Mechanism and ligand-transfer selectivity of 1,2-addition of organozincate complexes to aldehyde.
Mechanism and ligand-transfer selectivity of 1,2-addition of organozincate complexes to aldehyde.
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DOI：
10.1021/ja048663u
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发表时间：
2004-08
影响因子：
15
通讯作者：
M. Uchiyama;Shinji Nakamura;T. Ohwada;Masaharu Nakamura;E. Nakamura
中科院分区：
文献类型：
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作者：
M. Uchiyama;Shinji Nakamura;T. Ohwada;Masaharu Nakamura;E. Nakamura
用密度泛函理论（DFT）研究了有机锌酸酯与羰基化合物的1，2-加成反应的反应活性和配体转移选择性的起源。与Me（2）Zn相比，Me（3）ZnLi与甲醛的加成反应的研究表明，刘易斯酸性Li原子和带负电荷的Me（3）Zn部分的推拉协同作用促进了加成反应。这个分析然后提供了一个答案的机制问题，实验上建立的配体转移选择性的1，2-加成的杂配位有机锌酸盐Me（2）Zn（X）Li（X = H-，R（2）N-，和R（3）Si-）。这些杂配位锌酸盐化合物的加入导致H、R（2）N和R（3）Si基团的选择性转移，这是由于这些基团与羰基π系统之间的有利轨道相互作用。锌酸盐化合物的加成反应符合常规亲核反应的机理框架，例如MeLi二聚体的加成反应，并且不同于其中涉及铜原子的氧化/还原的有机铜酸盐的反应。
Density functional theory (DFT) calculations have been performed to investigate the origin of the reactivity and ligand-transfer selectivity of organozincates in the 1,2-addition to carbonyl compounds. Examination of the addition of Me(3)ZnLi to formaldehyde as compared with that of Me(2)Zn showed that the addition reaction is facilitated by the push-pull synergy of the Lewis acidic Li atom and the negatively charged Me(3)Zn moiety. This analysis then provided an answer to the mechanistic question about the experimentally established ligand-transfer selectivity in the 1,2-addition of heteroleptic organozincate Me(2)Zn(X)Li (X = H-, R(2)N-, and R(3)Si-). The addition of these heteroleptic zincate compounds results in selective transfer of H, R(2)N, and R(3)Si groups owing to the favorable orbital interaction between these groups and the carbonyl pi-system. The addition reaction of the zincate compounds conforms to the mechanistic framework of the conventional nucleophilic reaction, such as the addition reaction of MeLi dimer, and is different from the reaction of organocuprates, where oxidation/reduction of the copper atom is involved.