輔酶NADH模型物還原活化烯烴反應機理研究

2001 年第21卷有機化學(xué)\ul.21. 2001第11期,898 ~ 903Chiner Joumal of Onpnic CarmistryNo. 1.898 ~ 903●研究成果報告.輔酶NADH模型物還原活化烯烴反應機理研究劉有成"a.b李勁“("中國科學(xué)技術(shù)大學(xué)化學(xué)系合 肥230026)06 A(*蘭州大學(xué)應用有機化學(xué)國家重點(diǎn)實(shí)驗室蘭州 730000)摘要對本課題組近年來(lái)研究的輔酶NADH模型物還原活化烯烴的反應機理進(jìn)行了綜述。劉于鋪酶模型物還原2-澳小苯其亞乙基內二腈類(lèi)化合物的反應.依賴(lài)輔酶模型物和底物的結構，反應可以按一步的負氫轉移機理或按電了轉移機理進(jìn)行。用手性輔酶模型物進(jìn)行這一反應.叮得到其有中等光學(xué)活性的環(huán)丙烷銜生物。實(shí)驗結果表明輔酶模型物BNAH與1.1二舉基-2.2-二硝基乙烯的反應的過(guò)渡態(tài)具有部分雙自由基和部分共價(jià)鍵形成的特征,為Pross Shaik“曲線(xiàn)交叉模型"所預測的“中間機理"提供了直接的證據。BNAH與9-業(yè)芴基丙-二腈的反應經(jīng)歷電子轉移和負電荷在9-位碳上的碳負離子中間體,動(dòng)力學(xué)同位素效應為2.6。關(guān)鍵詞輔酶 NADH還原,反應機理,負氫轉移,單電子轉移.曲線(xiàn)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.國家自然科學(xué)基金(Nos.29392201, 29672031, 29832040)資 助項目。.第11期劉有成等:輔酶NADH模型物還原活化烯烴反應機理研究1前言1,4-”“氫煙酰胺腺嘌呤二核背酸(NADH)是--應則是按電子轉移、脫溴、奪氫機理進(jìn)行的(Scheme個(gè)典型的輔酶,它在生物氧化-還原反應中起著(zhù)重1)。要的作用。有關(guān)NADH如何轉移形式上的一一個(gè)負氫給反應底物的問(wèn)題-直是令人感興趣的課題,大部Hy