REACTIONS OF ALKYLMERCURIALS WITH HETEROATOM-CENTERED ACCEPTOR RADICALS
REACTIONS OF ALKYLMERCURIALS WITH HETEROATOM-CENTERED ACCEPTOR RADICALS
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DOI：
10.1021/ja00219a030
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发表时间：
1988-05-25
影响因子：
15
通讯作者：
KHANNA, RK
中科院分区：
文献类型：
--
作者：
RUSSELL, GA;NGOVIWATCHAI, P;KHANNA, RK
从R= 0 -丁基到R= s -烷基再到R= n-丁基，烷基卤化汞对ph “、PhSe”或I“的相对反应活性急剧下降，表明R”是在这些自由基攻击RHgCl的速率决定步骤中形成的。由此形成的烷基自由基将进入链式反应，其中杂原子中心自由基（a '）从RS-SR、ArSe-SeAr、ArTe-TeAr、PhSe-S02Ar、Cl-S02Ph等底物中再生；ZCH= CHA (A= Cl， I, SPh, so2ph)；或PhO^ CHA （A= I, SPh, so2ph）。/3-苯乙烯基（PhCH= CHA, Ph2C= CHA）和/3-苯乙基（PhC^ CA）体系，A= I, Br， so2ph2也与汞（II）盐与配体ph， PhSe， PhS02或（EtO） 2PO发生链式反应。报道了一系列试剂对Z- bu *和PhCH= CHA、Ph2C= CHA和PhO^= CA对c-C6Hu”的相对反应活性，以及对Ph、Cl、Br、I、so2ph、SPh、Bu3Sn基团中Z和a的1,2 -二取代乙烯（ZCH== CHA）的Z- bu”攻击的区域选择性。（£）和(Z)-PhCH= CHI或Me02CCH= CHI与Z- bu”或c-C6Hu*的反应以区域选择性和立体特异性（保留）的方式发生。（£）和(Z)-C1CH= CHC1的反应以非立体定向的方式发生，其中£/Z的生成物比随着攻击自由基的增加而增加。(Z)-Me02CCH= CHCl对£/Z产物比率也有类似的影响。烷基汞化合物（RHgX, R2Hg）被认为会受到卤素原子对汞的攻击，形成烷基自由基。烷基汞化合物与卤素分子的3-5次反应通过对汞的均溶反应和对碳的亲电反应生成烷基卤化物，尽管在许多情况下可以选择有利于离子或均溶过程的条件。烷基汞和邻近的二卤化物（如C2C16）之间的反应通过自由基链过程导致脱卤，其中卤素原子被R*抽离，然后卤素原子被1 /3消去，通过攻击汞再生R"。6·7
The relative reactivities of alkylmercury halides towardPhS", PhSe", or I" decrease drastically from R= zerz-butyl to R= sec-alkyl to R= n-butyl, indicative that R" is formed in the rate-determining step in the attackof these radicals upon RHgCl. The alkyl radicals thus formed will enter into chain reactions in which a heteroatom-centered radical (A") is regenerated from substrates such as RS-SR, ArSe-SeAr, ArTe-TeAr, PhSe-S02Ar, Cl-S02Ph; ZCH= CHA (A= Cl, I, SPh, S02Ph); or PhO^ CHA (A= I, SPh, S02Ph)./3-Styrenyl (PhCH= CHA, Ph2C= CHA) and/3-phenethynyl (PhC^ CA) systems with A= I, Br, S02Phalso enter into chain reactions with mercury (II) salts with the ligands PhS, PhSe, PhS02, or (EtO) 2PO. The relative reactivities of a series of reagents toward Z-Bu* and of PhCH= CHA, Ph2C= CHA, and PhO^= CA toward c-C6Hu" are reported as well as the regioselectivity of Z-Bu" attack observed for 1, 2-disubstituted ethylenes (ZCH== CHA) with Z and A from the group Ph, Cl, Br, I, S02Ph, SPh, Bu3Sn. Reactions of (£)-and (Z)-PhCH= CHI or Me02CCH= CHI with Z-Bu" or c-C6Hu* occurred in a regioselective and stereospecific (retention) manner. Reactions of (£)-and (Z)-C1CH= CHC1 occurred in a nonstereospecific manner in which the£/Z product ratio increased with the bulk of the attacking radical. A similar effect on the£/Z product ratios was observed for (Z)-Me02CCH= CHCl.Alkylmercurials (RHgX, R2Hg) are recognized to undergo attack at mercury by halogen atoms to form alkyl radicals. 3-5 Reactions of alkylmercurials with halogen molecules yield the alkyl halides by both homolytic attack at mercury and electrophilic attack at carbonalthough in many cases it is possible to select conditions which will favor either the ionic or homolytic process. 3 The reactions between alkylmercurials and vicinal dihalides (eg, C2C16) leads to dehalogenation by a free-radical chain process involving halogen atom abstraction by R* followed by a/3-elim-ination of a halogen atom which regenerates R" by attack upon the mercurial. 6· 7