplet below ca. Ϫ30
°C, indicating that the bridge flipping (Scheme 4) was
frozen below ca. Ϫ30 °C (Figure 8).
Interestingly, two conformers, anti-cis and anti-trans,
were observed in the crystal structure of 10 (Figure 9). This
indicated that even flipping of the three-carbon bridge was
frozen in the solid state. The top views of the two con-
formers are similar, but the inclination of the pyridine ring
in the two conformers is different (Figure 10). The transan-
nular distance between N-2 and C-25 in the anti-trans con-
Figure 7. X-ray structure of [3.2]metacyclophane-2-one 7: A and B
(side views) and C (top view)
˚
former (2.64 A) is shorter than the corresponding distance
˚
(N-1ϪC-9) in the anti-cis conformer (2.78 A). Another in-
parallel arrangement of the benzene rings and their trans- teresting feature is that the pyridine ring is slightly inclined
annular distances are slightly shorter than those in 5.
when the facing benzene ring is situated in the plane, as is
to be expected from the unsymmetrical bridge lengths. This
is in sharp contrast to the crystal structures of [3.2]MCPs
[3]Metacyclo[2](2,6)pyridinophanes
A similar conformational isomerism to that of [3.2]MCP 7 and 27 and [3]metacyclo[2](2,6)pyridinophanes 28 and 29,
27 is to be expected for [3]metacyclo[2](2,6)pyridinophanes, in which the two aromatic rings are almost parallel irre-
Eur. J. Org. Chem. 2001, 2487Ϫ2499
2493

T. Shinmyozu et al.
FULL PAPER
Figure 9. ORTEP drawings of [3]metacyclo[2](2,6)pyridinophane-
2-one 10; two independent molecules [anti-cis (10b) and anti-trans
(10a)] are observed; top views (top) and side views (bottom)
Figure 8. VT 1H NMR spectra of the bridge proton signals of
[3]metacyclo[2](2,6)pyridinophane-2-one 10 in [D5]bromobenzene
(24 to 120 °C) and CD2Cl2 (20 to Ϫ80 °C) (270 MHz)
Figure 10. X-ray structures and distortion angles of the aromatic
rings of anti-cis (10b) and anti-trans (10a) of [3]metacyclo[2](2,6)-
pyridinophane-2-one 10
spective of the different lengths of the bridges. The benzene
rings are more deformed than the pyridine rings (Fig-
ure 10). Figure 11 shows the crystal-packing diagram of 10.
In the VT 1H NMR spectrum of 2,2-dideuterio[3]metacy-
clo[2](2,6)pyridinophane 28-D2 in CD2Cl2, the benzylic 3.19 [C(8)ϪC(12)], and 3.24 A [C(4)ϪC(16)]. The distances
proton signals of both bridges displayed significant temper- are shorter than the corresponding distances in 7 by ca. 0.1
˚
˚
ature-dependence phenomena (Figure 12). The two sets of A (Figure 13). The ORTEP drawing of 2-dithiabutanediyl-
AB and AAЈXXЈ signals were clearly observed at Ϫ50 °C, [3]metacyclo[2](2,6)pyridinophane 29 is shown in Figure 14.
and each signal gradually broadened as the temperature The two aryl rings are almost parallel and overlap only at
was increased, finally becoming a broad signal at ca. 20 N(1) and C(9) positions, with the transannular distance be-
°C. Although the accurate ∆G϶ value for the pyridine ring ing 2.717 A. The three-carbon bridge adopts a twist-boat-
˚
inversion was difficult to determine, it was expected to be like conformation.
much smaller than that of [3.2]MCP 27.[46]
As in the structures of [3.2]MCPs 27 and 7, the two aro-
The ∆G϶ values for the aryl ring inversion of the
matic rings are almost parallel in the crystalline state. The [3.2]MCPs are in the range of 14 to 17 kcal/mol, and the
two aryl rings overlap only at the N-1 and C-9 positions, value for the pyridine ring inversion is slightly smaller than
with the transannular distances being 2.72 [N(1)ϪC(9)], that of the benzene ring.
2494
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[2.2]Cyclophanes and [3.2]Cyclophanes from [3.3]Cyclophane-2,11-diones
FULL PAPER
Figure 11. Crystal packing diagram of [3]metacyclo[2](2,6)-
pyridinophane-2-one 10
Figure 12. VT 1H NMR spectra of the bridge proton signals of
2,2-dideuterio[3]metacyclo[2](2,6)pyridinophane 28-D2 in CD2Cl2
(270 MHz)
Conclusion
5. In the crystal structure of 10, two conformers (anti-trans
and anti-cis) are observed.
