Lead-Tetraacetate Oxidations of Stereoisomeric 2-Methyl-3-Phenylbutyric Acids.
Lead-Tetraacetate Oxidations of Stereoisomeric 2-Methyl-3-Phenylbutyric Acids.
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立体异构 2-甲基-3-苯基丁酸的四乙酸铅氧化。
DOI：
10.1021/jo00916a006
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发表时间：
1974
期刊：
影响因子：
--
通讯作者：
J. Traynham
中科院分区：
文献类型：
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作者：
Sister Alice Theine;J. Traynham
先前对立体异构的叔丁基环己烷羧酸的研究已经证明，通过卤代脱羧由环己基衍生的产物和通过用四乙酸铅氧化脱羧由阳离子衍生的产物与起始酸的构型无关。从异构体异丙基-2-羧酸和异丙基-2-羧酸的氧化脱羧得到了类似的结果。本研究关注的是可能产生取代的2-苯乙基阳离子的立体异构酸。同分异构体2-甲基-3-苯基丁酸的卤代脱羧产生相同的1：1.U赤苏型2-氯-3-苯基丁烷。这些酸氧化脱羧的取代和消除产物均显示相同的分布（U.6：1 Z：E 2-苯基-2-丁烯和1.7：1邻位：苏位1-甲基-2-苯基-1-丙基乙酸酯）。显然，一个共同的自由基正在产生，它被进一步氧化成一个单一的阳离子物种。这一个阳离子然后产生取代和消除产物，而与起始酸的构型无关。自由基和阳离子中间体形成了不同比例的反式：苏式取代产物，这是由于这两个过程中涉及的空间和其他能量因素的不同组合。在乙酸溶液中的溶剂分解和脱氨基反应以及与四乙酸铅的脱羧反应都从1-甲基-2-苯基-1-丙基反应物产生乙酸酯取代产物。甲苯磺酸酯或对溴苯磺酸酯的溶剂分解和脱氨基反应得到
Previous studies with stereoisomeric it-£-butylcyclohexanecarboxylic acids have demonstrated that the products derived from the cyclohexyl radical by halodecarboxylatlon and those derived from the cation by oxidative decarboxylation with lead tetraacetate are indepen dent of the configuration of the starting acids. Similar results have been obtained from the oxidative decarboxylation of the isomeric bornane-2-carboxylic acids and norbornane-2-carboxylic acids. The present study has been concerned with stereoisomeric acids from which substituted 2-phenylethyl cations might be generated. Halodecarboxylations of the isomeric 2-methyl-3-phenylbutyric acids produce the same 1:1.U erythrozthreo ratio of 2-chloro-3-phenylbutanes. Both the substitution and elimination products from oxidative decarboxylation of these same acids show identical distributions (U.6 :l Z:E 2-phenyl-2-butenes and 1.7:1 erythro:threo 1-methyl-2-pheny1-1propyl acetates). Apparently a common radical is being generated which is further oxidized to a single cationic species. This one cation then gives rise to both substitution and elimination products Independently of the configuration of the starting acids. Different ratios of erythro:threo substitution products are formed from the radical and cationic intermediates, due to differing combinations of steric and other energy factors involved in the two processes. Solvolytic and deamination reactions in acetic acid solutions and decarboxylation reactions with lead tetraacetate all yield acetate substitution products from 1-methyl-2-phenyl-1-propyl reactants. Solvolysis of the tosylate or brosylate and the deamination reaction give