E- or Z-selective knoevenagel condensation of acetoacetic derivatives:: Effect of acylated substituent, that is, TEMPO and amines, as an auxiliary, and new accesses to trisubstituted E- and Z-2-alkenals and furans
E- or Z-selective knoevenagel condensation of acetoacetic derivatives:: Effect of acylated substituent, that is, TEMPO and amines, as an auxiliary, and new accesses to trisubstituted E- and Z-2-alkenals and furans
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DOI：
10.1021/jo051952w
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发表时间：
2006-02-03
影响因子：
3.6
通讯作者：
Kawafuchi, H
中科院分区：
文献类型：
--
作者：
Inokuchi, T;Kawafuchi, H
O-乙酰乙酰基TEMPO（2，2，6，6-四甲基哌啶-1-氧基）与被吸电子基团取代的醛如芳族和杂芳族醛的Knoevenagel缩合优先导致E-加合物，而酰基乙酰胺包括Weinreb酰胺仅产生Z-加合物。这些E-和Z-加合物通过用DIBALH逐步还原酰基，然后在羟基保护后还原羧基官能团，分别选择性地转化为相应的（2 E）-和（2 Z）-2-羟烷基-2-烯醛。还开发了利用E-几何构型将Knoevenagel产物转化为三取代呋喃的方法。
Knoevenagel condensation of O-acetoacetylTEMPOs (2,2,6,6-tetramethylpiperidine-1-oxyl) with aldehydes substituted with an electron-withdrawing group such as aromatic and heteroaromatic ones leads preferentially to E-adducts, while acylacetoamides including Weinreb amides produce Z-adducts, exclusively. These E- and Z-adducts are selectively converted to the corresponding (2E)- and (2Z)-2hyroxyalkyl-2-alkenals, respectively, by stepwise reductions of the acyl group with DIBALH and then the carboxylic functions after protection of the hydroxy group. Transformation of the Knoevenagel products by taking advantage of the E-geometry to trisubstituted furans is also developed.