The significance of the photodecarbonylation reaction
lies in the fact that a series of [3.3]CPs, [3.2]CPs, and
[2.2]CPs can be prepared from the same starting compound
1. The method may therefore be most conveniently used
when a series of [3.3]CPs, [3.2]CPs, and [2.2]CPs is required.
In sharp contrast to [3.3]MCP 26 and its dione 5, the aryl
ring inversion processes in [3.2]MCPs 27, 7, 28, and 10 were
Several new [3.2]CPs, such as [3]metacyclo[2](2,6)pyridin-
ophanes 10, 28, 29 and [3.2]MPCP-2-one 13, were obtained
as racemic mixtures and interesting chiroptical properties
are to be expected for their individual enantiomers.[47] Res-
olutions of the racemic mixtures are in progress and the
results will be reported elsewhere.
1
amenable to study by the VT H NMR method, and the
energy barriers were estimated to be 14Ϫ17 kcal/mol. The
barriers in [3]metacyclo[2](2,6)pyridinophanes 28 and 10
were slightly lower than those in [3.2]MCPs 27 and 7, due
to the lower steric bulkiness of the pyridine ring nitrogen
atom lone pair in comparison with that of a hydrogen atom.
Quite interestingly, the two aryl rings of [3.2]MCPs 27
and 7 and [3]metacyclo[2](2,6)pyridinophanes 28 and 29 are
almost parallel in spite of the unsymmetrical bridge lengths,
whereas the pyridine ring of [3]metacyclo[2](2,6)pyridino-
phane-2-one 10 is slightly inclined. In all [3.2]MCPs, two
aryl rings overlap only at one position, and the transannu-
Experimental Section
General: Melting points: Yanaco micro melting point apparatus
MP-S3. Ϫ High-pressure Hg lamp: Shigemi Standard Shoji
AHH400S (400 W). Ϫ NMR: JEOL JNM-EX 270 or JEOL JNM-
AL300. CDCl3 as solvent unless otherwise noted, TMS as internal
standard. Ϫ FAB-MS: JEOL JMS-HX 110A (m-nitrobenzyl alco-
hol). Ϫ UV/Vis: Hitachi U-3500. Ϫ IR: Hitachi Nicolet I-5040 FT-
IR. Ϫ Elemental analysis: Service Center for the Elementary Ana-
lysis of Organic Compounds affiliated with the Faculty of Science,
Kyushu University. Ϫ Analytical thin layer chromatography (TLC)
lar distances are shorter than those of [3.3]MCP-2,11-dione and column chromatography were performed on 60 F254 silica gel
Eur. J. Org. Chem. 2001, 2487Ϫ2499 2495

T. Shinmyozu et al.
FULL PAPER
Figure 14. ORTEP drawings of 2-dithiabutanediyl[3]metacyclo[2]-
(2,6)pyridinophane 29 (Ϫ180 °C): (A) top view and (B) side view
with N2, was irradiated with a high-pressure Hg lamp as the in-
ternal light source at ambient temperatures while N2 was bubbled
through the solution. Progress of the reaction was monitored by
TLC (silica gel, CH2Cl2). After 9.5 h of irradiation, the solvent was
removed in vacuo, and the residue was purified using a short col-
umn of silica gel with CH2Cl2 to give 6 (83 mg, 98%, Rf ϭ 0.83)
as a white solid. When the reaction was carried out on a larger
scale (5, 1.06 g, 4.0 mmol), 95% yield of 6 (792 mg) was obtained
after 20 h of irradiation. Ϫ 1H NMR: δ ϭ 2.10 (AAЈ, 4 H,
ϪCH2CH2Ϫ), 3.10 (XXЈ, 4 H, ϪCH2CHϪ), 4.27 (s, 2 H, ArH),
7.05 (dd, J ϭ 7.3, 1.7 Hz, 4 H, ArH), 7.28 (t, J ϭ 7.6 Hz, 2 H,
ArH) [ref.[55] (CCl4): δ ϭ 2.03 (AAЈ, 4 H, ϪCH2CHϪ), 3.09 (XXЈ,
4 H, ϪCH2CH2Ϫ), 4.25 (s, 2 H, ArH), 7.03 (m, 4 H, ArH), 7.25
(t, J ϭ 7.8 Hz, 2 H, ArH)].
