Improving reactivity and selectivity of aqueous-based Heck reactions by the local hydrophobicity of phosphine ligands

详细信息    查看全文

• 作者：Gina M. Roberts ; Shiyong Zhang ; Yan Zhao ; ^{zhaoy@iastate.edu" class="auth_mail" title="E-mail the corresponding author} ; L. Keith Woo ; ^{kwoo@iastate.edu" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Catalysis ; Selectivity ; Microenvironment ; Aqueous ; Hydrophobic effect
• 刊名：Tetrahedron
• 出版年：2015
• 出版时间：28 October 2015
• 年：2015
• 卷：71
• 期：43
• 页码：8263-8270
• 全文大小：1203 K

文摘

Modification of a triarylphosphine with a cholate moiety affords a new ligand, 1, which is effective in palladium-catalyzed Heck cross-couplings between acrylates and aryl iodides under mild, aqueous reaction conditions. High yields, up to 99%, were achieved in water at 40 °C. In competition studies, a more hydrophobic substrate (n-Bu acrylate) was preferred over the least hydrophobic substrate (methyl acrylate), supportive of a localized hydrophobic microenvironment near the catalytic center. The enhanced reactivity and selectivity for hydrophobic substrates disappeared when the local hydrophobicity was eliminated using a standard water-soluble phosphine or in organic solvents.