2,5—二叔丁基对二甲氧基苯的去叔丁基反应的研究

２，５－二叔丁基对二甲氧基苯（１）在ＣＦ３ＣＯ２Ｈ，ｎ－Ｃ３Ｆ７ＣＯ２Ｈ或ＡｌＣｌ３－ＣＨ２Ｃｌ２体系中易发生去叔丁基化反应，而强质子酸ＨＩ（ａｑ），ＨＢＦ或ＣＣｌ３ＣＯ２Ｈ中不发生此反应。在前一类体系中，都可在反应过程中观察到较强的阳离子基１＾＋的ＥＰＲ信号，而在后一类体系中则无此信号。动力学测定表明，受物１与三氟乙酸的反应表现为三级动力学，其中１为二级，ＣＦ３ＣＯ２Ｈ为一级。这些结果揭示了去叔     

（四甲基二硅撑）双（3－三甲硅基环戊二烯基）－四羰基二铁的反应性

标题化合物（Ｍｅ_２ＳｉＳｉＭｅ_２）［η￣５－（３－Ｍｅ_３ＳｉＣ_５Ｈ_３）Ｆｅ（ＣＯ）_２］_２／（μ－ＣＯ）_２（Ａ）分子中的Ｆｅ－Ｆｅ键被钠汞齐还原断裂，生成相应的双铁负离子，分别与ＭｅＣＯＣｌ、ＰｈＣＯＣｌ、ＰｈＣＨ_２Ｃｌ、ＣｌＣＨ_２ＣＯＯＣ_２Ｈ_５和Ｐｈ_３ＳｎＣｌ进行亲核取代反应，生成在铁原子上引入相应取代基的产物（Ｍｅ_２ＳｉＳｉＭｅ_２）［η￣５－（３－Ｍｅ_３ＳｉＣ_５Ｈ_３）Ｆｅ（ＣＯ）_２Ｒ］_２（Ｒ：ＭｅＣＯ（１），ＰｈＣＯ（２），ＰｈＣＨ_２（３），ＣＨ_２ＣＯＯＣ_２Ｈ_５（４），Ｐｈ_３Ｓｎ（５），Ｉ（６））。Ａ在氯仿中与碘反应，得到Ｆｅ－Ｆｅ断裂的双铁碘化物，但在苯中与过量碘反应，则得到Ｆｅ－Ｉ－Ｆｅ桥联的离子型化合物（Ｍｅ_２ＳｉＳｉＭｅ_２）［η￣５－（３－Ｍｅ_３ＳｉＣ_５Ｈ_３）Ｆｅ（ＣＯ）_２］_２Ｉ·Ｉ（７）。化合物６的晶体和分子结构经Ｘ射线衍射测定，６属单斜晶系，Ｐ２１／ｃ空间群，ａ＝１．７２１７（４）ｎｍ，ｂ＝０．７７５３（２）ｎｍ，Ｃ＝１．３６２９（７）ｎｍ，β＝１０３．８０（３）°，Ｖ＝１．７６７（２）ｎｍ３，Ｚ＝４，Ｄｃ＝１．６２９９·ｃｍ－１，最终偏差因子Ｒ＝０．０５４。     

环状配合物Me_2Si［η~5－C_5H_4Fe（CO）_2］_2SnR_2的合

通过ＳｎＣｌ_２对化合物Ｍｅ_２Ｓｉ［η~５－Ｃ_５Ｈ_４Ｆｅ（ＣＯ）］_２（μ－ＣＯ）_２（Ⅰ）中Ｆｅ－Ｆｅ键的插入反应以及Ⅰ被Ｎａ－Ｈｇ齐还原所生成的相应双铁负离子｛Ｍｅ_２Ｓｉ［η~５－Ｃ_５Ｈ_４Ｆｅ（ＣＯ）_２］_２｝~（２－）与ＳｎＲ_２Ｃｌ_２（Ｒ＝Ｍｅ，Ｐｈ）的亲核反应，合成了环状化合物Ｍｅ_２Ｓｉ［η~５－Ｃ_５Ｈ_４Ｆｅ（ＣＯ）_２］_２ＳｎＲ_２［Ｒ＝Ｃｌ（１），Ｍｅ（２），Ｐｈ（３）］。以元素分析、ＩＲ和~１ＨＮＭＲ谱表征了它们的结构，并用Ｘ射线衍射测定了配合物３的晶体结构。３为单斜晶系，空间群Ｐ２_１／ｎ，ａ＝１．０３８４（３）ｎｍ，ｂ＝１．６３８４（１）ｎｍ，ｃ＝１．５７６２（５）ｎｍ，β＝９７．９３（２）°，Ｖ＝２．６５６（２）ｎｍ~３，Ｚ＝４，Ｄｘ＝１．７１ｇ／ｍＬ。     