Figure 13. X-ray structure of [3]metacyclo[2](2.6)pyridinophane 28
(Merck) and 60 silica gel (Merck, 40Ϫ63 µm), respectively. Ϫ Ben-
zene was used without further purification. Xylene was distilled
from CaH2. [3.3]MCP-2,11-dione 5,[48a] [3.3]MPCP-2,11-dione
11,[8a] [3]metacyclo[3](2,6)pyridinophane-2,11-dione 8,[8b] [3.3]PCP-
2,11-dione
14,[48b]
[3.3.3]PCP-2,11,20-trione
20,[8a]
and
[3.3.3](1,3,5)CP-2,11,20-trione 22,[33a] and [3.3.2](1,3,5)CP-2-one
24,[23] were prepared according to literature procedures. nBu3SnD
was prepared by LiAlD4 reduction of nBu3SnCl in Et2O.[49]
X-ray Crystallographic Study: All measurements were made with
a Rigaku RAXIS-IV imaging plate area detector with graphite-
monochromated Mo-Kα radiation and a rotating anode generator.
The crystal structure was solved by direct methods [SIR88[50] (5),
SHELXS86[51] (7), SIR92[52] (10, 27, 28, 29)] and expanded using
Fourier techniques [DIRDIF94[53]]. The non-hydrogen atoms were
refined anisotropically, and hydrogen atoms were refined iso-
topically. All the computations were performed using the teXsan
program.[54] Crystallographic data (excluding structure factors) for
the structures reported in this paper have been deposited with the
Cambridge Crystallographic Data Centre as supplementary pub-
lications no. CCDC-116788 (10), -116789 (5), -116790 (28), and -
116791 (27), -116792 (7), and -149324 (29). Copies of the data can
be obtained free of charge upon request to CCDC, 12 Union Road,
Cambridge CB2 1EZ, UK [Fax: (internat.) ϩ 44-1223/336-033;
E-mail: deposit@ccdc.cam.ac.uk].
[3.2]Metacyclophane-2-one (7): A benzene solution (500 mL) of 5
(600 mg, 2.27 mmol) was irradiated for 4 h as described for 6. The
reaction mixture was concentrated to dryness, and the residue was
separated by column chromatography (SiO2, toluene) to give 7
(307 mg, 57%, Rf ϭ 0.39), along with 6 (87 mg, 9%) and recovered
5 (389 mg). Ϫ 7: Colorless crystals (hexane), m.p. 111Ϫ112 °C. Ϫ
1H NMR: δ ϭ 2.21 (AAЈ, 2 H, ϪCH2CH2Ϫ), 3.09 (XXЈ, 2 H,
ϪCH2CH2Ϫ), 3.47 (d, J ϭ 14.9 Hz, 2 H, ϪCH2COCH2Ϫ), 3.55
(d, J ϭ 14.9 Hz, 2 H, ϪCH2COCH2Ϫ), 5.21 (s, 2 H, ArH, H-9),
7.12Ϫ7.15 (m, 4 H, ArH, H-6 ϩ H-7), 7.31 (d, J ϭ 7.26 Hz, 2 H,
ArH, H-5). Ϫ IR (KBr): ν ϭ 1698 (ϪCO) cmϪ1. Ϫ FABMS:
˜
m/z ϭ 236 [Mϩ]. Ϫ C17H16O (236.3): calcd. C 86.40, H 6.82; found
C 86.35, H 6.90.
[2.2]Metacyclophane (6):
A
benzene solution (500 mL) of
[3.2]Metacyclophane (27): A mixture of the ketone 7 (132 mg,
[3.3]MCP-2,11-dione 5 (106 mg, 0.40 mmol), flushed for 30 min
0.56 mmol), hydrazine hydrate (100%, 2 mL), KOH (500 mg), and
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[2.2]Cyclophanes and [3.2]Cyclophanes from [3.3]Cyclophane-2,11-diones
FULL PAPER
diethylene glycol (30 mL) was heated at ca. 130 °C for 3 h and then
at ca. 200 °C for 3 h. After cooling, the mixture was poured into
(10:1)] to give 10 (485 mg, 72%, Rf ϭ 0.51) as colorless crystals. Ϫ
10: Colorless plates (CH2Cl2/hexane), m.p. 121Ϫ122 °C. Ϫ 1H
dilute aqueous HCl solution and extracted with Et2O. The com- NMR: δ ϭ 2.5 (br s, 2 H, ϪCH2CH2Ϫ), 3.2 (br s, 2 H,
bined extracts were washed with brine, dried with MgSO4, and fil- ϪCH2CH2Ϫ), 3.61 (s, 2 H, ϪCH2COCH2Ϫ), 3.71 (s, 2 H,
tered, and the filtrate was concentrated to dryness. The residue was ϪCH2COCH2Ϫ), 5.32 (s, 1 H, ArH), 7.10Ϫ7.22 (m, 4 H, ArH,
purified by column chromatography (SiO2, hexane) to give
[3.2]MCP 27 as colorless crystals (113 mg, 91%, Rf ϭ 0.35), m.p.
