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Solvent-free Catalytic Reaction : Ideal Green Reaction Using Silicon Catalysts with Weakly Coordinating Anion

无溶剂催化反应：使用弱配位阴离子硅催化剂的理想绿色反应

基本信息

批准号：
15350062
负责人：
HATANAKA Yasuo
金额：
$ 8.32万
依托单位：
Osaka City University (2004-2005)Osaka Prefecture University (2003)
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2003
资助国家：
日本
起止时间：
2003 至 2005
项目状态：
已结题

项目摘要

Chloride abstraction from pentacoordinate chlorosilanes by sodium or cesium salts of weakly coordinating anions such as B[3,5-(CF_3)_2CoH_3]_4- (TFPB) and carabadodecaborate gave tetracoordinate silyl cations having intramolecularly coordinating amide groups. X-ray structure analysis of these salts indicates the near-planar geometries at the silicon atoms reflecting sp^2 planarity and markedly long Si-O bond distances. The positive charge located in the silicon atoms would be stabilized by weak intramolecular O□Si coordination. The ^<29>Si NMR spectra also support silylium ion character of the silicon atoms. These salts exhibit effective catalytic activity as Lewis acid to promote the cross-aldol reaction between silyl enol ethers and less reactive carbonyl compounds such as ketones and aliphatic aldehydes, affording high yields of the corresponding aldol adducts. Furthermore, cationic silicon species, which were generated in situ by protodesilylation of silicon enolates with [H(OEt_2)_2]+[B(C_6F_5)_4]-, exhibited high catalytic activity as a Lewis acid in the aldol reaction of ketones with silicon enolates under the solvent-free conditions. Thus, sterically hindered less reactive ketones smoothly reacted with silicon enolates in the presence of cationic silicon catalyst, giving aldol products in high yields. Silyl cations, which were prepared from 5-coordinate chlorosilanes, showed high catalytic activity in promoting the Michael addition of silicon enolates to α,β-unsaturated carbonyl compounds or nitriles.

用B[3，5-(CF_3)_2CoH_3]_4-(TFPB)等弱配位阴离子的钠盐或铯盐和十二硼碳酸盐从五配位氯硅烷中抽提氯，得到具有分子内配位基团的四配位硅基阳离子。这些盐的X射线结构分析表明，硅原子的近平面几何构型反映了sp2的平面性和明显的较长的Si-O键距。分子内较弱的O-Si配位可以稳定位于硅原子中的正电荷。~&lt；29&gt；Si的核磁共振谱也支持硅原子的硅离子特征。这些盐表现出作为Lewis酸的有效催化活性，可以促进硅烯醇醚与活性较低的酮和脂肪醛之间的交叉Aldol反应，从而提供相应的Aldol加合物的高产率。此外，在无溶剂条件下，[H(OEt_2)_2]+[B(C_6F_5)_4]-原位脱硅生成的阳离子硅物种在酮与硅烯醇酸盐的Aldol反应中表现出很高的Lewis酸催化活性。因此，在阳离子硅催化剂的存在下，空间受阻较少的反应酮与硅烯醇酸盐顺利反应，得到高产率的羟醛产品。由5配位的氯硅烷合成的硅基阳离子对α，β不饱和的羰基化合物或腈类化合物的迈克尔加成反应表现出很高的催化活性。