Synthesis and complexation properties of a synthetic receptor, Z-tetrabenzohexadehydro[16]annulene

Article abstract of DOI:10.1016/S0040-4039(01)01399-5

Z-Tetrabenzohexadehydro[16]annulene (1), a synthetic receptor, easily produces its silver(I) complexes both in solution and in the solid state. The X-ray analysis of the silver(I) complexes of 1 revealed unique structures of the dinuclear complexes.

Full text of DOI:10.1016/S0040-4039(01)01399-5

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 42 (2001) 6883–6886
Synthesis and complexation properties of a synthetic receptor,
Z-tetrabenzohexadehydro[16]annulene†
Masahiko Iyoda,* Takeru Horino, Futoshi Takahashi, Masashi Hasegawa, Masato Yoshida and
Yoshiyuki Kuwatani
Department of Chemistry, Graduate School of Science, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397, Japan
Received 21 June 2001; accepted 27 July 2001
Abstract—Z-Tetrabenzohexadehydro[16]annulene (1), a synthetic receptor, easily produces its silver(I) complexes both in solution
and in the solid state. The X-ray analysis of the silver(I) complexes of 1 revealed unique structures of the dinuclear complexes.
© 2001 Elsevier Science Ltd. All rights reserved.
Synthetic receptors have received considerable attention
in recent years1 because of their unique structures2 and
host/guest interactions,3 and as a potential device for
switches.4 Z-Tetrabenzohexadehydro[16]annulene (1)
possesses a concave p-system which could play a role in
complexation for transition metal cations, as shown in
Fig. 1. We now report the synthesis of 1 and its
complex formation with a silver cation in solution and
in the solid state.
silver(I) complexes.5 Although 2 bears a stacked struc-
ture both in solution and in the solid state,5a the
structures of its silver(I) complexes are flexible depend-
ing on the coordination conditions and crystal pack-
ing.5b The mobile structural change in 2 reflects the
existence of four Z-double bonds. In contrast, Z-tetra-
benzohexadehydro[16]annulene (1) exists as an equi-
librium mixture of two conformers, and the spoon-like
space in 2 can scoop up a metal cation effectively (Fig.
1).6 The short radius of the elliptic inner space is ca. 5
,
Recently, we reported the synthesis of all-Z-tetra-
benzo[16]annulene (2) and the X-ray structure of the
A, and hence the silver cation can be captured inside
effectively like 1·M+, as shown in Fig. 1.
Figure 1. The conformations of 1, 2, and their complexes with M+.
Keywords: annulenes; complexes; macrocycles; receptors; silver and compounds; X-ray crystal structures.
* Corresponding author. Tel.: +81-426-77-2547; fax: +81-426-77-2525; e-mail: iyoda-masahiko@c.metro-u.ac.jp
† This paper is dedicated to Emeritus Professor Masazumi Nakagawa on the occasion of his 85th birthday.
0040-4039/01/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved.
PII: S0040-4039(01)01399-5