PyH), 7.36 (t, J ϭ 7.6 Hz, 1 H, ArH), 7.60 (t, J ϭ 7.6 Hz, 1 H,
PyH). Ϫ IR (KBr): ν˜ ϭ 1698 (CO) cmϪ1. Ϫ FABMS: m/z ϭ 237
55Ϫ56 °C (ref.[56] 59Ϫ61 °C). Ϫ 1H NMR: δ ϭ 2.17 (AAЈ, 2 H, [Mϩ]. Ϫ C16H15NO (237.3): calcd. C 80.98, H 6.37, N 5.90; found
ϪCH2CH2Ϫ), 3.04 (XXЈ, 2 H, ϪCH2CH2Ϫ), 1.94 (m, 2 H, C 80.81, H 6.46, N 5.94.
ϪCH2CH2CH2Ϫ), 2.35 (m, 2 H, ϪCH2CH2 CH2Ϫ), 2.77 (m, 2 H,
ϪCH2CH2CH2Ϫ), 5.09 (s, 2 H, ArH, H-9), 6.9Ϫ7.1 (m, 4 H, H-5
[3]Metacyclo[2](2,6)pyridinophane (28): A mixture of 8 (220 mg,
0.93 mmol), hydrazine hydrate (100%, 4 mL), KOH (1.0 g), and di-
ethylene glycol (25 mL) was heated at ca. 130 °C for 2 h and then
and H-7), 7.23 (t, J ϭ 7.3 Hz, 2 H, H-6) [ref.[55]: δ ϭ 2.16 (AAЈ, 4
H, ϪCH2CH2Ϫ), 3.03 (XXЈ, 2 H, ϪCH2CH2Ϫ), 1.93 and 2.32
(A2B2C2, 6 H, ϪCH2CH2CH2Ϫ), 5.09 (s, 2 H, ArH), 7.00Ϫ7.22
at ca. 200 °C for 2 h. After cooling, the reaction mixture was di-
(m, 6 H, ArH)].
luted with water and the mixture was extracted with Et2O. The
combined extracts were washed with brine, dried with MgSO4, and
filtered, and the filtrate was concentrated to dryness. The residue
was passed through a short silica gel column with CH2Cl2/AcOEt
[Rf ϭ 0.79, CH2Cl2/AcOEt (5:1)], and the eluate was concentrated
to dryness to give 28 as colorless crystals (200 mg, 97%). Ϫ 28:
Colorless plates (CH2Cl2/hexane), m.p. 85Ϫ86 °C (decomp.). Ϫ 1H
NMR: δ ϭ 2.01 (m, 2 H, ϪCH2CH2CH2Ϫ), 2.5Ϫ3.2 (m, 8 H,
ϪCH2CH2Ϫ, ϪCH2CH2CH2Ϫ), 5.70 (s, 1 H, H-9), 6.90Ϫ6.93 (m,
4 H, H-5, H-7, H-13, H-15), 7.10 (t, J ϭ 7.59, 7.26 Hz, 1 H, H-6),
7.44 (t, J ϭ 7.59 Hz, 1 H, H-14). Ϫ EIMS: m/z ϭ 223 [Mϩ]. Ϫ
C16H17N (223.3): calcd. C 86.05, H 7.67, N 6.27; found C 85.95,
H 7.63, N 6.25.
