In this computational study, density functional theory (DFT) calculations at the M06/6-311G(d,p) level of theory were employed to study the regio-, stereo-, and site-selectivities of 1,3-dipolar cycloadditions of benzonitrile oxide (BNO) with unsymmetrically substituted norbornenes and norbornadienes. The reactions between BNO and unsymmetrically-substituted 2-norbornes and unsymmetrically-substituted 2-norbornadienes proceed with the oxygen of the BNO attacking the more hindered side of the double bond in all cases except when strong EWGs are introduced. For the reaction between BNO and unsymmetrically-substituted 2-norbornadienes, varying degrees of selectivities are observed depending on the substituent, indicating that site-selectivity is largely influenced by nature of substituents. Generally, the regio-isomers in which the oxygen of the BNO is bonded to the more hindered side of the double bond are favored except when strong EWGs are introduced, and exo stereo-isomers are generally favored over the endo stereo-isomers. Electrophilic (P_k⁺) and nucleophilic (P_k^-) Parr functions computations are in complete agreement with the selectivity predicted by the activation barrier trends.

中文翻译：

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氧化苄腈与不对称取代的降冰片烯和降冰片二烯的 1,3-偶极环加成反应的区域、立体和位点选择性：一项计算研究

在这项计算研究中，采用 M06/6-311G(d,p) 理论水平的密度泛函理论 (DFT) 计算来研究 1,3-偶极环加成的区域选择性、立体选择性和位点选择性氧化苄腈 (BNO) 与不对称取代的降冰片烯和降冰片二烯。在所有情况下，BNO 与不对称取代的 2-降冰片和不对称取代的 2-降冰片二烯之间的反应都伴随着 BNO 的氧攻击双键的受阻侧，除非引入了强 EWG。对于 BNO 和不对称取代的 2-降冰片二烯之间的反应，观察到不同程度的选择性取决于取代基，表明位点选择性在很大程度上受取代基性质的影响。一般来说，外型立体异构体通常优于内型立体异构体。亲电 (P _k ⁺ ) 和亲核 (P _k ^- ) Parr 函数计算与激活势垒趋势预测的选择性完全一致。