THERMAL REACTIONS OF ALKYL N-CARBOMETHOXYSULFAMATE ESTERS
THERMAL REACTIONS OF ALKYL N-CARBOMETHOXYSULFAMATE ESTERS
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DOI：
10.1021/jo00941a006
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发表时间：
1973-01-01
影响因子：
3.6
通讯作者：
TAYLOR, EA
中科院分区：
文献类型：
--
作者：
BURGESS, EM;PENTON, HR;TAYLOR, EA
合成了三乙基氢氧化铵、内盐、甲酯，并与广谱醇反应生成烷基a -碳甲氧基氨基磺酸酯。叔醇和仲醇易转化为烯烃，伯醇易转化为氨基甲酸乙酯，证明了氨基甲酸酯作为离去基在热解脱水反应中的应用范围和合成用途。从立体化学上看，该反应是由二苯基乙基/碳甲氧基磺胺形成的仅为原二苯乙烯的顺式立体特异性消除反应。从相应的红细胞化合物中摄取三乙胺盐和纯氘-írans-stilbene。用分光光度法测定了二苯基乙醇体系的一级速率常数（fe5= 2.66 × 10~ 6），并观察到一个小的/3-氘同位素效应(对赤二酚（red thro) = 1.05，对三酚(threo) = 1.08）。计算了热解的活化参数，其值为22.4 keal/mol,*= 21.7 keal/mol, AG*= 22.8 keal/mol, AS*= -3.3 eu。这些动力学和立体化学结果与离子对的初始限速形成相一致，随后快速顺式质子转移到离开的阴离子上，其速率大于红离子和三氧离子对的相互转换。通过一阶热裂解Ei分解衍生酯的醇脱水已成为一种有价值的方法在组合的实际合成有机反应。与溶剂溶解消除相比，在这种消除的过渡状态中，顺式氢的几何约束和a-碳碳离子特征的缺失（因此骨架重排）提供了一个可预测的，因此在定向合成序列中具有战略意义的有用步骤。存在一种Ei机制定时的变体
(Carboxysulfamoyl) triethylammonium hydroxide, inner salt, methyl ester was synthesized and shown to react with a broad spectrum of alcohols resulting in alkyl A-carbomethoxysulfamate esters. The scope and synthetic usefulness of the sulfamate ester function as a leaving group in thermolytic dehydration reactions was demon-strated by the facile conversionof tertiary and secondary alcohols to olefins and primary alcohols to urethanes. Stereochemicallv the reaction was established as a cis-stereospecific elimination by theformation of onlyprotioirans-stilbene from iZireo-2-deuterio-l, 2-diphenylethyk/V-carbomethoxysulfam. ate triethylammonium salt and only-deuterio-írans-stilbene from the corresponding erythro compound. The first-order rate constants for the diphenylethanol system were determined spectrophotometrically (fe5= 2.66 X 10~ 6) and a small/3-deuterium isotope effect was observed AhAd= 1.05 for erythro and 1.08 for threo compound). Activation parameters were calculated for the thermolysis with values= 22.4 keal/mol,*= 21.7 keal/mol, AG*= 22.8 keal/mol, AS*=—3.3 eu. These kinetic and stereochemical results are consistent with an initial rate-limiting formation of an ion pair followed by a fast cis ß proton transfer to the departing anion at a rate greater than the interconver-sion of erythro-and threo ion pairs.The dehydration of alcohols via a first-order thermo-lytic Ei decomposition of a derived ester has been a valuable method in the portfolio of practiced synthetic organic reactions. When compared to solvolytic elimination, the cis-ß hydrogen geometrical constraint and the absence of a-carbon carboniumion character (and thus skeletal rearrangements) in the transition state of such eliminations provide a predictable and therefore strategically useful step in a directed synthetic sequence. A variant of the Ei mechanism timing exists