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M. Iyoda et al. / Tetrahedron Letters 42 (2001) 6883–6886
temperatures. Although the 1H NMR spectrum of 1
was unchanged by adding CuOTf, the addition of
silver(I) salts (excess) caused a marked low-field shift of
the olefinic and aromatic proton signals. These results
indicate that 1 forms stable complexes with many sil-
ver(I) salts. Thus, a solution of 1 and a silver salt
(1.4–2.0 eqiuv.) in THF was stirred for 30 min at room
temperature, followed by removal of the solvent to
afford a crude salt. A pure silver salt was obtained in
moderate to good yields by recrystallization from hex-
ane–CH2Cl2 or benzene–CH2Cl2, as shown in Table 1.
In CDCl3 solutions of the silver salts, signals of the
olefinic and aromatic protons shift markedly to low-
field as compared to those of 1 [1: l 7.01 (s, olefinic),
7.12–7.61 (m, Ar A), and 7.12–7.31 (m, Ar B)]. On the
basis of the Job plot’s experiments, a 1:1 complex
The synthesis of 1 was carried out according to the
reaction sequence outlined in Scheme 1. The Sono-
gashira coupling of bis(2-bromophenyl)ethyne 37 with 4
(2.52 equiv.) in refluxing Et3N for 2 h afforded the
triyne 5 (84%).8 Removal of the t-butyldimethylsilyl
(TBDMS) group in 5 (80%), followed by Dess–Martin
oxidation (91%) yielded the dialdehyde 6. The
intramolecular pinacol coupling of 6 with a low-valent
vanadium complex9 generated from VCl3(THF)3 and
Zn in CH2Cl2–DMF at room temperature produced
selectively the erythro-7 (84%) together with a small
amount of the threo-isomer (5.5%). The reaction of
erythro-7 with 1,1%-thiocarbonyldiimidazole (TCDI) in
refluxing toluene for 16 h afforded the thionocarbonate
8 (92%), which, on treatment with 1,3-dimethyl-2-
phenyl-1,3,2-diazaphospholidine (DMPD)10 in refluxing
benzene for 14 h, produced the desired 1 in 68% yield.
formed
in
solution
when
1·(AgClO4)2
and
1·(AgOCOCF3)2 were dissolved in CDCl3. The VT
1
The MOPAC PM3 calculations indicate that 1 has a
NMR experiments indicated that the H NMR spectra
1
twisted structure, as shown in Fig. 1. Since the H and
of 1·(AgClO4)2 and 1·(AgOCOCF3)2 broadened at
−60°C, and very broad spectra were observed at −90°C,
due to the conformational change even at low tempera-
13C NMR spectral data of 1 at −90°C show a Cs
structure, rapid interconversion takes place even at low
Scheme 1. Synthesis of 1. (a) Pd(PPh3)4, CuI, Et3N; (b) HF, CH3CN, rt; (c) Dess–Martin reagent (2.25 equiv.), CH2Cl2, rt; (d)
VCl3(thf)3, Zn, CH2Cl2, DMF, rt; (e) thiocarbonyldiimidazole (TCDI), toluene, reflux; (f) 1,3-dimethyl-2-phenyl-1,3,2-diazaphos-
pholidine (DMPD), benzene, reflux.
1
Table 1. Preparation and H NMR data of silver complexes derived from 1a
Ag salt
Yield
Ratiob
1H NMR (l in CDCl3)c
AgOTf
AgClO4
AgBF4
AgSbF6
AgOCOCF3
AgNO3
66
81
81
81
60
42
1:1
1:2
1:1
1:1
1:2
1:1
7.55 (s, olefin); 7.13–7.76 (m, Ar A); 7.28–7.46 (m, Ar B)
7.77 (s, olefin); 7.22–7.81 (m, Ar A); 7.32–7.50 (m, Ar B)
7.79 (s, olefin); 7.26–7.82 (m, Ar A); 7.31–7.52 (m, Ar B)
7.77 (s, olefin); 7.32–7.86 (m, Ar A); 7.37–7.55 (m, Ar B)
7.55 (s, olefin); 7.13–7.76 (m, Ar A); 7.28–7.46 (m, Ar B)
7.40 (s, olefin); 7.13–7.63 (m, Ar A); 7.25–7.43 (m, Ar B)
a The complexes were prepared in THF, and recrystallized from n-C6H14–CH2Cl2 or C6H6–CH2Cl2.
b The ratio of 1 and Ag salt was determined by elemental analysis.
c The 1H NMR spectra of crystalline silver salts were measured in CDCl3 at room temperature.

