Abstract
Conformational behavior of 2,2,11,11-tetradeuterio[3.3]metacyclophanes 1-d4 and 2-d4 has been studied by a variable-temperature (VT) 1H NMR method. In order to simplify the interpretation of the NMR spectrum, four deuteriums were introduced at C-2 and C-11 positions of the trimethylene bridges of [3.3]metacyclophanes by reductive desulfurization of 2,11-bis(1,4-dithiabutane-1,4-diyl)[3.3]metacyclophanes 4 and 5 with tri-n-butyltin deuteride. Our previous conformational study of tetradeuterio-1,4-dioxa[4.3.3]cyclophane (3-d4) revealed that the temperature-dependent phenomenon in the NMR spectrum of 1 was ascribed to the inversion the trimethylene bridges. The work also suggested the presence of benzene ring inversion. To confirm this, optically active [3.3]metacyclophanechromium tricarbonyl complexes (-)- and (±)-17 were prepared by means of the HPLC separation of racemic complex (±)-17 using a chiral stationary phase. Racemization occurred when (-)- and (+)-17 were decomplexed at 20 °C. This result as well as the fact that the energy barrier (ΔG*) for the benzene ring inversion could not be detected by the VT NMR method indicated that the barrier is much lower than that of trimethylene bridge inversion (ΔG* = 11-12 keal/mol). The most stable conformer of 1-d4 and 2-d4 is a syn-(chair-chair), and the less stable conformer is estimated to be a syn(chair-boat) on the basis of the 1H NMR data.
| Original language | English |
|---|---|
| Pages (from-to) | 6536-6541 |
| Number of pages | 6 |
| Journal | Journal of Organic Chemistry |
| Volume | 57 |
| Issue number | 24 |
| DOIs | |
| Publication status | Published - Nov 1 1992 |
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All Science Journal Classification (ASJC) codes
- Organic Chemistry
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A Conformational Study of [3.3]Metacyclophanes through Variable-Temperature 1H NMR and Optical Rotation. / Sako, Katsuya; Shinmyozu, Teruo; Takemura, Hiroyuki; Suenaga, Masahiko; Inazu, Takahiko.
In: Journal of Organic Chemistry, Vol. 57, No. 24, 01.11.1992, p. 6536-6541.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - A Conformational Study of [3.3]Metacyclophanes through Variable-Temperature 1H NMR and Optical Rotation
AU - Sako, Katsuya
AU - Shinmyozu, Teruo
AU - Takemura, Hiroyuki
AU - Suenaga, Masahiko
AU - Inazu, Takahiko
PY - 1992/11/1
Y1 - 1992/11/1
N2 - Conformational behavior of 2,2,11,11-tetradeuterio[3.3]metacyclophanes 1-d4 and 2-d4 has been studied by a variable-temperature (VT) 1H NMR method. In order to simplify the interpretation of the NMR spectrum, four deuteriums were introduced at C-2 and C-11 positions of the trimethylene bridges of [3.3]metacyclophanes by reductive desulfurization of 2,11-bis(1,4-dithiabutane-1,4-diyl)[3.3]metacyclophanes 4 and 5 with tri-n-butyltin deuteride. Our previous conformational study of tetradeuterio-1,4-dioxa[4.3.3]cyclophane (3-d4) revealed that the temperature-dependent phenomenon in the NMR spectrum of 1 was ascribed to the inversion the trimethylene bridges. The work also suggested the presence of benzene ring inversion. To confirm this, optically active [3.3]metacyclophanechromium tricarbonyl complexes (-)- and (±)-17 were prepared by means of the HPLC separation of racemic complex (±)-17 using a chiral stationary phase. Racemization occurred when (-)- and (+)-17 were decomplexed at 20 °C. This result as well as the fact that the energy barrier (ΔG*) for the benzene ring inversion could not be detected by the VT NMR method indicated that the barrier is much lower than that of trimethylene bridge inversion (ΔG* = 11-12 keal/mol). The most stable conformer of 1-d4 and 2-d4 is a syn-(chair-chair), and the less stable conformer is estimated to be a syn(chair-boat) on the basis of the 1H NMR data.
AB - Conformational behavior of 2,2,11,11-tetradeuterio[3.3]metacyclophanes 1-d4 and 2-d4 has been studied by a variable-temperature (VT) 1H NMR method. In order to simplify the interpretation of the NMR spectrum, four deuteriums were introduced at C-2 and C-11 positions of the trimethylene bridges of [3.3]metacyclophanes by reductive desulfurization of 2,11-bis(1,4-dithiabutane-1,4-diyl)[3.3]metacyclophanes 4 and 5 with tri-n-butyltin deuteride. Our previous conformational study of tetradeuterio-1,4-dioxa[4.3.3]cyclophane (3-d4) revealed that the temperature-dependent phenomenon in the NMR spectrum of 1 was ascribed to the inversion the trimethylene bridges. The work also suggested the presence of benzene ring inversion. To confirm this, optically active [3.3]metacyclophanechromium tricarbonyl complexes (-)- and (±)-17 were prepared by means of the HPLC separation of racemic complex (±)-17 using a chiral stationary phase. Racemization occurred when (-)- and (+)-17 were decomplexed at 20 °C. This result as well as the fact that the energy barrier (ΔG*) for the benzene ring inversion could not be detected by the VT NMR method indicated that the barrier is much lower than that of trimethylene bridge inversion (ΔG* = 11-12 keal/mol). The most stable conformer of 1-d4 and 2-d4 is a syn-(chair-chair), and the less stable conformer is estimated to be a syn(chair-boat) on the basis of the 1H NMR data.
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U2 - 10.1021/jo00050a031
DO - 10.1021/jo00050a031
M3 - Article
AN - SCOPUS:0000426203
VL - 57
SP - 6536
EP - 6541
JO - Journal of Organic Chemistry
JF - Journal of Organic Chemistry
SN - 0022-3263
IS - 24
ER -