CS_2在Cu－S键中插入产物（Ph_3P）_2Cu（S_2CSR）与溶剂反应的

ＣＳ_２在Ｃｕ－Ｓ键中插入产物（Ｐｈ_３Ｐ）_２Ｃｕ（Ｓ_２ＣＳＰｈ）与ＣＨ_２Ｃｌ_２－Ｃ_２Ｈ_５ＯＨ混合溶剂反应，获得单核铜配合物（Ｐｈ_３Ｐ）_２Ｃｕ（Ｓ_２ＣＯＯＣ_２Ｈ_５）和双核铜配合物（Ｐｈ_３Ｐ）_３Ｃｕ_２Ｃｌ_２等化合物晶体，用Ｘ－射线单晶衍射法测定前者的晶体结构。晶体的化学式为Ｃ_（３９）Ｈ_（３５）ＣｕＯＰ_２Ｓ_２，分子量为７０９．３，空间群Ｐ２１／ｎ，ａ＝９．３２９（６），ｂ＝１８．６６４（１１），ｃ＝２０，３４１（１３），β＝９５．５９（５）°，Ｖ＝３５２５（４）~３，Ｄ_ｃ＝１．３３７ｇ／ｃｍ~３，Ｚ＝４，Ｆ（０００）＝１４９２，μ＝０．８５２ｍｍ~（－１），Ｒ＝０．０４５。     

含固氮酶钼微环境结构单元O_3MoS_3的Mo－S，Mo－Fe－S化合物的研究

研究了含固氮酶钼微环境Ｏ_３ＭｏＳ_３结构单元四个系列化合物［Ｍｏ（Ｓ，Ｏ－Ｃ_６Ｈ_４－１，２］~－（Ｍ）［Ｍｏ_２（ＣＯ）_３（Ｓ，Ｏ－Ｃ_６Ｈ_４－１，２）_３］~（２－）（Ｄ），［Ｍｏ_３（ＣＯ）_７（Ｓ，Ｏ－Ｃ_６Ｈ_４－１，２）_３］~（２－）（Ｔ），和［Ｍｏ_２Ｆｅ（ＣＯ）_４（Ｓ，Ｏ－Ｃ_６Ｈ_４－１，２）_３Ｃｌ_２］~（２－）（Ｔ_ｆ）的合成化学与结构化学，并通过Ｘ－射线光电子能谱，红外光谱和电化学环伏安研究，深入探讨了它们的混合价，电子迁移和电化学行为，也讨论了有趣的Ｏ_３ＭｏＳ_３结构单元。     

（四甲基二硅撑）二（3－三甲硅基环戊二烯基）四羰基二铁及其相关化合物的合成及结构

１，２－二（三甲硅基环戊二烯基）四甲基二硅烷与Ｆｅ（ＣＯ）_５在二甲苯中于１０５～１１０℃反应除分离到少量标题化合物（Ｍｅ_２ＳｉＳｉＭｅ_２）［η－（３－Ｍｅ_３ＳｉＣ_５Ｈ_３Ｆｅ（ＣＯ）］_２（μ－ＣＯ）_２（５）外，主要是生成了脱Ｍｅ_３Ｓｉ基的产物（Ｍｅ_２ＳｉＳｉＭｅ_２）［η－Ｃ_５Ｈ_４Ｆｅ（ＣＯ）］_２（μ－ＣＯ）_２（１）及１的热重排异构体［Ｍｅ_２ＳｉＣ５Ｈ４－Ｆｅ（ＣＯ）_２］_２（２）．将５的二甲苯溶液加热回流１８ｈ，则转化为其异构体［Ｍｅ_２Ｓｉ（Ｍｅ_３ＳｉＣ_５Ｈ_３）Ｆｅ（ＣＯ）_２］_２（６）．脱硅基发生在由相应反应物制备５的过程中。且脱硅基是与反应物中（Ｍｅ_２ＳｉＳｉＭｅ_２）桥的存在有关．５的晶体结构经Ｘ射线衍射测定属单斜晶系，Ｐ２_１／ｍ空间群，晶体学数据：ａ＝０．６７８０（１）ｎｍ，ｂ＝２．２３０３（９）ｎｍ，ｃ＝０．９９８８（１）ｎｎ，；β＝９８．９６（１）°，Ｖ＝１．４９６０ｎｍ~３．Ｚ＝２，Ｄ_ｃ＝１．３６ｇ／ｃｍ~３．     