M. Iyoda et al. / Tetrahedron Letters 42 (2001) 6883–6886
6885
Figure 2. ORTEP diagram of 1·(AgClO4)2. (a) Molecular structure of 1. Perchlorate ions are omitted for clarity. Selected bond
,
lengths [A] and angles [°]: Ag1ꢀC4 2.63(1), Ag1ꢀC5 2.55(1), Ag1ꢀC8 2.500(9), Ag2ꢀC9 2.507(9), C1ꢀC1* 1.29(2), C1ꢀC2 1.51(1),
C2ꢀC3 1.38(1), C3ꢀC4 1.43(1), C4ꢀC5 1.21(1), C6ꢀC7 1.39(2), C7ꢀC8 1.43(2), C8ꢀC8* 1.17(2), C3ꢀC4ꢀC5 174(1), C4ꢀC5ꢀC6
,
168(1), C7ꢀC8ꢀC8* 170.9(5). (b) Packing diagram. The dashed lines correspond to the AgꢀO bonds: (i) Ag1ꢀO4 2.94(1) A; (ii)
Ag1ꢀO5 2.75(1); (iii) Ag2ꢀO6 2.77(3); (iv) Ag2ꢀO1 2.74(2).
tures. The chemical shifts of the olefinic and aromatic
protons in the silver complexes reflect an effect of the
silver cation, and the complexation of AgClO4 and
AgBF4 with 1 is stronger than that of AgNO3, AgOTf,
and AgOCOCF3.
The crystal structures of the dinuclear complexes
1·(AgClO4)2 and 1·(AgOCOCF3)2 were determined by
X-ray analysis (Figs. 2 and 3).11 As shown in Fig. 2(a),
the molecular structure of 1·(AgClO4)2 has a crystallo-
graphic Cs symmetry with a mirror plane passing
through the mid-point of the C(1)ꢀC(1*) and
C(8)ꢀC(8*) bonds. The [16]annulene ring has a dipper-
like structure, and the Ag(1) atom is located in the
center of the annulene ring and is connected to three
acetylenic bonds, whereas the Ag(2) atom binds to the
C9 and C9* carbons. The C(3)ꢀC(8) and C(3*)ꢀC(8*)
carbons are located on the plane, and the maximum
,
atomic deviation from the least-squares plane is 0.04 A.
In contrast, the length of the olefinic bond C(1)ꢀC(1*)
,
is 1.34(2) A, reflecting a coordination-free double bond
character. The crystal packing contains a stacked
diphenylacetylene unit, and the face-to-face distance is
,
3.9 A (Fig. 2(b)). The annulene–AgClO4 and the sty-
rene–AgClO4 moieties also stack together with the
AgꢀO bonds (the dotted lines i–iv in Fig. 2(b)) along
with the diphenylacetylene column, and the distance of
,
Ag(1)ꢀAg(1) and Ag(2)ꢀAg(2) is 7.90 A.
Figure 3. Packing diagram of 1·(AgOCOCF3)2. Selected bond
As shown in Fig. 3, 1·(AgOCOCF3)2 has an interesting
packing structure. The [16]annulene ring has a twisted
structure like 1·M+ in Fig. 1, and the Ag(1) atom binds
to the two acetylenic bonds, presumably due to the
weak cationic character of the Ag ion in AgOCOCF3.12
,
lengths [A] and angles [°]: Ag1ꢀC1 2.500(6), Ag1ꢀC2 2.443(5),
Ag1ꢀC5 2.555(5), Ag1ꢀC6 2.742(5), Ag1ꢀC13 2.827(6),
Ag1ꢀC14 2.801(6), Ag1ꢀO1 2.222(4), Ag2ꢀO2 2.376(4),
Ag2ꢀO3 2.256(4), Ag2ꢀO4 2.242(4), C1ꢀC2 1.202(8), C2ꢀC3
1.424(8), C3ꢀC4 1.415(7), C4ꢀC5 1.429(7), C5ꢀC6 1.209(7),
C9ꢀC10 1.193(8), C13ꢀC14 1.326(9), C1ꢀC2ꢀC3 167.6(6),
C2ꢀC1ꢀC16 170.0(6), C4ꢀC5ꢀC6 166.8(6), C5ꢀC6ꢀC7
172.6(6), C8ꢀC9ꢀC10 175.7(6), C9ꢀC10ꢀC11 178.0(7).
,
The distances (2.44–2.74 A) of the Ag(1)ꢀacetylene
bonds in 1·(AgOCOCF3)2 are similar to those (2.50–
,
2.63 A) of the Ag(1)ꢀacetylene bonds in 1·(AgClO4)2.
The distances of Ag(1)ꢀC(13) and Ag(1)ꢀC(14) are

