銀催化端炔類反應(yīng)機(jī)理的研究
發(fā)布時(shí)間：2019-06-30 21:40
【摘要】：銀鹽具有催化活性高、路易斯酸特性和價(jià)格低廉等優(yōu)點(diǎn),且可以有效地避免其他過(guò)渡金屬催化端炔易于偶聯(lián)的弊端。因此,銀催化端炔類反應(yīng)成為近年來(lái)有機(jī)合成的熱點(diǎn)研究領(lǐng)域。理論與計(jì)算化學(xué)在闡明反應(yīng)、特別是有機(jī)反應(yīng)機(jī)理方面發(fā)揮著巨大的作用,已成為探究反應(yīng)歷程不可或缺的重要手段。本論文中,我們主要采用密度泛函方法探討催化劑及實(shí)驗(yàn)反應(yīng)條件(如底物、配體、溶劑及痕量水等)對(duì)機(jī)理的影響,從而揭示一價(jià)銀鹽獨(dú)特的催化作用及其高的催化活性本質(zhì)。主要研究?jī)?nèi)容如下：1.將密度泛函理論(DFT)與實(shí)驗(yàn)結(jié)合闡明了異腈-炔環(huán)加成的反應(yīng)機(jī)理,詳細(xì)探究了反應(yīng)條件對(duì)機(jī)理的影響。發(fā)現(xiàn)該反應(yīng)是一個(gè)新穎的多組分(Ag_2CO_3,溶劑和底物)催化的自由基機(jī)理,主要包含異腈自由基的形成,異腈自由基與炔銀的環(huán)加成,含銀五元環(huán)的質(zhì)子化和氫遷移四個(gè)過(guò)程。第二過(guò)程中C2-C4鍵的形成是反應(yīng)的決速步,所需活化自由能能壘(△△G(?))為10.2kcal/mol。催化劑Ag_2CO_3在異腈自由基的形成過(guò)程中具有雙重作用：作拔取異腈Cα原子上質(zhì)子的堿和形成異腈自由基的引發(fā)劑。異腈和溶劑1,4-二氧六烷作質(zhì)子給體實(shí)現(xiàn)含銀五元環(huán)質(zhì)子化的同時(shí)獲得相應(yīng)的自由基物種,1,4-二氧六烷可以作自由基傳遞體引發(fā)異腈自由基的形成。此外,1,4-二氧六烷作助劑和質(zhì)子給體/受體,有效地降低氫遷移過(guò)程活化能壘而明顯增加反應(yīng)活性。該發(fā)現(xiàn)為過(guò)渡金屬銀鹽催化含異腈或炔類反應(yīng)提供新的機(jī)理的見(jiàn)解,為銀鹽催化反應(yīng)條件的優(yōu)化提供新思路。2.采用DFT方法探究了利用水和碳酸銀共催化端炔的氫疊氮化合成烯基疊氮的詳細(xì)反應(yīng)機(jī)理。研究發(fā)現(xiàn)該反應(yīng)主要經(jīng)歷Ag_2CO_3與底物TMS-N_3配位促進(jìn)水與TMS-N_3反應(yīng)生成HN_3、水協(xié)助Ag_2CO_3對(duì)端炔去質(zhì)子化形成炔銀、HN_3與炔銀的選擇性加成和AgHCO_3對(duì)端碳原子質(zhì)子化四個(gè)過(guò)程形成烯基疊氮產(chǎn)物。第三步中C-N鍵的形成是該反應(yīng)的決速步。反應(yīng)中水作HN_3的氫源和質(zhì)子傳遞體。計(jì)算結(jié)果表明Ag_2CO_3對(duì)底物的調(diào)控模式包括Ag_2CO_3-配位、Ag_2CO_3-成鍵及兩者的互相轉(zhuǎn)化。該反應(yīng)的區(qū)域選擇性遵循馬氏規(guī)則,很好地解釋了實(shí)驗(yàn)觀測(cè)。我們的計(jì)算為銀-催化端炔的氫疊氮化反應(yīng)提供合適的機(jī)理,為實(shí)驗(yàn)研究者提供理論基礎(chǔ)。
[Abstract]:Silver salt has the advantages of high catalytic activity, Lewis acid characteristics and low price, and can effectively avoid the disadvantages that other transition metal catalytic terminal alkynes are easy to be coupled. Therefore, silver catalyzed alkynes have become a hot research field in organic synthesis in recent years. Theoretical and computational chemistry plays an important role in illustrating the reaction, especially the mechanism of organic reaction, and has become an indispensable means to explore the reaction process. In this thesis, we mainly use density functional method to investigate the effects of catalysts and experimental reaction conditions (such as substrate, ligands, solvents and trace water, etc.) on the mechanism, so as to reveal the unique catalytic effect of monovalent silver salt and its high catalytic activity. The main research contents are as follows: 1. The density functional theory (DFT) was combined with experiments to clarify the reaction mechanism of isonitrile-alkynes cycloaddition, and the effect of reaction conditions on the mechanism was investigated in detail. It is found that the reaction is a novel free radical mechanism catalyzed by multicomponent (Ag_2CO_3, solvent and substrate), which mainly includes four processes: the formation of isonitrile radical, the cycloaddition of isonitrile radical and silver alkyne, the protonation and hydrogen migration of five-component ring containing silver. In the second process, the formation of C2-C4 bond is the decisive step of the reaction, and the required activation free energy barrier (G (?) It is 10.2 kcal mol. The catalyst Ag_2CO_3 plays a dual role in the formation of isonitrile radical: it is used as an initiator for the extraction of protons on isonitrile C 偽 atom and the formation of isonitrile radical. Isonitrile and solvent 1,4-dioxane were used as proton donors to realize silver pentagonal cycloprotonization at the same time, and the corresponding free radical species were obtained. 