2,2-Dideuterio[3.2]metacyclophane (27-D2): Compound 7 (211 mg,
0.89 mmol) was dissolved in AcOH (10 mL) and 1,2-ethanedithiol
(1 mL, 12 mmol) and 10 drops of BF3·OEt2 were added in succes-
sion. The mixture was stirred for 38 h at room temperature. The
reaction was quenched by the addition of water and the mixture
was extracted with CH2Cl2. The combined organic extracts were
washed with saturated aqueous NaHCO3 solution, dried with
MgSO4, and filtered. The filtrate was concentrated to dryness in
vacuo to give 2-dithiabutanediyl[3.2]MCP as colorless crystals
[264 mg, 94%, Rf ϭ 0.86 (SiO2, toluene)]. A sample was crystallized
from CH2Cl2/hexane, m.p. 172Ϫ174 °C (decomp.). Ϫ 1H NMR:
δ ϭ 2.23 (AAЈ, 2 H, ϪCH2CH2Ϫ), 3.03 (XXЈ, 2 H, ϪCH2CH2Ϫ),
2.72 (d, J ϭ 14.9 Hz, 2 H, ϪCH2CCH2Ϫ), 3.52 (d, J ϭ 14.5 Hz, 2
H, ϪCH2CCH2-), 3.2Ϫ3.4 (m, 2 H, ϪSCH2CH2SϪ), 3.4Ϫ3.6 (m,
2 H, ϪSCH2CH2SϪ), 4.89 (s, 2 H, ArH), 7.09 (d, J ϭ 7.3 Hz, 2
H, ArH), 7.26 (t, J ϭ 7.6 Hz, 2 H, ArH), 7.62 (d, J ϭ 7.6 Hz, 2
H, ArH). Ϫ FABMS: m/z ϭ 312 [Mϩ]. Ϫ C19H20S2 (312.5): calcd.
C 73.03, H 6.45; found C 72.88, H 6.52. Ϫ A mixture of the
thioacetal (105 mg, 0.34 mmol), nBu3SnD (2 mL, 7.4 mmol), AIBN
(50 mg), and xylene (20 mL) was refluxed for 24 h under N2. The
solvent was removed in vacuo and the residue was separated by
preparative TLC (SiO2, hexane, Rf ϭ 0.46) to give 27-D2 (49 mg,
64%). A sample was recrystallized from MeOH at low temperatures
to give colorless crystals, m.p. 59Ϫ60 °C. Ϫ 1H NMR: δ ϭ 2.17
(AAЈ, J ϭ 7.9 Hz, 2 H, ϪCH2CH2Ϫ), 3.04 (XXЈ, J ϭ 7.9 Hz, 2 H,
ϪCH2CH2Ϫ), 2.31 (d, J ϭ 14.2 Hz, 2 H, ϪCH2CD2CH2Ϫ), 2.78
(d, J ϭ 14.2 Hz, 2 H, ϪCH2CD2CH2Ϫ), 5.09 (s, 2 H, H-9),
7.00Ϫ7.03 (m, 4 H, H-5 and H-7), 7.23 (t, J ϭ 7.59 Hz, 2 H, H-
6). Ϫ EIMS: m/z ϭ 224 [Mϩ]. Ϫ C17H16D2 (224.3): calcd. C 91.02,
H 8.09; found C 90.87, H 8.09.
2,2-Dideuterio[3]metacyclo[2](2,6)pyridinophane (28-D2): Com-
pound 10 (146 mg, 0.615 mmol) was dissolved in AcOH (10 mL),
1,2-ethanedithiol (1 mL, 12 mmol) and BF3·OEt2 (0.2 mL) were
added in succession, and the mixture was stirred for 20 h at room
temperature. An additional quantity of BF3·OEt2 (0.2 mL) was ad-
ded and the mixture was stirred for an additional 24 h. The reac-
tion mixture was neutralized by addition of saturated aqueous
NaHCO3 solution and extracted with CH2Cl2. The combined
CH2Cl2 extracts were dried with MgSO4, and filtered. The filtrate
was concentrated in vacuo and the concentrate was separated by
preparative silica gel TLC with CH2Cl2 (Rf ϭ 0.25) to give 2-dithia-
butanediyl[3]metacyclo[2](2,6)pyridinophane 29 (136 mg, 71%). A
sample was recrystallized from AcOEt/CH2Cl2 to give colorless
1
crystals, m.p. 166.5Ϫ167.5 °C. Ϫ H NMR: δ ϭ 2.51 (AAЈ, 2 H,
ϪCH2CH2Ϫ), 3.51 (XXЈ, 2 H, ϪCH2CH2Ϫ), 2.78 (d, J ϭ 14.5 Hz,
1 H, ϪCH2CCH2Ϫ), 3.54 (d, J ϭ 14.5 Hz, 1 H, ϪCH2CCH2Ϫ),
2.98 (d, J ϭ 14.5 Hz, 1 H, ϪCH2CCH2Ϫ), 3.63 (d, J ϭ 14.2 Hz, 1
H, ϪCH2CCH2Ϫ), 2.9Ϫ3.6 (m, 4 H, ϪSCH2CH2SϪ), 4.83 (s, 1 H,
H-9), 7.13 (d, J ϭ 7.3 Hz, 2 H, H-5, H-7), 7.26 (t, J ϭ 7.3 Hz, 1
H, H-6), 7.5Ϫ7.7 (m, 3 H, PyH). Ϫ FABMS: m/z ϭ 314 [M ϩ H]ϩ.
