AN ELECTRON-DONOR ACCEPTOR COMPLEX AND A THERMAL TRIPLEX AS INTERMEDIATES IN THE CYCLOADDITION REACTION OF N-VINYLCARBAZOLE WITH DIMETHYL 2,2-DICYANOETHYLENE-1,1-DICARBOXYLATE
AN ELECTRON-DONOR ACCEPTOR COMPLEX AND A THERMAL TRIPLEX AS INTERMEDIATES IN THE CYCLOADDITION REACTION OF N-VINYLCARBAZOLE WITH DIMETHYL 2,2-DICYANOETHYLENE-1,1-DICARBOXYLATE
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DOI：
10.1021/ja00004a035
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发表时间：
1991-02-13
影响因子：
15
通讯作者：
HALL, HK
中科院分区：
文献类型：
--
作者：
GOTOH, T;PADIAS, AB;HALL, HK
研究了N-乙烯基咔唑（NVCZ）与2，2-二氰基乙烯-1，1-二甲酸二甲酯在非极性和中等极性溶剂中通过四亚甲基两性离子中间体（T）生成1-（咔唑-9-基）-2，2-二氰基环丁烷-3，3-二甲酸二甲酯的反应动力学。 发现了两种竞争性T生成途径：（a）电子给体-受体（EDA）复合物的单分子转化和（B）EDA复合物与游离NVCZ之间的双分子反应。 这两个反应对总反应的贡献受溶剂和NVCZ浓度的影响。 三级动力学解释的基础上，阳离子自由基形式的过渡态的贡献，可以通过在热三链体中的电荷共振由额外的供体分子增强。 这可能是富电子不饱和分子与亲电试剂反应的一般催化模式。
The formation of dimethyl 1-(carbazol-9-yl)-2,2-dicyanocyclobutane-3,3-dicarboxylate through a tetramethylene zwitterionic intermediate (T) by the reaction of N-vinylcarbazole (NVCZ) and dimethyl 2,2-dicyanoethylene-1;1-dicarboxylate in nonpolar and moderately polar solvents was studied kinetically. Two competitive formation paths of T were found: (a) unimolecular transformations of the electron donor-acceptor (EDA) complex and (b) bimolecular reaction between the EDA complex and free NVCZ. Contributions of these two reactions to the overall reaction are influenced by the solvent and the concentration of NVCZ. The third-order kinetics is explained on the basis that the contribution of the cation-radical form to the transition state can be enhanced by an additional donor molecule through charge resonance in a thermal triplex. This may be a general mode of catalysis for reactions of electron-rich unsaturated molecules with electrophiles.