Conformational properties of simple monocyclic conjugated enediynes

Yavari, Issa; Dadgar, Mohsen

doi:10.1016/s0166-1280(97)00097-3

Cited by 4 publications

(2 citation statements)

References 16 publications

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“…Yavari et al . reported on some of these structures using semi‐empirical AM1 calculations, but the crystal structure showed the C 1 symmetric conformation 2A …”

Section: Resultsmentioning

confidence: 99%

“…Theoretical studies on 2 tended to focus on either one or two conformers . The 9‐membered ring (3 Z )‐3‐cyclononene‐1,5‐diyne ( 3 ) (Scheme B) was found to adopt a C S symmetric conformation . The 10‐membered ring (3 Z )‐3‐cyclodocene‐1,5‐diyne ( 4 ) (Scheme B) exists in two conformations of C 2 and C 1 symmetry, and the C 2 conformer reaction surface of 4 has been examined theoretically …”

Section: Introductionmentioning

confidence: 99%

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A Curtin–Hammett pentamethylene chain symmetrization process in the Bergman cyclization of an 11‐membered ring enediyne

Greer

Lavinda

2012

J of Physical Organic Chem

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Pentamethylene chain conformational effects for the Bergman cyclization of the 11-membered ring enediyne, (3Z)-3cycloundecene-1,5-diyne, 2, are examined theoretically with unrestricted Becke, three-parameter, Lee-Yang-Parr/6-31 G(d,p) calculations. A C 1 symmetric enediyne conformation was found to be the global minimum, where its nonsymmetric pentamethylene chain prevented p-orbital alignment of the acetylene groups for C-C s bond product formation. The Bergman cyclization of 2 was found to be conformationally dependent. In a Curtin-Hammett type process, the C 1 symmetric 2 inverts to one of the C S or C 2 symmetric conformers required for the Bergman cyclization, which produced a C S or C 2 symmetric 1,4-diradical intermediate. The activation energy for the cyclization is slightly higher to reach the C 2 symmetry diradical compared with the C S symmetry diradical. a Enthalpies at 298 K: ΔH 298 = Δ(E 0 + H corr ), E 0 = the total electronic energy, H corr = E tot + k b T, E tot = internal thermal energy, k b = Boltzmann constant. b Energies at 298 K: Δ(E 0 + ZPE).

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“…Yavari et al . reported on some of these structures using semi‐empirical AM1 calculations, but the crystal structure showed the C 1 symmetric conformation 2A …”

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%