Full text of DOI:10.1016/S0040-4039(00)00599-2

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 41 (2000) 4177–4180
Novel silicon-bridged macrocycles: efficient synthesis by
quadruple cycloadditive macrocyclization and intramolecular
nitrile oxide dimerization
Chan Woo Lee, Gil Tae Hwang and Byeang Hyean Kim ∗
Department of Chemistry, Center for Biofunctional Molecules, Pohang University of Science and Technology,
Pohang 790-784, South Korea
Received 22 February 2000; revised 3 April 2000; accepted 7 April 2000
Abstract
Novel silacyclophanes have been synthesized by using quadruple cycloadditive macrocyclization and intramole-
cular nitrile oxide dimerization. The macrocyclic cycloadducts were characterized by spectroscopic methods and
X-ray crystallography. © 2000 Elsevier Science Ltd. All rights reserved.
Keywords: macrocycles; silicon heterocycles; cycloadditions; nitrile oxides.
Silicon-bridged macrocycles are of interest due to their additional coordination sites compared to
carbomacrocycles and good chemophysical properties including solubility. So far synthetic efforts
toward silacalixarenes,1 silacyclophanes,2 and a silacrown3 have been reported. We report here the
facile synthesis of novel silacyclophanes by using the quadruple cycloadditive macrocyclization (QCM)
methodology4 and intramolecular nitrile oxide dimerization,5 and their X-ray crystal structures. QCM
methodology based on 1,3-dipolar cycloaddition reaction provides a very efficient way to the silamacro-
cycles due to the short reaction sequences.
Silamacrocycle 3 was synthesized in a two-step sequence by using QCM methodology
(Scheme 1).4 Double cycloadditions between in situ-generated isophthaldinitrile oxide and 1,3-
divinyltetramethyldisiloxane provided [1+2] cycloadduct 2 as the major intermediate and further
cycloadditions between 2 and isophthaldinitrile oxide afforded the final [2+2] cycloadduct 36 as the
major product in 25% overall yield. The structure of silacyclophane 3 was identified by elemental
1
analysis, mass spectroscopy, IR, H NMR and 13C NMR, and confirmed by X-ray crystallography
(Fig. 1).7 The relative stereochemistry of the intermediate 2 was tentatively assigned by the X-ray
crystal structure of the final product 3. In a similar fashion, silacyclophanes 66 was prepared by QCM
methodology between terephthaldinitrile oxide and 1,3-divinyltetramethyldisiloxane (Scheme 1). Thus,
∗
Corresponding author. Tel: 82-562-279-2115; fax: 82-562-279-3399; e-mail: bhkim@postech.ac.kr (B. H. Kim)
0040-4039/00/$ - see front matter © 2000 Elsevier Science Ltd. All rights reserved.
PII: S0040-4039(00)00599-2
tetl 16878

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1,3-divinyltetramethyldisiloxane was served well as a bifunctional siladipolarophile with benzene-based
bifunctional dipoles.
Scheme 1.
Fig. 1. X-Ray crystal structure of 3
In the case of QCM with 2,6-pyridinedintrile oxide, two macrocyclic cycloadducts were isolated. The
first was the regular [2+2] cycloadduct 86 (8%) and the second was a [2+1] triple cycloadduct 96 (25%)
(Scheme 2). Silamacrocycle 8 is the pyridine version of compound 3 and was formed through QCM
in one pot. However, formation of compound 9 is rather unique and deserves attention. Very recently,
Mioskowski and co-workers5 reported the synthesis of medium- and large-size rings by intramolecular

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nitrile oxide dimerization, which results in the formation of furoxan moiety. During the dimerization
process, one of the nitrile oxides acts as a dipole whereas the other acts as a dipolarophile. Formation
of compound 9 proceeds via [2+1] double cycloadditions followed by intramolecular nitrile oxide
dimerization. Generation of the rather unusual product 9 may be attributable to the stability of 2,6-
pyridinedinitrile oxide and the proximity between two nitrile oxide moieties. The chemical structure
of 9 was confirmed by X-ray crystallography (Fig. 2).7
Scheme 2.
Fig. 2. X-Ray crystal structure of 9
In summary, we have synthesized novel silacyclophanes by using quadruple cycloadditive macrocycli-
zation and intramolecular nitrile oxide dimerization. With suitable siladipolarophiles these methodolo-
gies will provide an efficient route to various silamacrocycles.

