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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >How Do Nucleophiles Accelerate the Reactions of Dialkylstannylene Acetals? The Effects of Adding Fluoride to Dialkoxydi?n?butylstannanes
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How Do Nucleophiles Accelerate the Reactions of Dialkylstannylene Acetals? The Effects of Adding Fluoride to Dialkoxydi?n?butylstannanes

机译：亲核试剂如何促进二烷基亚锡缩醛的反应？在二烷氧基二正丁基锡烷中添加氟化物的作用

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Dialkylstannylene acetals are organotin intermediates widely used to facilitate regioselective monofunctionalization of diols or polyols by electrophiles. Alkylation is both the slowest and the most useful reaction of these intermediates, and this reaction is markedly accelerated by the addition of nucleophiles to the reaction media, usually cesium fluoride in dimethylformamide (DMF) or tetrabutylammonium iodide or bromide in toluene. The regioselectivity may be influenced by aggregation of the dialkylstannylene acetals into dimers and higher oligomers, and by the addition of these nucleophiles. The stabilities and the geometries of the species potentially involved in these processes were examined by using theoretical chemistry methods with di-n-butyldialkoxytin derivatives as examples and fluoride as the nucleophile. Geometry optimizations were performed at B3LYP/6-31G(d,p) level, and single point energies obtained at the MP2/6-311G(2d,p) level with diffuse functions added for fluorine. The LANL2DZdp basis set with diffuse and polarization functions and its effective core potential were used to describe tin. The addition of fluoride to monomeric di-n-butyldialkoxytin derivatives to give fluoridated monomers is predicted to be strongly exothermic, by 187 to 209 kJ/mol, depending on the alkoxyl group. The fluoridated monomers are calculated to react with monomers exothermically to give monofluoridated dimers, except for the di-t-butoxy derivative. Dimer formation on average is about 20 kJ mol~(?1) more exothermic than for the nonfluoridated monomers alone. Monofluoridated monomers strongly prefer to exist as monomers because the difluoridated dimers are estimated to be 209 to 278 kJ mol~(?1) less stable at 298 K.
机译：二烷基亚锡缩醛是有机锡中间体，广泛用于促进亲电试剂对二醇或多元醇的区域选择性单官能化。烷基化反应是这些中间体中最慢和最有用的反应，并且通过向反应介质中添加亲核试剂（通常为二甲基甲酰胺（DMF）中的氟化铯或碘化四丁基碘化铵或甲苯中的溴化物）显着促进该反应。区域选择性可能受二烷基亚锡缩醛缩合成二聚体和高级低聚物以及这些亲核试剂的添加的影响。通过使用理论化学方法，以二正丁基二烷氧基锡衍生物为例，以氟化物为亲核体，检查了可能涉及这些过程的物种的稳定性和几何形状。在B3LYP / 6-31G（d，p）的水平上进行了几何优化，在MP2 / 6-311G（2d，p）的水平上获得了单点能量，并为氟添加了扩散功能。具有扩散和极化功能的LANL2DZdp基集及其有效核心电势用于描述锡。氟化物加到单体二正丁基二烷氧基锡衍生物中以产生氟化单体，预计会强烈放热，取决于烷氧基基团，放热为187至209kJ / mol。计算出氟化单体与单体放热反应，得到单氟化二聚体，除了二叔丁氧基衍生物。平均二聚体的放热比单独的非氟化单体高约20 kJ mol·（？1）。单氟单体强烈倾向于以单体形式存在，因为据估计，二氟二聚体在298 K下的稳定性较差，为209至278 kJ mol〜（？1）。

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