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一些基于联烯的氟化学和自由基加成反应研究
Studies on Some Fluorine Chemistry and Free Radical Addition Reactions Ofallenes
【作者】 薛灿；
【作者基本信息】 浙江大学 ， 有机化学， 2014， 博士
【摘要】 联烯是一类特殊的三碳单元,具有1,2-累积二烯官能团,其末端两个碳可以分别装载两个取代基。本课题组对联烯化合物参与的反应进行了一些初步研究,主要包括联烯的亲核、亲电、自由基加成、过渡金属催化环化以及酶催化反应五类。在此基础上,我的博士论文着重围绕基于联烯的氟化学以及自由基加成反应展开,可以分为以下两部分：第一部分,一些基于联烯的氟化学及其应用研究1.发展了多取代全氟烷基取代呋喃和全氟烷基呋喃基酮的有效合成方法。其中包括两部分内容：(a)对于全取代联烯基全氟烷基酮,可以通过控制TfOH的用量、反应温度以及是否加入H20调控反应生成单一的2-全氟烷基呋喃和全氟烷基呋喃基酮。(b)在AuCl催化下三取代联烯基全氟烷基酮发生高效的异构环化反应得到2-全氟烷基呋喃；向反应体系中继续投入TfOH和定量H20,在两步一锅法的合成策略下,联烯基酮可以发生串联的异构环化-水解脱氟反应产生全氟烷基呋喃基酮。根据机理实验和18O标记研究,酸催化下全氟烷基呋喃可以发生水解脱氟反应生成相应的全氟烷基呋喃基酮,酮羰基中的氧被证实来自于水分子。2.实现了基于单取代和1,1-双取代联烯的高效、高区域选择性的碘氟化反应。对联烯的碘氟化反应产物的应用研究表明,2-碘代烯丙基氟化物可以作为有用的有机合成砌块。第二部分,联烯参与的自由基加成反应研究发展了基于单联烯的高区域和立体选择性的硝化-氧胺化反应,该反应经历了自由基加成历程并且一步构筑了C-N键和C-O键。单联烯的硝化-氧胺化反应底物适用范围较广,可以兼容众多的的官能团和杂环；硝化-氧胺化产物可作为有用的合成子。这一反应转化为合成结构复杂的化合物提供了有效的合成策略。此外,在本组何广科博士发展的高效合成多取代联烯基全氟烷基酮的方法基础上,我们成功将此合成策略由联烯酸酯推广到α,β-不饱和羧酸酯、炔酸酯以及普通羧酸酯,通过和全氟烷基格氏试剂发生1,2-加成反应高效地制备得到相应的全氟烷基酮类化合物。
【Abstract】 Allenes are a class of compounds with a cumulated three-carbon unit bearing a remarkable substituent-loading capability. Much effort has already been made towards the nucleophilic additions, electrophilic additions, free radical additions, transition metal-catalyzed cyclizations, and enzyme-catalyzed reactions of allenes in our group. Based on these studies, the main theme of my dissertation may be divided into the following two parts:Part Ⅰ:Studies on some fluorine chemistry of allenes1. We have developed an efficient methodology for preparation of multi-substituted2-perfluoroalkyl furans and furan-2-yl perfluoroalkyl ketones:(a)2-perfluoroalkyl furans or furan-2-yl perfluoroalkyl ketones could be obtained highly selectively by adjusting the reaction conditions, such as the dosage of TfOH and H2O, and reaction temperature, from fully-substituted allenyl perfluoroalkyl ketones.(b)2-perfluoroalkyl furans could be efficiently prepared from cycloisomerization of tri-substituted allenyl perfluoroalkyl ketones with AuCl as the catalyst; in the spirit of the two-steps in one pot synthetic strategy, addition of TfOH and water into the same vessel would generate corresponding furan-2-yl perfluoroalkyl ketones through the tandem cycloisomerization-hydrolytic defluorination of allenyl perfluoroalkyl ketones. The oxygen atom of the carbonyl group of the newly formed furan-2-yl perfluoroalkyl ketones originates from the water according to the18O isotopic study.2. We have developed a highly regioselective iodofluorination reaction of mono-substituted and geminally disubstituted allenes, affording2-iodoallylic fluorides which have been demonstrated to be very attractive building blocks in organic synthesis. Part II:Studies on the free radical addition reactions of allenesWe have developed a highly regio-and stereoselective nitro-oxoamination reaction of mono-allenes via a radical process to form C-N and C-O bonds in one step, which could tolerate various functional groups and heterocycles affording a series of useful building blocks. This conversion would offer a practical strategy for the synthesis of intricate structure.In addition, we have realized the efficient preparation of perfluoroalkyl ketones via the1,2-addition reactions of alkenoates, alkynoates, and normal carboxylic acid esters with perfluoroalkyl Grignard reagents based on the synthetic methodology developed previously by Dr. He Guangke in our group.