Baghdasarian Glen, Woerpel K A
Department of Chemistry, University of California-Irvine, Irvine, CA 92697-2025, USA.
J Org Chem. 2006 Sep 1;71(18):6851-8. doi: 10.1021/jo060968z.
Nucleophilic substitution reactions of 4-substituted cyclohexanone acetals display different selectivities depending upon the electronic nature of the substituent. Alkyl groups favor equatorial positions in the oxocarbenium ions, but alkoxy groups prefer axial conformers. The reactions of acetals with alkoxy groups constrained to either equatorial or axial positions suggest that the presence of an axial alkoxy group distorts the oxocarbenium ion, changing its inherent preferences for facial attack.
4-取代环己酮缩醛的亲核取代反应根据取代基的电子性质表现出不同的选择性。烷基在氧鎓离子中有利于占据平伏键位置，但烷氧基则更倾向于直立构象体。缩醛与被限制在平伏键或直立键位置的烷氧基的反应表明，直立烷氧基的存在会扭曲氧鎓离子，改变其对面进攻的固有偏好。
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