一氟二氯代甲烷热解离动力学的理论研究

利用从头算和ＲＲＫＭ理论研究了一氟二氯代甲烷热解离动力学，并得到了一套热力学和动力学参数。研究了三种不同的解离通道：（１）ＨＣｌ＋ＣＦＣｌ_２，（２）Ｃｌ＋ＣＨＦＣｌ，（３）ＨＦ＋ＣＣｌ_２，它们的活化能分别为：２４３．３、２５８．９、３０９．８ｋＪ／ｍｏｌ。研究结果表明，氯化氢消除反应和碳氯键简单断键反应是两个主要的并且是竞争的通道，三个反应通道的高压速率常数分别为ｋ_１＝８．７４×１０~（１４）ｅｘｐ（－２９１６３Ｔ）_ｓ~（－１），ｋ_２＝７．０９×１０~（１５）ｅｘｐ（－３１１２１／Ｔ）_ｓ~（－１），Ｒ_３＝３．８７×１０~（１１）ｅｘｐ（－３７０３９／Ｔ）_ｓ~（－１），它们都具有明显的温度和压力依赖关系。     

与甲醇合成铜基催化剂研究有关的ZnO和ZnO－Al_2O_3体系的ESR及XPS表征

本文用ＥＳＲ谱和ＸＰＳ谱对这类催化剂作了表征研究。结果表明，在经Ａｌ￣（３＋）掺杂的ＺｎＯ－Ａｌ_２Ｏ_３体系上，观测到ｇ＝１．９６０６±０．０００２，△Ｈ_（ｐｐ）＝（２．８±０．１）×１０￣（－４）Ｔ的顺磁信号，该信号强度（以自旋数／克表示）随ＺｎＯ中Ａｌ_２Ｏ_３掺杂量增加而增长；当Ａｌ／Ｚｎ达２／１００（原子比）时，逐渐趋于平稳。相关体系的ＥＳＲ和ＸＡＥＳ比较研究结果排除了该顺磁信号系产生于顺磁氧物种（诸如，Ｏ_２－、Ｏ－或Ｏ_３－）或Ｚｎ＋的可能性，而有利于关于三价金属离子（ＡＬ￣（３＋））掺杂在ＺｎＯ晶格中诱导生成正一价缺位的推断。这类Ｓｈｏｔｔｋｙ缺位在催化剂表面富集，有利于表面Ｃｕ￣＋物种的稳定，从而促进了ＣＯ加氢活性的提高。     

μ－氧代双锰（Ⅲ）卟啉氧化反应及取代基效应研究

用紫外－可见光谱对氧化剂ＰｈＩＯ、Ｈ_２Ｏ_２和空气对μ－氧代双四苯基卟吩合锰（［ＴＰＰ·Ｍｎ（Ⅲ）］_２Ｏ）的氧化过程进行监测，揭示了［ＴＰＰＭｎ（Ⅲ）］_２Ｏ在不同氧化剂作用下具有不同的反应过程。研究了８种取代μ－氧双四苯基卟吩合锰｛［ＴＸＰＰＭｎ（Ⅲ）］_２Ｏ，Ｘ＝ｐ－（ｉ－Ｐｒ），ｐ－ＣＨ_３，ｐ－Ｃｌ，ｐ－Ｆ，ｐ－ＯＣＨ_３，Ｈ，ｍ－Ｃｌ，ｏ－Ｃｌ｝与Ｈ_２Ｏ_２反应中的取代基效应和溶剂效应。结果表明：上述反应为卟啉环上的吸电子基所促进；且反应速率随着反应溶剂的亲核性能的增加而增加。     

