Practical and robust method for stereoselective preparations of ketene silyl (thio)acetal derivatives and NaOH-catalyzed crossed-Claisen condensation between ketene silyl acetals and methyl esters
作者:Kenta Takai、Yuuya Nawate、Tomohito Okabayashi、Hidefumi Nakatsuji、Akira Iida、Yoo Tanabe
DOI:10.1016/j.tet.2009.02.084
日期:2009.7
NaHMDS–2TMSCl). The first catalytic NaOH-catalyzed crossed-Claisen condensation between ketene silyl acetals and methyl esters proceeded successfully to give a variety of α-monomethyl β-ketoesters and inaccessible α,α-disubstituted β-ketoesters. For further extension, a couple of Claisen-aldol tandem reactions of the obtained β-ketoester analogues utilizing TiCl4 and TiCl4–Bu3N reagents smoothly proceeded
我们开发了的(立体选择性制剂的高效,实用,和稳健的方法Ž从硫酯和烷基(1个)三甲基甲硅烷-ketene(TMS)硫缩醛Ž) -或(1个Ž,3 é烷基β-酮酸酯的-1,3-bis(TMS)二烯醇醚。前一种制备是通过简便的方法(LDA–TMSCl,0–5°C,2.5 h)进行的,而后一种制备则涉及便捷的方法A(2NaHMDS–2TMSCl)和经济高效的方法B(NaH,NaHMDS–2TMSCl)。烯酮甲硅烷基缩醛与甲酯之间的首次NaOH催化催化的交叉克莱森缩合反应成功进行,得到了各种α-单甲基β-酮酸酯和难以获得的α,α-二取代的β-酮酸酯。为了进一步扩展,利用TiCl 4和TiCl 4 -Bu 3 N试剂对获得的β-酮酸酯类似物进行了几次克莱森-醛醇串联反应,并顺利进行了很好的立体选择性。