辅酶NADH模型物还原活化烯烃反应机理研究

2001 年第21卷有机化学\ul.21. 2001第11期,898 ~ 903Chiner Joumal of Onpnic CarmistryNo. 1.898 ~ 903●研究成果报告.辅酶NADH模型物还原活化烯烃反应机理研究刘有成"a.b李劲“("中国科学技术大学化学系合 肥230026)06 A(*兰州大学应用有机化学国家重点实验室兰州 730000)摘要对本课题组近年来研究的辅酶NADH模型物还原活化烯烃的反应机理进行了综述。刘于铺酶模型物还原2-澳小苯其亚乙基内二腈类化合物的反应.依赖辅酶模型物和底物的结构，反应可以按一步的负氢转移机理或按电了转移机理进行。用手性辅酶模型物进行这一反应.叮得到其有中等光学活性的环丙烷衔生物。实验结果表明辅酶模型物BNAH与1.1二举基-2.2-二硝基乙烯的反应的过渡态具有部分双自由基和部分共价键形成的特征,为Pross Shaik“曲线交叉模型"所预测的“中间机理"提供了直接的证据。BNAH与9-业芴基丙-二腈的反应经历电子转移和负电荷在9-位碳上的碳负离子中间体,动力学同位素效应为2.6。关键词辅酶 NADH还原,反应机理,负氢转移,单电子转移.曲线交叉模型Study on the Mechanism of Reduction of Activated Ethyleneswith Coenzyme NADH ModelsLIU You-Cheng"aib，L Jing"(° Departmert of Chenaitry. Uniresity of Srience and Technology of China, 230026 Hegfei)(“National Laboratory of Aplied Organir Chemstry. Lanzhuu Unirerity ，730000 Imnzhou)Abstract The reduction of a series of 2-bromo- 1-(X-pheny!)ethylidene malonic derivatives with Coenzyme NADHmodels has been investigated. Depending on the structure of substrates and that of the model, hydride transfer mechanismand electron transfer mechanism could be diferentated. Thus， the reaction of 4-benzyl-I ，4-dihydronicotinamide( BNAH) with 2-brurno-l-phenyethylidenemalononitrile produced 2-penylcyclopropane-l, l-dinitrile through hydnidetransfer mechanism, while the reaction of 10-methyl-9, 1-dihydracridine with 2-bromo-1-phenylethylidenemalonontilegave I-phenyletbylidenenalontrle through electon transfer, debromination and hydrogen abstaction mechanism. Sudics on substiuent efet and kinetic isotope ef suppor the eunclusion. Using (5S)-benzy)-3-( polyul6iny)-1,4,dihydropyridine as a chiral NADH model, the synthesis of phenylcyclopropane derivatives with moderate optical activityhas been achieved. Based on the evidence of kinetic isotope ef.et and tapping with oxygen, the reduction of 1,1dipheny-2.2-dinitoethylene with BNAH has been shown to proceed through a transition state of partial diradical and par-tial covalent bonding character. This was caused by sterie hindrance of the subtuent phenyl and mitro groups as demon-strated by X-ray srstalogaphic analysis of the subtrate molecule. This provides eridence for the existenve of an' *inter-mediate mechanism”between polar mechanism and electron transter mechanism acording to Pros Shaik“Curve CrossingModel" . The reduction of 9-flurenylideneralonnitrile with BNAH proceeded through electron lransfer and the intermne-diacy of a carbanion with negative charge on C-9 of fluorenyl nucleus and showed a kinetie H/D istope efet of2.6.Further researh work is in progress.Key words NADH model, electron lransfer, curve crossing model■Received 2001-07-13; Aceped 2001-08-30.国家自然科学基金(Nos.29392201, 29672031, 29832040)资 助项目。.第11期刘有成等:辅酶NADH模型物还原活化烯烃反应机理研究1前言1,4-”“氢烟酰胺腺嘌呤二核背酸(NADH)是--应则是按电子转移、脱溴、夺氢机理进行的(Scheme个典型的辅酶,它在生物氧化-还原反应中起着重1)。要的作用。有关NADH如何转移形式上的一一个负氢给反应底物的问题-直是令人感兴趣的课题,大部Hy