6886
M. Iyoda et al. / Tetrahedron Letters 42 (2001) 6883–6886
,
2.80–2.83 A, reflecting a weak interaction between the
Ag(1) ion and the olefinic bond. Interestingly, a planar
eight-membered ring containing the two Ag(2) atoms is
formed between the annuleneꢀAg(1) complexes, the
maximum atomic deviation from the least-squares
7. (a) Letsinger, R. L.; Nazy, J. R. J. Am. Chem. Soc. 1959,
81, 3013; (b) Diercks, R.; Vollhardt, K. P. C. Angew.
Chem., Int. Ed. Engl. 1986, 25, 266.
8. All compounds gave satisfactory analytical and spectral
data. For example, 6: colorless needles, mp 158.2–
159.6°C, MS m/z 434 (M+); 1H NMR (CDCl3) l 7.33–
7.36 (m, 2H, Ar) 7.38–7.44 (m, 10H, Ar), 7.60–7.66 (m,
4H, Ar), 7.80–7.82 (m, 2H, Ar), 10.60 (s, 2H, CHO); 13C
NMR (CDCl3) l 89.1, 92.3, 95.1, 124.9, 125.5, 126.67,
126.72, 128.56, 128.61, 128.9, 132.2, 132.3, 133.28, 133.33,
135.8, 191.5; IR (KBr) 2214, 1691 cm−1. Erythro-7: color-
,
plane being 0.04 A. All silver atoms in 1·(AgOCOCF3)2
are connected with the acetate (OꢀCꢀO) bridges to
form a triple-decker structure.
Acknowledgements
1
less leaflets, mp 239°C (decomp), MS m/z 436 (M+); H
NMR (CDCl3) l 2.71 (br. s, 2H, OH), 5.76 (d, J=1.8 Hz,
2H, CH), 7.17 (m, 2H, Ar), 7.22 (m, 2H, Ar), 7.31 (m,
2H, Ar), 7.33 (m, 2H, Ar), 7.35 (m, 2H, Ar), 7.37 (dd,
J=7.8, 1.1, 2H, Ar), 7.50–7.52 (m, 2H, Ar), 7.59–7.61 (m,
2H, Ar); 13C NMR (CDCl3) l 74.0, 91.4, 92.1, 92.6,
122.0, 125.1, 125.4, 127.3, 127.4, 128.0, 128.1, 128.2,
Financial support for this study was provided by
Grants-in-Aid for Scientific Research on Priority Areas
from the Ministry of Education, Culture, Sports, Sci-
ence and Technology, Japan (10440190). We also thank
Professor Haruo Matsuyama, Muroran Institute of
Technology, and Mr. Masanori Ohkoshi, Tokyo
Metropolitan University, for helpful discussions.
132.47, 132.50, 132.54, 140.4; IR (KBr) 3422, 2213 cm−1
.
8: colorless leaflets, mp 215°C (decomp), FAB-MS m/z
479 (M++1); 1H NMR (CDCl3) l 5.30 (s, 2H, CH),
7.15–7.26 (m, 6H, Ar), 7.33–7.42 (m, 6H, Ar), 7.55 (dd,
J=7.7, 1.3, 2H, Ar), 7.65 (dd, J=7.6, 1.2, 2H, Ar); 13C
NMR (CDCl3) l 84.2, 89.9, 92.3, 93.6, 122.3, 124.2,
124.7, 126.9, 128.2, 128.4, 128.7, 129.2, 132.4, 133.09,
133.11, 133.4, 192.0. 1: colorless plates, mp 202°C
(decomp), MS m/z 402 (M+); 1H NMR (CDCl3) l 7.01 (s,
2H, CHꢁ), 7.12–7.18 (m, 6H, Ar), 7.27–7.31 (m, 4H, Ar),
7.46–7.49 (m, 2H, Ar), 7.50–7.54 (m, 2H, Ar), 7.58–7.61
(m, 2H, Ar); 13C NMR (CDCl3) l 92.56, 92.63, 93.3,
122.5, 125.1, 125.2, 126.8, 127.8, 127.9, 128.0, 128.8,
130.2, 132.8, 132.9, 133.4, 139.3; UV (solv.) umax (o) 284
(127,000), 324 (36,400) nm.
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11. Crystal data for 1·(AgClO4)2 and 1·(AgOCOCF3)2.
1·(AgClO4)2: C32H18O8Cl2Ag2, Mw=817.13, monoclinic,
space group C2/m (No. 12), a=25.133(3), b=14.724(3),
3
,
,
4. For a review, see: Comprehensive Supramolecular Chem-
istry; Reinhoudt, D. N., Ed. Supramolecular technology.
Elsevier Science, 1996; Vol. 10.
c=7.902(2) A, i=98.65(2)°, V=2891(1) A , Z=4, Dc=
1.877 g cm−3, R1=0.070, Rw=0.208, GOF=1.09 for 1858
reflections
with
I>3.00|(I).
1·(AgOCOCF3)2:
5. (a) Kuwatani, Y.; Yoshida, T.; Kusaka, A.; Iyoda, M.
Tetrahedron Lett. 2000, 41, 359; (b) Kuwatani, Y.;
Yoshida, T.; Hara, K.; Yoshida, M.; Matsuyama, H.;
Iyoda, M. Org. Lett. 2000, 2, 4017.
6. For the silver complexes of octadehydro[16]annulene, see:
Nishinaga, T.; Kawamura, T.; Komatsu, K. J. Chem.
Soc., Chem. Commun. 1998, 2263.
C36H18O4F6Ag2, Mw=844.26, monoclinic, space group
P21/n (No. 14), a=16.564(3), b=8.924(3), c=22.813(3)
3
,
,
A, i=107.67(1)°, V=3213(1) A , Z=4, Dc=1.745 g
cm−3, R1=0.042, Rw=0.068, GOF=1.35 for 4431 reflec-
tions with I>3.00|(I).
12. Attempts to determine the X-ray structures of 1·AgOTf
and 1·AgBF4 were unsuccessful until now.