Preparation of monodentate phosphinite ligands: their applications in palladium catalyzed Suzuki reactions

详细信息    查看全文

• 作者：Yan-Huei Cheng ; Chia-Ming Weng ; Fung-E. Hong
• 关键词：Phosphinite ; Palladium complex ; Suzuki cross-coupling reaction ; Orthometallation ; Dimeric ; Monomeric
• 刊名：Tetrahedron
• 出版年：2007
• 出版时间：10 December 2007
• 年：2007
• 卷：63
• 期：50
• 页码：12277-12285
• 全文大小：814 K

文摘

Two phosphinites 2,6-OMe, 4-Me, 1-OPR₂C₆H₂ (5a: R=Ph; 5b: R=^tBu) were prepared in good yields. Two methoxy groups are placed on the 2,6 positions of the phosphinites deliberately thereby to avoid a plausible orthometallation process while coordinating toward palladium metal. Further reaction of 5a with PdCl₂ in the ratio of 2:1 and 1:1 gave 5a ligated palladium complexes {(5a)PdCl(μ-Cl)}₂ 7a and {(5a)₂PdCl₂} 8a, respectively. As revealed from their crystal structures, the former is a dimeric complex with anticipated molecular arrangement; nevertheless, the latter is a monomeric complex with unexpected, energetically unfavorable cis form. By contrast, only dimeric form was observed from the reaction of 5b with PdCl₂. It is believed that the bulky substituents, ^tBu, on 5b prevent the formation of a monomeric complex in cis form. Fair to good efficiencies were observed for the Suzuki–Miyaura cross-coupling reactions employed in situ-prepared 5/Pd(OAc)₂ as the catalytic precursor.