Direct Synthesis of NNN-Donor Enantiopure Scorpionate Ligands by an Efficient Diastereoselective Nucleophilic Addition to Imines

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• 作者：Antonio Otero ; Juan Ferna虂ndez-Baeza ; Juan Tejeda ; Agusti虂n Lara-Sa虂nchez ; Sonia Franco ; Jaime Marti虂nez-Ferrer ; Mari虂a P. Carrio虂n ; I. Lo虂pez-Solera ; Ana M. Rodri虂guez ; Luis F. Sa虂nchez-Barba
• 刊名：Inorganic Chemistry
• 出版年：2011
• 出版时间：March 7, 2011
• 年：2011
• 卷：50
• 期：5
• 页码：1826-1839
• 全文大小：1233K
• 年卷期：v.50,no.5(March 7, 2011)
• ISSN：1520-510X

文摘

New enantiopure imines (1鈭?b>9) with a chiral substrate to control the stereochemistry of a newly created stereogenic center have been synthesized by reaction of the commercially available (1R)-(鈭?-myrtenal and different primary amines. The diastereomerically enriched lithium-scorpionate compounds [Li(魏³-mbpza)(THF)] (10) (mbpza = N-p-methylphenyl-(1R and 1S)-1-[(1R)-6,6-dimethylbicyclo[3.1.1]-2-hepten-2-yl]-2,2-bis(3,5-dimethylpyrazol-1-yl)ethylamide), [Li(魏³-mobpza)(THF)] (11) (mobpza = N-p-methoxyphenyl-(1R and 1S)-1-[(1R)-6,6-dimethylbicyclo[3.1.1]-2-hepten-2-yl]-2,2-bis(3,5-dimethylpyrazol-1-yl)ethylamide), [Li(魏³-fbpza)(THF)] (12) (fbpza = N-p-fluorophenyl-(1R and 1S)-1-[(1R)-6,6-dimethylbicyclo[3.1.1]-2-hepten-2-yl]-2,2-bis(3,5-dimethylpyrazol-1-yl)ethylamide), and [Li(魏³-clbpza)(THF)] (13) (clbpza = N-p-chlorophenyl-(1R and 1S)-1-[(1R)-6,6-dimethylbicyclo[3.1.1]-2-hepten-2-yl]-2,2-bis(3,5-dimethylpyrazol-1-yl)ethylamide) were obtained by a diastereoselective 1,2-addition of an organolithium reagent to imines in good yield and with good diastereomeric excess (ca. 80%). The complexes [LiCl(魏²-R,R-fbpzaH)(THF)] (14) and [LiCl(魏²-R,R-clbpzaH)(THF)] (15) were obtained in enantiomerically pure form by the treatment of THF solutions of 12 or 13 with NH₄Cl. The enantiomerically pure amines (R,R-mbpzaH) (16), (R,R-mobpzaH) (17), (R,R-fbpzaH) (18), and (R,R-clbpzaH) (19) were obtained by hydrolysis of the lithium-scorpionate compounds 10鈭?b>13 with H₂O. The lithium compound 12 was reacted with [TiCl₄(THF)₂] or [ZrCl₄] to give the enantiopure complexes [MCl₃(魏³-R,R-fbpza)] [M = Ti (20), Zr (21)]. The amine compound 18 reacted with [MX₄] (M = Ti, X = OⁱPr, OEt; M = Zr; X = NMe₂) to give the complexes [MX₃(魏³-R,R-fbpza)] (22鈭?b>24). The reaction of Me₃SiCl with [Zr(NMe₂)₃(魏³-R,R-fbpza)] (24) in different molar ratios led to the halide-amide-containing complexes [ZrCl(NMe₂)₂(魏³-R,R-fbpza)] (25) and [ZrCl₂(NMe₂)(魏³-R,R-fbpza)] (26) and the halide complex 21. The isolation of only one of the three possible diastereoisomers of complexes 25 and 26 revealed that chiral induction from the ligand to the zirconium center took place. The structures of these compounds were elucidated by ¹H and ¹³C{¹H} NMR spectroscopy, and the X-ray crystal structures of 5, 12, 14, 15, and 24 were also established.