Mild, Efficient, and Robust Method for Stereocomplementary Iron-Catalyzed Cross-Coupling Using (E)- and (Z)-Enol Tosylates
作者:Yoo Tanabe、Hiroshi Nishikado、Hidefumi Nakatsuji、Kanako Ueno、Ryohei Nagase
DOI:10.1055/s-0030-1258131
日期:2010.9
Iron-catalyzed cross-coupling of Grignard reagents (RMgX) with (E)- and (Z)-enol tosylates proceeded smoothly to give a variety of the corresponding (E)- and (Z)-trisubstituted α,β-unsaturated methyl esters (total 30 examples; 55-98% yield). The simple, mild, stereoretentive method utilized iron(III) chloride (FeCl3), iron(III) acetylacetonate [Fe(acac)3], and iron(III) tris(dibenzylmethane) [Fe(dbm)3]. The (E)- and (Z)-enol tosylates were readily prepared by the reported stereocomplementary tosylation method from methyl β-keto esters or α-formyl esters. Methyl α-formyl esters were obtained via a practical and robust TiCl4-Et3N-mediated α-formylation of methyl esters with methyl formate.
铁催化的格氏试剂(RMgX)与(E)和(Z)-醇托烷基化合物的交叉耦合反应顺利进行,产生了多种相应的(E)和(Z)-三取代的α,β-不饱和甲基酯(共30个实例;产率55-98%)。该简单、温和、保持立体选择性的反应方法使用了氯化铁(FeCl3)、醋酸乙酯铁(Fe(acac)3)和铁(III)三(二苯基甲烷)[Fe(dbm)3]。而(E)和(Z)-醇托烷基化合物是通过已报道的立体互补托烷基化方法,从甲基β-酮酯或α-甲醛酯中方便制备的。甲基α-甲醛酯通过一种实用且稳健的TiCl4-Et3N催化的甲基酯与甲基甲酸酯的α-甲醛化反应获得。