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  • 學位論文

Corey-Chaykovsky 試劑與鄰羥二苯甲酮衍生物反應之取代基效應的研究

The substituent effect on the reaction of 2-hydroxybenzophenones with Corey-Chaykovsky reagents

指導教授 : 廖俊臣 謝興邦

摘要


本論文研究Corey-Chaykovsky試劑與具有不同取代基的鄰羥二苯甲酮之新穎反應。第一部分探討取代基之影響,第二部分研究各產物之反應路徑。   第一部分:不同於以往應用Corey-Chaykovsky試劑於環氧化反應時的製備方法,使用正丁基鋰為鹼、以無水四氫呋喃為溶劑所製備出之Corey-Chaykovsky試劑具有不同反應性,故導致新穎反應的發生。各種鄰羥二苯甲酮大部分以不同取代之苯甲醛為起始物經由Grignard反應、重鉻酸吡啶氧化、去保護基等步驟合成。接著與Corey-Chaykovsky試劑1進行反應可得三類產物,其中具有推電子基或部分較弱之拉電子基的鄰羥二苯甲酮可得第Ⅰ類重排產物及合環產物,接著置於酸性環境下形成高產率之2-苯基苯并呋喃及3-苯基苯并呋喃;另外具有硝基於羰基對位取代之鄰羥二苯甲酮則會形成第Ⅱ類重排產物,產率隨芳香環之電子密度高低而減增。 第二部分:依據各產物推測具有四種反應路徑,其中形成合環產物之途徑有二,推測均是先形成具有環氧基之中間體122。故以鄰羥二苯甲酮為起始物,分別以三級丁基二甲基矽基氯及對位甲氧基溴甲苯保護羥基接著以間氯過氧苯甲酸進行環氧化反應可得化合物127a~b,再與4當量之Corey-Chaykovsky試劑1在無水四氫呋喃中反應而得到合環產物106m、126m之混合物,因此證實3-苯基苯并呋喃確實經由環氧丙烷中間體而形成,且反應中鋰離子與CCR1之存在為必要條件。

並列摘要


This thesis aims at the studies on the novel rearrangement of 2-hydroxybenzophenone on reaction with Corey-Chaykovsky reagent. The first part is concerned with the effects of substituents on 2-hydroxybenzophenone and the second part describes the plausible mechanism for the observed products.   When n-butyllithium (n-BuLi) was used as base in tetrahydrofuran (THF) to generate Corey-Chaykovsky reagent, it was found that the reagent had totally different reactivity towards the substrate in comparison to Corey-Chaykovsky reagent prepared using sodium hydride (NaH) as base in dimethylsulfide (DMSO). Initially, various substituted 2-hydroxybenzophenones were prepared from Grignard reactions of benzaldehyde derivatives followed by sequential oxidation and deprotection. These substrates were next subjected to Corey-Chaykovsky reaction to afford three kinds of products, two of which are one-carbon homologated products with different regioselectivity called the rearranged product Ⅰ andⅡ, and the third being cyclized product. The rearranged products Ⅰ were obtained for 2-hydroxybenzophenones with electron-donating substitutions or weakly electron-withdrawing substitutions on the aryl ring and were accompanied by the cyclized products. A strongly electron-withdrawing substituent like nitro group at the position 4’ led to the rearranged productⅡ. Four pathways are suggested for furnishing the observed products in which two are used to interpret formation of the cyclized compounds. The epoxide compound (122) is considered to be the intermediate in these two paths. To confirm the proposed mechanisms, protected epoxide compounds were obtained by epoxidation of t-butyldimethylsilyl chloride (TBDMSCl) and p-methoxybenzyl bromide (PMBBr) protected 2-hydroxybenzophenone. These compounds were subjected to Corey-Chaykovsky reaction condition to generate the cyclized products. Consequently, it is now proved that the epoxide intermediate exits in the reaction and the pathway might be correct for the formation of the cyclized products.

參考文獻


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