1,3-diethynylallenes : Stable monomers, length-defined oligomers, asymmetric synthesis, and optical resolution
1,3-diethynylallenes : Stable monomers, length-defined oligomers, asymmetric synthesis, and optical resolution
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DOI：
10.1002/ejoc.200700373
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发表时间：
2007-07
影响因子：
2.8
通讯作者：
M. T. Wiel;Severin Odermatt;P. Schanen;P. Seiler;F. Diederich
中科院分区：
文献类型：
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作者：
M. T. Wiel;Severin Odermatt;P. Schanen;P. Seiler;F. Diederich
合成了一系列不同取代的1，3-二乙炔基烯(DEAS)，证实了以前介绍的结构方案可以容忍多种官能团。新的DEAS含有至少一个极性基团，以促进手性固定相上的对映体拆分，并允许进一步的官能化。它们是热稳定和环境稳定的化合物，因为紧邻异丁烯部分的大体积取代基抑制了发生[2+2]环二聚化的趋势。在Gaser-Hay条件下，通过单体DEA的氧化偶联，得到了一系列长度定义的低聚物作为立体异构体的混合物。电子吸收数据表明，由于异构体π-体系的正交性，在低聚主链上缺乏扩展的π-电子共轭。值得注意的是，即使是立体异构体的复杂混合物也只产生一组单一的核磁共振信号，这突显了无环烯丙基乙酰基结构的低立体分化。DEAS的光学分辨率是一个惊人的挑战，报告了在分析水平上的初步结果。通过钯介导的Sn2‘-型交叉偶联反应将炔烃与光学纯的双丙叉烯前体进行不对称偶联，开辟了另一条具有光学活性的烯的合成途径，目前立体选择性高达78%ee。(Wiley-VCH Verlag GmbH&Co.KGaA，69451，德国温海姆，2007年)
A series of differently substituted 1,3-diethynylallenes (DEAs) have been synthesized, confirming that the previously introduced construction protocols tolerate a variety of functional groups. The new DEAs bear at least one polar group to facilitate enantiomer separations on chiral stationary phases and to allow further functionalization. They are thermally and environmentally stable compounds since bulky substituents next to the cumulene moiety suppress the tendency to undergo [2+2] cyclodimerization. A series of length-defined oligomers were obtained as mixtures of stereoisomers by oxidative coupling of a monomeric DEA under Glaser–Hay conditions. The electronic absorption data indicate a lack of extended π-electron conjugation across the oligomeric backbone due to the orthogonality of the allenic π-systems. Remarkably, even complex mixtures of stereoisomers only yield one single set of NMR signals, which underlines the low stereodifferentiation in acyclic allenoacetylenic structures. Optical resolution of DEAs represents an amazing challenge, and preliminary results on the analytical level are reported. Asymmetric synthesis by Pd-mediated SN2′-type cross-coupling of an alkyne to an optically pure bispropargylic precursor opens another promising route to optically active allenes with stereoselectivities currently reaching up to 78 % ee. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)