Ϫ C18H19NS2·0.05 CH2Cl2 (after drying at 100 °C in vacuo for 1
d) (317.7): calcd. C 68.23, H 6.06, N 4.41; found C 67.94, H 6.16,
N 4.36. Ϫ A mixture of 29 (68 mg, 0.217 mmol), nBu3SnD (1.5 g,
5.1 mmol), AIBN (50 mg), and xylene (15 mL) was refluxed for
36 h under N2. The solvent was removed in vacuo and the residue
was first separated by preparative silica gel TLC with CH2Cl2. Two
bands were observed, and the lower band was further purified by
[2]Metacyclo[2](2,6)pyridinophane (9): A benzene solution (1 L)
of [3]metacyclo[3](2,6)pyridinophane-2,11-dione 8 (212 mg, 0.8
mmol) was irradiated as described for 6. Progress of the reaction
was monitored by TLC [SiO2, CH2Cl2/AcOEt (5:1), Rf values of 9
and 10 were 0.51 and 0.49]. After 45 h, the solvent was removed in
vacuo and the residue was separated by preparative TLC [Al2O3,
hexane/ether (5:1)] to give 9 (93 mg, 56%) and [3]metacyclo[2](2,6)-
pyridinophane-2-one 10 (26 mg, 14%). Ϫ 9: 1H NMR: δ ϭ
2.25Ϫ2.42 (m,
4 H, ϪCH2CH2Ϫ), 3.13Ϫ3.23 (m, 4 H,
ϪCH2CH2Ϫ), 4.39 (s, 1 H, ArH), 7.07Ϫ7.12 (m, 4 H, ArH), 7.31
(t, J ϭ 7.4 Hz, 1 H, ArH), 7.60 (t, J ϭ 7.6 Hz, 1 H, ArH).
[ref.[57]4.40 (s, 1 H, ArH), 7.05 (d, J ϭ 8 Hz, 2 H, PyH), 7.57 (t,
J ϭ 8 Hz, 1 H, PyH).
silica gel column chromatography [CH2Cl2/AcOEt (10:1), Rf
ϭ
0.27] to give colorless crystals (25 mg, 52%). Ϫ 28-D2: Colorless
granules (CH2Cl2/AcOEt), m.p. 74Ϫ75 °C. Ϫ 1H NMR: δ ϭ
2.5Ϫ3.1 (m, 8 H, ϪCH2CH2Ϫ, ϪCH2CD2CH2Ϫ), 5.70 (s, 1 H, H-
9), 6.9 (m, 4 H, H-5, H-7, H-13, and H-15), 7.10 (t, J ϭ 7.58 Hz,
[3]Metacyclo[2](2,6)pyridinophane-2-one (10): A benzene solution
(500 mL) of 8 (800 mg, 2.84 mmol) was irradiated for 4 h as de- 1 H, H-6), 7.44 (t, J ϭ 7.59 Hz, 1 H, H-14). Ϫ EIMS: m/z ϭ 225
scribed for 6. The solvent was removed in vacuo and the residue
[Mϩ]. Ϫ C16H15D2N (225.4): calcd. C 85.29, H 7.61, N 6.22; found
was purified by column chromatography [SiO2, CH2Cl2/AcOEt
C 85.15, H 7.58, N 6.15.