4180
Acknowledgements
We are grateful to KOSEF (1999-2-123-001-3) for financial support and thank Professor Kimoon Kim
for X-ray crystallography.
References
1. König, B.; Rödel, M.; Bubenitschek, P.; Jones, P. G. Angew. Chem., Int. Ed. Engl. 1995, 34, 661–662.
2. (a) Kauffmann, T.; Kniese, H.-H. Tetrahedron Lett. 1973, 41, 4043–4046. (b) Birkofer, L.; Stuhl, O. J. Organomet. Chem.
1979, 177, C16–C18. (c) Kaes, C.; Hosseini, M. W.; Ruppert, R.; De Cian, A.; Fischer, J. Tetrahedron Lett. 1994, 35,
7233–7236. (d) Kaes, C.; Hosseini, M. W.; De Cian, A.; Fischer, J. J. Chem. Soc., Chem. Commun. 1997, 2229–2230.
3. Jung, M. E.; Xia, H. Tetrahedron Lett. 1988, 29, 297–300.
4. Kim, B. H.; Jeong, E. J.; Jung, W. H. J. Am. Chem. Soc. 1995, 117, 6390–6391.
5. Maugein, N.; Wagner, A.; Mioskowski, C. J. Org. Chem. 1999, 64, 8428–8431.
6. Selected spectroscopic data of 3, 6, 8 and 9. Compound 3: mp 267–270°C; 1H NMR (300 MHz, CDCl3) 7.77 (s, 2H, ArH),
7.60 (d, 4H, J=7.8 Hz, ArH), 7.34 (t, 2H, J=7.8 Hz, ArH), 3.98 (dd, 4H, J=15.7, 11.3 Hz, CH), 3.42–3.22 (m, 8H, CH2),
0.33 and 0.28 (2s, 24H, CH3); 13C NMR (75 MHz, CDCl3) 155.9, 130.8, 127.2, 127.0, 126.9, 74.3, 37.0, −1.6, −1.6,
−1.9, −2.0; FAB-MS (m/z) 693.3 (M++1); IR (CHCl3, cm−1) 2957, 1560, 1438, 1339, 1328, 1303, 1252, 1149, 1104,
903, 896, 883, 873, 841, 814, 789; anal. calcd for C32H44N4O6Si4: C, 55.46; H, 6.40; N, 8.08. Found: C, 55.60; H, 6.15;
1
N, 7.60. Compound 6: mp 261–263°C; H NMR (300 MHz, CDCl3) 7.59–7.32 (m, 8H, ArH), 4.08–3.97 (m, 4H, CH),
3.39–3.04 (m, 8H, CH2), 0.40–0.29 (m, 24H, CH3); 13C NMR (75 MHz, CDCl3) 156.6, 130.4, 126.7, 125.9, 74.4, 36.9,
−0.7, −1.0; FAB-MS (m/z) 693.3 (M++1); IR (CHCl3, cm−1) 2923, 2853, 1597, 1329, 1252, 1104, 874, 842, 789; anal.
calcd for C32H44N4O6Si4: C, 55.46; H, 6.40; N, 8.08. Found: C, 55.18; H, 6.22; N, 7.59. Compound 8: 1H NMR (300 MHz,
CDCl3) 8.00 (d, 2H, J=7.9 Hz, ArH), 7.76–7.67 (m, 4H, ArH), 4.12–3.98 (m, 4H, CH), 3.63–3.20 (m, 8H, CH2), 0.33–0.26
(m, 24H, CH3); 13C NMR (75 MHz, CDCl3) 158.0, 149.1, 136.7, 122.1, 74.8, 36.5, −0.8, −1.8, −2.1, −2.5; FAB-MS
(m/z) 695.2 (M++1); IR (CHCl3, cm−1) 2959, 2919, 2850, 1579, 1467, 1382, 1340, 1257, 1061, 924, 797; anal. calcd for
C30H42N6O6Si4·C2H5OH: C, 51.86; H, 6.53; N, 11.34. Found: C, 52.49; H, 6.29; N, 11.23. Compound 9: 1H NMR (300
MHz, CDCl3) 8.20–8.10 and 7.95–7.89 (2m, 6H, ArH), 4.29–4.15 (m, 2H; CH), 3.29–3.03 and 2.87–2.69 (2m, 4H, CH2),
0.30, 0.28, 0.10 and 0.07 (4s, 12H, CH3); 13C NMR (75 MHz, CDCl3) 157.4, 157.3, 150.2, 150.2, 147.2, 143.9, 137.6,
137.5, 123.9, 123.8, 123.0, 122.7, 77.1, 76.9, 35.8, 35.7, −1.4, −1.6; FAB-MS (m/z) 509.1 (M++1); IR (CHCl3, cm−1
)
2960, 1583, 1483, 1439, 1373, 1258, 1165, 1065, 992, 924; anal. calcd for C22H24N6O5Si2: C, 51.95; H, 4.76; N, 16.52.
Found: C, 51.60; H, 4.72; N, 16.25.
¯
7. Crystal data for 3: C32H44N4O6Si4, M=693.07, crystal system: triclinic, space group: P1, a=6.8037(8) Å, α=82.616(2)°,
b=9.3283(11) Å, β=77.729(2)°, c=15.4738(18) Å, γ=78.150(2)°, V=953.48(19) Å3, Z=1, dcalc=1.230 g cm−3, T=298(2)
K, Siemens SMART diffractometer with CCD detector, Mo-Kα (λ=0.71073Å), µ=2.04 cm−1, of 3728 measured data,
2750 were independent (Rint=0.0196), R1 [I >2σ(I)]=0.0574, wR2 (all data)=0.1297 and GOF=1.161. Crystal data for 9:
¯
C22H24N6O5Si2, M=508.65, crystal system: triclinic, space group: P1, a=8.6725(2) Å, α=75.9570(10)°, b=8.6733(2) Å,
β=86.1690(10)°, c=17.7650(2) Å, γ=71.1580(10)°, V=1226.77(4) Å3, Z=1, dcalc=0.689 g cm−3, T=193(2) K, Siemens
SMART diffractometer with CCD detector, Mo-Kα(λ=0.71073Å), µ=0.95 cm−1, of 5079 measured data, 3725 were
independent (Rint=0.0130), R1 [I >2σ(I)]=0.0388, wR2 (all data) =0.0997 and GOF=1.104.