Asymmetric synthesis of trifluoromethyl substituted dihydropyrans via organocatalytic cascade Michael–hemiketalization reaction
作者:Jin-jia Wang、Zhi-peng Hu、Chun-liang Lou、Jun-liang Liu、Xue-ming Li、Ming Yan
DOI:10.1016/j.tet.2011.04.086
日期:2011.6
Asymmetric conjugate addition of ethyl 4,4,4-trifluoroacetoacetate and other trifluoromethyl substituted nucleophiles to β,γ-unsaturated α-keto esters has been developed. The reaction efficiently provided dihydropyrans via cascade Michael–hemiketalization pathways. Quinine-derived thiourea was identified to be the best catalyst. A number of trifluoromethyl substituted dihydropyrans with three consecutive
已经开发了4,4,4-三氟乙酰乙酸乙酯和其他三氟甲基取代的亲核试剂向β,γ-不饱和α-酮酯的不对称共轭加成。该反应通过级联的迈克尔-半缩酮化途径有效地提供了二氢吡喃。奎宁衍生的硫脲被认为是最好的催化剂。获得了许多具有三个连续手性中心的三氟甲基取代的二氢吡喃,具有优异的收率,非对映选择性和对映选择性。产物容易转化为相应的四氢吡啶,而没有光学纯度的损失。