Trifluoroacetylation of unsymmetrical ketone acetals. A convenient route to obtain alkyl side chain trifluoromethylated heterocycles
作者:Helio G Bonacorso、Marcos A.P Martins、Sandra R.T Bittencourt、Rogério V Lourega、Nilo Zanatta、Alex F.C Flores
DOI:10.1016/s0022-1139(99)00146-3
日期:1999.11
A convenient method to obtain β-alkyl-β-methoxyvinyl trifluoromethyl ketones [CF3COCHC(OMe)R, where R = Et, n-Pr, i-Pr, i-Bu, t-Bu, –(CH2)2OMe] from the regiospecific acylation of kinetic enol ether generated in situ is reported. The unsymmetrical ketone dimethyl acetals react with trifluoroacetic anhydride in the presence of pyridine using dry chloroform as solvent with a temperature range of 25–60°C
一种方便的方法来获得β-烷基-β-甲氧基乙烯基三氟甲基酮[CF 3 COCHeC(OMe)R,其中R = Et,n -Pr,i -Pr,i -Bu,t-Bu,–(CH 2)2 OMe]来自原位产生的动力学烯醇醚的区域特异性酰化。在吡啶存在下,使用干燥的氯仿作为溶剂,在25–60°C的温度范围内,不对称的酮二甲基乙缩醛与三氟乙酸酐反应。这些缩醛[RC-(OMe)2 Me]是由烷基甲基酮与原甲酸三甲酯在p的存在下反应制得的以甲苯磺酸为催化剂,以纯甲醇为溶剂。事实证明,新的乙酰化烯醇醚是构建有趣的烷基三氟甲基取代杂环的通用构建基。因此,已以高收率(62–79%)获得了异恶唑啉,吡唑啉,吡唑和嘧啶酮的实例。