Eur. J. Org. Chem. 2001, 2487Ϫ2499
2497

T. Shinmyozu et al.
FULL PAPER
[2.2]Metaparacyclophane (12):
A
benzene solution (1 L) of
Rf ϭ 0.86) and recovered starting material 24 (237 mg, 41%, Rf ϭ
0.57). Ϫ 25: Colorless plates (benzene/EtOH), m.p. 156.5Ϫ158.5
[3.3]MPCP-2,11-dione 11 (211 mg, 0.8 mmol) was irradiated as de-
scribed for 6. Progress of the reaction was monitored by TLC °C. Ϫ 1H NMR: δ ϭ 1.94Ϫ2.14 (m, 4 H, ϪCH2CH2CH2Ϫ),
(SiO2, CH2Cl2). After 5 h of irradiation, the solvent was removed 2.51Ϫ2.68 (m, 4 H, ϪCH2CH2CH2Ϫ), 2.77Ϫ2.92 (m, 4 H,
in vacuo, and the residue was purified using a short column of
ϪCH2CH2CH2Ϫ), 3.02 (s, 4 H, ϪCH2CH2Ϫ), 6.13 (s, 4 H, ArH),
silica gel with CH2Cl2 to give 12 (158 mg, 94%, Rf ϭ 0.83) as a 6.72 (s, 2 H, ArH). Ϫ EIMS: m/z ϭ 262 [Mϩ]. Ϫ C20H22 (262.4):
colorless solid. When the reaction was discontinued after irradi-
ation times of 30 min and 1 h, 12 (43%), [3.2]MPCP-2-one 13
(47%), and the starting material 11 (10%), and 12 (85%) and 13
(14%), respectively, were isolated. Separation was carried out by
silica gel preparative TLC (CH2Cl2) (Rf values of 12, 13, and 11
calcd. C 91.55, H 8.45; found C 91.49, H 8.41.
Acknowledgments
We gratefully acknowledge the financial support by a Grant-in-Aid
for Priority Area (A) of Creation of Delocalized Electronic Systems
(No. 12020241) from the Ministry of Education, Science, Sports
and Culture, Japan.
1
were 0.83, 0.50, and 0.25). Ϫ 12: H NMR: δ ϭ 2.10Ϫ2.22 (m, 2
H, ϪCH2CH2Ϫ), 2.47Ϫ2.58 (m, 2 H, ϪCH2CH2Ϫ), 2.72Ϫ2.80 (m,
2 H, ϪCH2CH2Ϫ), 3.11Ϫ3.18 (m, 2 H, ϪCH2CH2Ϫ), 5.41 (s, 1 H,
ArH), 5.85 (d, J ϭ 2.3 Hz, 2 H, ArH), 6.76 (m, 2 H, ArH), 6.95
(t, J ϭ 7.4 Hz, 1 H, ArH), 7.19 (d, J ϭ 2.0 Hz, 2 H, ArH) [ref.[20]
:
[1]
δ ϭ 1.87Ϫ3.12 (m, 8 H, ϪCH2CH2Ϫ), 5.24 (s, 1 H, ArH), 5.70 (d,
J ϭ 1.9 Hz, 2 H, ArH), 6.63 (m, 3 H, ArH), 6.97 (d, J ϭ 1.9 Hz,
2 H, ArH)].
H. Isaji, Ph.D. Dissertation, Kyushu University, 1999.
Part 5: K. Sako, H. Tatemitsu, S. Onaka, H. Takemura, S. Os-
[2]
ada, G. Wen, J. M. Rudzinski, T. Shinmyozu, Liebigs Ann.
1996, 1645Ϫ1649.
[3] [3a]
[3.2]Metaparacyclophane-2-one (13): A benzene solution (500 mL)
of 11 (405 mg, 1.53 mmol) was irradiated for 26 min as described
for 6. The solvent was removed in vacuo and the residue was puri-
fied by preparative silica gel TLC with CH2Cl2 to give 13 (167 mg,
46%, Rf ϭ 0.54) as a colorless solid, along with 12 (46 mg, 14%,
Rf ϭ 0.93) and recovered starting material 11 (89 mg, 22%, Rf ϭ
0.33). Ϫ 13: Colorless crystals (hexane), m.p. 121.0Ϫ122.5 °C. Ϫ
1H NMR: δ ϭ 2.7 (br s, 2 H, ϪCH2CH2Ϫ), 2.9 (br s, 2 H,
ϪCH2CH2Ϫ), 3.28 (s, 2 H, ϪCH2COCH2Ϫ), 3.62 (s, 2 H,
ϪCH2COCH2Ϫ), 5.38 (s, 1 H, ArH), 6.2Ϫ6.8 (m, 4 H, ArH), 6.79
(d, J ϭ 7.3 Hz, 1 H, ArH), 6.90 (d, J ϭ 7.9 Hz, 1 H, ArH), 7.01
Y. Sakamoto, T. Kumagai, K. Matohara, C. Lim, T. Shin-
[3b]
myozu, Tetrahedron Lett. 1999, 40, 919Ϫ922. Ϫ
K. Mato-
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Tetrahedron Lett. 1999, 40, 6781Ϫ6784.
