Shenoy Siddhartha R, Smith Deborah M, Woerpel K A
Department of Chemistry, University of California-Irvine, Irvine, CA 92697-2025, USA.
J Am Chem Soc. 2006 Jul 5;128(26):8671-7. doi: 10.1021/ja061110u.
The limitations of stereoelectronic models in assessing the stereoselective nucleophilic substitution reactions of cyclic oxocarbenium ions at high reaction rates are discussed. Evidence is provided suggesting that the diastereoselectivity of nucleophilic substitution reactions is attenuated at the limits of diffusion control. The low diastereoselectivities observed in the reactions of trimethylsilyl cyanide with five- and six-membered ring oxocarbenium ions are attributed to the high reactivity of the nucleophile and its reactions with these electrophiles at diffusion control rates.
讨论了立体电子模型在评估环状氧鎓离子在高反应速率下的立体选择性亲核取代反应时的局限性。提供的证据表明，亲核取代反应的非对映选择性在扩散控制的极限下会减弱。三甲基硅基氰化物与五元及六元环氧鎓离子反应中观察到的低非对映选择性归因于亲核试剂的高反应活性及其在扩散控制速率下与这些亲电试剂的反应。
