Stereospecific Friedel-Crafts alkylation of aromatic compounds: synthesis of optically active 2- and 3-arylalkanoic esters
摘要:
The alkylation of aromatic compounds, such as benzene, toluene, chlorobenzene, and naphthalene, with optically active (S)-alkyl 2-(sulfonyloxy)propionates and (R)-alkyl 3-(sulfonyloxy)butanoates in the presence of AlCl3 afforded optically active (S)-alkyl 2-arylpropionates and (S)-alkyl 3-arylbutanoates in fair to good chemical yields (40-84%) and in good to excellent optical yields (61-97%). As usually occurs in Friedel-Crafts alkylation reactions, poor regioselectivity was observed.
A chiralligand, a catalytic amount of lithium cation, and no chiral proton source: These are features of the present asymmetric addition-protonation of propenoates with 2-trimethylsilylbenzenethiol. The reaction is catalyzed by a combination of lithium 2-trimethylsilylbenzenethiolate and the chiralligand 1. Desulfurization of the product affords 2-substituted propanoates with high ee values and without
Stereoselective Ketone Rearrangements with Hypervalent Iodine Reagents
作者:Florence Malmedy、Thomas Wirth
DOI:10.1002/chem.201603022
日期:2016.11.2
The first stereoselective version of an iodine(III)‐mediated rearrangement of arylketones in the presence of orthoesters is described. The reaction products, α‐arylated esters, are very useful intermediates in the synthesis of bioactive compounds such as ibuprofen. With chiral lactic acid‐based iodine(III) reagents product selectivities of up to 73 % ee have been achieved.
An Enantioselective, Intermolecular α-Arylation of Ester Enolates To Form Tertiary Stereocenters
作者:Zhiyan Huang、Zheng Liu、Jianrong (Steve) Zhou
DOI:10.1021/ja2066829
日期:2011.10.12
asymmetric α-arylation of carbonylcompounds, formation of tertiary centers with high enantioselectivity is a longstanding problem, due to easy enolization of the monoarylation products. Herein, we report such examples using a palladium catalyst supported by a new, (R)-H(8)-BINOL-derived monophosphine. Silyl ketene acetals, together with a weakly basic activator, were used as equivalents of ester anions
在过渡金属催化的羰基化合物的不对称α-芳基化中,由于单芳基化产物容易烯醇化,形成具有高对映选择性的三级中心是一个长期存在的问题。在此,我们报告了使用由新的 (R)-H(8)-BINOL 衍生的单膦支持的钯催化剂的示例。甲硅烷基乙烯酮缩醛与弱碱性活化剂一起用作酯阴离子的等价物,它们与芳基三氟甲磺酸酯以优异的对映体过量 (ee) 顺利反应。该反应的有效性在 92% ee 的 (S)-萘普生的克级合成中得到证明。
Pd/Josiphos-Catalyzed Enantioselective α-Arylation of Silyl Ketene Acetals and Mechanistic Studies on Transmetalation and Enantioselection
5-MePh)2PF-Pcy2) catalyzed the enantioselective arylation of silyl keteneacetals with iodoarenes in the presence of TlOAc to promote transmetalation of silyl keteneacetals. The highest enantioselectivities giving α-arylesters up to 91% ee were achieved when (E)-1-methoxy-1-(trimethylsiloxy)propene (E/Z = 88/12) was used for the silyl keteneacetal. The effect on enantioselection of a chiral ligand is discussed
在TlOAc存在下,钯/(4-MeO-3,5-MePh)2 PF-Pcy 2)催化硅烷基乙烯酮缩醛与碘芳烃的对映选择性芳基化,以促进硅烷基乙烯酮缩醛的金属转移。当将(E)-1-甲氧基-1-(三甲基甲硅烷氧基)丙烯(E / Z = 88/12)用于甲硅烷基烯酮缩醛时,可获得最高91%ee的α-芳基酯的最高对映选择性。基于钯/(4-MeO-3,5-MePh)2 PF-Pcy 2)配合物的X射线结构以及DFT在机械方面的计算研究结果,讨论了对手性配体对映体选择的影响催化循环。