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H. Isaji, K. Sako, H. Takemura, H. Tatemitsu, T. Shinmyozu,
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W. K. Robbins, R. H. East-
[6d]
(t, J ϭ 7.6 Hz, 1 H, ArH). Ϫ IR (KBr): ν ϭ 1698 (CO) cmϪ1. Ϫ
man, J. Am. Chem. Soc. 1970, 92, 6076Ϫ6077. Ϫ
Robbins, R. H. Eastman, J. Am. Chem. Soc. 1970, 92,
W. K .
˜
FABMS: m/z ϭ 237 [M ϩ H] ϩ. Ϫ C17H16O (236.3): calcd. C 86.40,
6077Ϫ6079.
H 6.82; found C 86.29, H 6.84.
[7]
M. Shibahara, T. Shinmyozu, manuscript in preparation.
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K. Kurosawa, M. Suenaga, T. Inazu, T. Yoshino, Tetrahed-
[2.2]Paracyclophane (15): A benzene solution (1 L) of [3.3]PCP-
2,11-dione 14 (194 mg, 0.73 mmol) was irradiated as described for
6. After 4 h of irradiation, the solvent was removed in vacuo and
the residue was purified using a short column of silica gel with
CH2Cl2 to give 15 (149 mg, 97%, Rf ϭ 0.92) as a white solid. Ϫ
[8b]
ron Lett. 1982, 23, 5335Ϫ5338. Ϫ
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[9]
1
15: H NMR: δ ϭ 3.08 (s, 8 H, ϪCH2CH2Ϫ), 6.48 (s, 8 H, ArH)
[ref.[58]: δ ϭ 3.04 (s, 8 H, ϪCH2CH2Ϫ), 6.30 (s, 8 H, ArH)].
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[10b]
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[3.2]Paracyclophane-2-one (16): A benzene solution (500 mL) of 14
(142 mg, 0.54 mmol) was irradiated for 20 min as described for 6.
The solvent was removed in vacuo, and the residue was purified by
preparative silica gel TLC with CH2Cl2 to give 16 (27 mg, 21%,
Rf ϭ 0.62) as a white solid, along with 15 (11 mg, 10%) and starting
material 14 (29 mg, 20%). Ϫ 16: 1H NMR: δ ϭ 2.98 (s, 4 H,
ϪCH2CH2Ϫ), 3.70 (s, 4 H, ϪCH2CCH2Ϫ), 6.45 (d, J ϭ 7.9 Hz, 4
H, ArH) [ref.[17b]: δ ϭ 2.96 (s, 4 H, ϪCH2CH2Ϫ), 3.68 (s, 4 H,
ϪCH2CCH2Ϫ), 6.4Ϫ6.7 (AAЈBBЈ, 8 H, ArH)].
[10c]
Staab, Angew. Chem. Int. Ed. Engl. 1973, 12, 776Ϫ777. Ϫ
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A benzene solution (500 mL) of
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45, 4496Ϫ4498.
[3.3.3]PCP-2,11,20-trione 20 (106 mg, 0.27 mmol) was irradiated
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S. H. Mashraqui, K. R. Nivalkar, Tetrahedron Lett. 1997, 38,
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1
CH2Cl2) to give 21 (33 mg, 39%, Rf ϭ 0.76) as a white solid. Ϫ H
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J. Breitenbach, F. Ott, F. Vögtle, Angew. Chem. Int. Ed.
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:
[17b]
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[3.3.3](1,3,5)CP-2-one 24 (580 mg, 2.00 mmol) was irradiated as de-
scribed for 6. After 46 h of irradiation, the reaction mixture was
concentrated to dryness, and the residue was separated by silica gel
column chromatography with toluene to give 25 (178 mg, 34%,
[18b]
Chem. Research (M) 1986, 2864Ϫ2872. Ϫ
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2498
Eur. J. Org. Chem. 2001, 2487Ϫ2499

[2.2]Cyclophanes and [3.2]Cyclophanes from [3.3]Cyclophane-2,11-diones
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