Pyridyl group assisted deprotonation of a methyl group on silicon: Complex induced proximity effect and novel hydroxymethylation
Pyridyl group assisted deprotonation of a methyl group on silicon: Complex induced proximity effect and novel hydroxymethylation
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DOI：
10.1021/jo015528g
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发表时间：
2001-06-01
影响因子：
3.6
通讯作者：
Yoshida, J
中科院分区：
文献类型：
--
作者：
Itami, K;Kamei, T;Yoshida, J
开发了一种硅上甲基去质子化的新方法。这种新开发的 cr-锂化方案基于分子内吡啶基配位，以稳定 a-甲硅烷基碳负离子以及固有的硅 a 效应。研究发现，2-吡啶基三甲基硅烷会发生去质子化（t-BuLi/Et(2)O/-78℃），但其他相关硅烷如苯基三甲基硅烷、3-吡啶基三甲基硅烷和4-吡啶基三甲基硅烷不会发生去质子化。这种去质子化似乎是通过硅上 2-吡啶基的络合物诱导邻近效应 (CIPE) 进行的。 (1)H NMR 分析(2-吡啶基二甲基甲硅烷基)甲基锂揭示了吡啶基与锂的分子内配位。 (2-吡啶基二甲基甲硅烷基)-甲基锂被发现可以与氯硅烷、氢硅烷、氯锡烷、溴、碘、有机溴化物、醛和酮反应，产率良好至优异。所得加合物进一步用H(2)O(2)/KF氧化，以优异的收率得到相应的醇。因此，这种两步转化提供了一种有效的亲核羟甲基化方法。
A novel methodology for the deprotonation of a methyl group on silicon has been developed. This newly developed cr-lithiation protocol is based on the intramolecular pyridyl group coordination to stabilize the a-silyl carbanion together with the inherent silicon a effect. It was found that the deprotonation (t-BuLi/Et(2)O/-78 degreesC) occurs with 2-pyridyltrimethylsilane but not with other related silanes such as phenyltrimethylsilane, 3-pyridyltrimethylsilane, and 4-pyridyltrimethylsilane. It seems that this deprotonation proceeded through the agency of the complex-induced proximity effect (CIPE) of a 2-pyridyl group on silicon. (1)H NMR analysis of (2-pyridyldimethylsilyl)methyllithium revealed the intramolecular coordination of a pyridyl group to lithium. ( 2-Pyridyldimethylsilyl)-methyllithium was found to react with chlorosilanes, hydrosilanes, chlorostannanes, bromine, iodine, organic bromides, aldehydes, and ketones in good to excellent yields. The resultant adducts were further oxidized with H(2)O(2)/KF to give the corresponding alcohols in excellent yields. Thus, this two-step transformation provides an efficient method for the nucleophilic hydroxymethylation.