σ-Antiaromaticity in Cyclobutane, Cubane, and Other Molecules with Saturated Four-Membered Rings
2002; American Chemical Society; Volume: 5; Issue: 1 Linguagem: Inglês
10.1021/ol027159w
ISSN1523-7060
AutoresDamian Moran, Mariappan Manoharan, Thomas Heine, Paul von Ragué Schleyer,
Tópico(s)Chemical Reaction Mechanisms
ResumoDissected nucleus-independent chemical shift (NICS) analyses of cycloalkanes and cage hydrocarbons reveal contrasting ring current effects, diatropic in three- and five-membered and paratropic in four-membered ring systems. The large shielding effects of the C−C bonds of the archetypal σ-aromatic, cyclopropane, are magnified in tetrahedrane and related structures. The remarkable deshielding effect of the cyclobutane C−C(σ) bonds is general: cubane and cages with four-membered rings are strongly deshielding (i.e., σ-antiaromatic).
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