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Straightforward Preparation and Stabilization of 2-trans-4 7 10 13-Diepoxy[15]annulenone.

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the most favorable structure for the unsubstituted N-methyleneformamide ; the s-cis-conformer is 0.1 1 kcal/mol,
the s-trans conformer 2.90 kcal/mol higher in energy.
Both according to experiment as well as to calculation,
the protonation of formamide takes place preferentially at
the oxygen atom. N-methylenecarboxamides, on the other
hand, are predicted by the calculations to be attacked at
the nitrogen atom. Oxygen protonation is less favorable by
7.00 kcal/mol. 1-Hydroxy-2-azaallyl cations are much
higher in energy (19.6 kcal/mol for the endo-isomer) than
the linear allenium ions.
Calculations on the structure of the 1-hydroxy-2-azaallenium ion reveal its unusual dynamic properties. An energy
of only 4 kcal/mol is necessary to convert the linear allenelike form into a 150"-bent structure; the methylene groups
remain twisted during this motion. Favorable compromises
in the overlap between the n-electron systems and the lone
pairs on nitrogen and oxygen are responsible for the unusual molecular flexibility predicted for these ions by the
Received: October 28, 1983 [Z 190 IE]
revised: December 20, 1982
German version: Angew. Chem. 95 (1983) 247
The complete manuscript of this communication appears in:
Angew. Chem. Suppl. 1983, 264-270
[4] M. C. Lasne, J.-L. Ripoll, A. Thuillier, J . Chem. Rex (S) 1982, 214.
[S] N-Acyl(methylene)ammonium salts as amidoalkylation reagents: e. g. H.
E. Zaugg, Synthesis 1970, 49; as isolated salt: e.g. T. Cohen, J. Lipowitz,
J. Am. Chem. SOC.86 (1964) 2514.
[7] E.-U. Wiirthwein, Angew. Chem. 93 (1981) 110; Angew. Chem. Int. Ed. 20
(1981) 99, and unpublished results.
[8] Evidence of N-protonation from 'H-'H-NMR coupling constants: G. R.
Krow, C. Pyun, C. Leitz, J. Marakowski, J . Org. Chem. 39 (1974) 2449.
[91 J. S . Binkley, J. A. Pople, W. J. Hehre, J . Am. Chem. S0.c 102 (1980)
Straightforward Preparation and Stabilization of
2-rruns-4,7 :10,13-DiepoxyIl5lannulenone
Scheme 1. The [15]annulenone-hydroxy[lS]annulenylium ion cycle.
(3:2 = 12 : 1). Addition of saturated NaHCO, solution to
3, which could be regenerated at 25" C in CF3COOD, followed by chromatographic separation (CHzCl2, A1203,activity 111) gave pure 4. 4 proved to be diatropic; the outer
protons absorb in the region 6=6.82-8.18 (9H) and the
inner proton at 6=4.54 (JImnS
= 16 Hz, in CDCI3, 27 "C).
The chemical shift of the inner proton is highly temperature- and solvent-dependent. In D,COD progressive highfield shifts occur on cooling [S=2.51 (0 "C), 1.85 (-25 "C),
and 0.57 (- 55 "C)]. Such large shifts were also observed at
25 "C on increasing the D,O content [6=3.02 (D3COD:
D20= 100 :O), 2.60 (100: 16), 1.31 (100 :40), 0.87 (100 :56)].
These observations indicate that the dipolar stretched form
5 is formed by H-bonding to stabilize the trans geometry.
Kinetic measurements of the isomerization 4-1 (UV
spectroscopy) confirmed these results. As expected, the
rates of isomerization, which could be best approximated
by eq. (I), became slower in aqueous solvents indicating
that kH*in CH30H is ca. 3 times greater than kHf in 25%
aqueous CH,OH, and that kH+(in acetone)/k,+ (in 25%
aqueous MeOH) is at least several thousand.
By Ham Ogawa*, Tadashi Inoue, Taiji Imoto,
Izumi Miyamoto, Hidefumi Kato, and Yoichi Taniguchi
Although the 2-trans-[l5]annulenone 4 with two oxygen
bridges has been prepared"', its fugitive existence has precluded further studies. We now report a [15]annulenone-hydroxy[ 15]annulenylium ion cycle, from which 4
could be isolated as predominant isomer. It was also
found that the ground state of 4 could be stabilized by
HZOto form a 14n-annulenylioolate 5 , R = H (Scheme 1).
The cis-annulenylium ion 2 was formed by dissolving 1
in CF3COOD+CD2Cl, (1 : 5 ) at -60 "C ['H-NMR: AB
system centered at 6=8.61 and 8.99 (Jcis
=9.77 Hz), 4H, H2, H-3, H-14, and H-15; singlet at 6=9.06, 6H, H-5, H-6,
H-8, H-9, H-11, and H-121.
On warming the solution the 'H-NMR spectrum
changed dramatically to give nine outer proton resonances
(S= 8.85- 10.30) and one inner proton resonance
(S = - 3.68, Jtrans= 14.6 Hz), indicating that the cis-trans
equilibrium 2 + 3 shifts considerably towards 3
[*] Prof. Dr. H. Ogawa, T. Inoue, Prof. Dr. T. Imoto
Faculty of Pharmaceutical Sciences, Kyushu University 62
Maidashi, Fukuoka 812 (Japan)
I. Miyamoto, Dr. H. Kato, Prof. Dr. Y.Taniguchi
Department of General Chemistry, National Kurume Technical College
Komorino, Kurume 830 (Japan)
Angew. Chem. Int. Ed. Engl. 22 (1983) No. 3
A significant feature of the annulenone cycle is the fact
that a series of cooperative conformational changes could
occur in succession to drive it by a protonation-deprotonation sequence. Interestingly, similar transformations occur
in bacteriorhodopsinI6l. Thus, the cycle could provide the
first example of a "closed" cyclelsJ,whose rates and equilibria can be investigated as a model of a biological cycle using conventional kinetics and thermodynamic^[^^.
Received: May 27, 1981 [Z 415 IE]
revised: January 10, 1983
German version: Angew. Chem. 95 (1983) 244
The complete version of this communication appears in:
Angew. Chem. Suppl. 1983, 243-253
CAS Registry numbers:
1, 36216-07-6; 2, 74651-55-1; 3, 74651-57-3; 4, 36216-08-7.
[l] H. Ogawa, N. Shimojo, H. Kato, H. Saikachi, Tetrahedron 30 (1974)
[5I T. L. Hill: Free Energy Transduction in Biology, Academic Press, New
York 1977, p. 213.
161 D. Oesterhelt, Angew. Chem. 88 (1976) 16; Angew. Chem. Int. Ed. Engl. 15
(1976) 17; W. Stoekenius, R. H. Rozier, R. A. Bogomolni, Biochim. Biophys. Acta 505 (1978) 215.
0 Verlag Chemie GmbH, 6940 Weinheim, 1983
0570-0833/83/0303-0253 $02.50/0
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preparation, diepoxy, annuleno, straightforward, transp, stabilization
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