1, 4-dioxane can be used as free radical transporter to initiate the formation of isonitrile radical. In addition, 1, 4-dioxane as promoter and proton donor / receptor can effectively reduce the activation energy barrier during hydrogen migration and increase the reaction activity. This finding provides a new idea for the catalytic reaction of isonitrile or alkynes catalyzed by transition metal silver salt, and provides a new idea for the optimization of catalytic reaction conditions of silver salt. 2. The mechanism of hydroazide synthesis of alkenyl azide catalyzed by water and silver carbonate was investigated by DFT. It was found that the reaction was mainly through the coordination of Ag_2CO_3 with substrate TMS-N_3 to promote the reaction of water with TMS-N_3 to form HN_3, water to assist Ag_2CO_3 in the protonation of terminal alkynes to form silver alkynes. The selective addition of HN_3 with acetylene silver and the protonation of AgHCO_3 to terminal carbon atoms formed alkenyl azide products. In the third step, the formation of C 鈮，
本文編號(hào)：2508278
[Abstract]:Silver salt has the advantages of high catalytic activity, Lewis acid characteristics and low price, and can effectively avoid the disadvantages that other transition metal catalytic terminal alkynes are easy to be coupled. Therefore, silver catalyzed alkynes have become a hot research field in organic synthesis in recent years. Theoretical and computational chemistry plays an important role in illustrating the reaction, especially the mechanism of organic reaction, and has become an indispensable means to explore the reaction process. In this thesis, we mainly use density functional method to investigate the effects of catalysts and experimental reaction conditions (such as substrate, ligands, solvents and trace water, etc.) on the mechanism, so as to reveal the unique catalytic effect of monovalent silver salt and its high catalytic activity. The main research contents are as follows: 1. The density functional theory (DFT) was combined with experiments to clarify the reaction mechanism of isonitrile-alkynes cycloaddition, and the effect of reaction conditions on the mechanism was investigated in detail. It is found that the reaction is a novel free radical mechanism catalyzed by multicomponent (Ag_2CO_3, solvent and substrate), which mainly includes four processes: the formation of isonitrile radical, the cycloaddition of isonitrile radical and silver alkyne, the protonation and hydrogen migration of five-component ring containing silver. In the second process, the formation of C2-C4 bond is the decisive step of the reaction, and the required activation free energy barrier (G (?) It is 10.2 kcal mol. The catalyst Ag_2CO_3 plays a dual role in the formation of isonitrile radical: it is used as an initiator for the extraction of protons on isonitrile C 偽 atom and the formation of isonitrile radical. Isonitrile and solvent 1,4-dioxane were used as proton donors to realize silver pentagonal cycloprotonization at the same time, and the corresponding free radical species were obtained. 1, 4-dioxane can be used as free radical transporter to initiate the formation of isonitrile radical. In addition, 1, 4-dioxane as promoter and proton donor / receptor can effectively reduce the activation energy barrier during hydrogen migration and increase the reaction activity. This finding provides a new idea for the catalytic reaction of isonitrile or alkynes catalyzed by transition metal silver salt, and provides a new idea for the optimization of catalytic reaction conditions of silver salt. 2. The mechanism of hydroazide synthesis of alkenyl azide catalyzed by water and silver carbonate was investigated by DFT. It was found that the reaction was mainly through the coordination of Ag_2CO_3 with substrate TMS-N_3 to promote the reaction of water with TMS-N_3 to form HN_3, water to assist Ag_2CO_3 in the protonation of terminal alkynes to form silver alkynes. The selective addition of HN_3 with acetylene silver and the protonation of AgHCO_3 to terminal carbon atoms formed alkenyl azide products. In the third step, the formation of C 鈮，
本文編號(hào)：2508278
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