含2，4－二硫代乙内酰脲分子片卡宾铁羰基簇合物的合成和结构

Ｆｅ_３（ＣＯ）_（１２）与５个２，４－二硫代乙内酰脲ＳＣＮＨＣ（Ｒ_１）（Ｒ_２）Ｃ（Ｓ）ＮＨ反应制得通式为Ｆｅ_３（ＣＯ）_８（ｕ３－Ｓ）_２（Ｌ）含卡宾配体的５个新铁羰基联合物（１～５），对其进行了元素分析、ＩＲ、~１ＨＮＭＲ和ＭＳ表征，并用Ｘ射线衍射法测定了簇合物３的晶体和分子结构，表明２，４－二硫代乙内酰脲分子片配位基：ＣＮＨＣ（ＣＨ_３）_２Ｃ（Ｓ）ＮＨ的卡宾碳具有ｓｐ~２成键特征，其Ｃ卡宾－Ｆｅ键长０．１８９８ｎｍ，３的分子几何构型维持母体物Ｆｅ_３（ＣＯ）_９（ｕ_３－Ｓ）_２的形状，其中卡宾取代了四方锥分子骨架基底平面Ｆｅ（１）Ｓ（１）Ｆｅ（３）Ｓ（２）的Ｆｅ（１）原子上轴向位置的一个端羰ＣＯ。     

ONIOM(DFT:MM) study of 2-hydroxyethylphosphonate dioxygenase: what determines the destinies of different substrates?

Why can enzymes provide different products from only slightly different substrates? While the reaction of 2-hydroxyethylphosphonate (2-HEP) catalyzed by 2-hydroxyethylphosphonate dioxygenase (HEPD) yields hydroxymethylphosphonate and formic acid, the HEPD-catalyzed reaction of 1-HEP gives acetylphosphate. ONIOM(DFT:MM) was used to uncover the distinct reaction mechanisms for the different substrates. Calculations show that, in both reactions, similar radical intermediates are generated by the same process. After the formation of common radical intermediates, proton-coupled electron transfer (PCET) operates in the 1-HEP reaction, whereas in the 2-HEP reaction, it cannot occur and an alternative pathway sets in. Thus, the PCET plays a critical role in defining the fates of the substrates.     

Radical additions of xenon difluoride to cis- and trans-1-phenylpropenes: comparison with trichloramine and iodobenzene dichloride

We would like to report data which support a free radical pathway for reaction of xenon difluoride (XeF₂) with alkenes in organic solvent. Radical intermediates have been proposed for reaction of XeF₂ to double bonds. For example, a radical pathway was suggested for the gas phase reaction of XeF₂ to ethylene and propene [1]. Zupan speculated on a radical cation pathway for the acid catalyzed reaction of XeF₂ with alkenes but gave no experimental evidence for this mechanism [2,3]. Radical cation intermediates were demonstrated for the reaction of XeF₂ to aromatics by Filler [4]. Acid catalyzed ionic reactions to unsaturated hydrocarbons have been reviewed [5].Zupan and Pollak have shown that alkenes do not react in aprotic solvent with XeF₂ at low concentrations of alkene unless acid catalyst is present [3]. However, we observed that illumination of a dilute solution of $\text{cis-}$ or $\text{trans}$-1-phenylpropenes (I) or (II) in methylene chloride at 0° with a 270 watt sunlamp produced IIIa and IIIb in less then two hours (Table). Furthermore, at high concentration of (I) and (II), a spontaneous reaction occurred in the dark between XeF₂ and these styrenes. The reaction conditions for both of these reactions imply a radical mechanism — the latter a molecule-induced pathway.     

New synthetic route to α-alkylacrylonitriles and a study of their homopolymerization and copolymerization reactions

Aliphatic aldehydes have been condensed with cyanoacetic acid and the resulting olefin intermediates hydrogenated and then submitted to a Mannich-type reaction to produce α-alkylacrylonitriles with the alkyl groups ranging from C₁ to C₁₂. It was not necessary to isolate the intermediates when the reactions were carried out in acetonitrile solutions. The α-alkylacrylonitriles with C₇ or higher alkyl groups in the chains would polymerize by radical initiation in emulsion to give polymers which were sticky, rubbery products and showed adhesive characteristics. Anionic initiation did not yield polymers with the α-alkylacrylonitriles containing high alkyl groups but did convert the C₂ to C₄ alkyl-substituted acrylonitriles to low molecular weight colored products. Some copolymers of α-alkylacrylonitriles with acrylonitrile were prepared in emulsion by radical initiation. The monomer ratios in these copolymers were determined by nuclear magnetic resonance spectra.     

Free radical induced oxidation of alkoxyphenols: Some insights into the processes of photoyellowing of papers

The photoyellowing of lignin-rich papers has been demonstrated to depend on the formation of phenoxyl radical intermediates and their ultimate conversion into various products, including quinones. Molecular oxygen has also been observed as a necessary adjunct to this process, although the mechanism is not understood. This work demonstrates the requirement for the reaction of O² with active radical intermediates (in processes analogous to autoxidation reactions) in order for the photoyellowing of the phenolic moieties to occur. Photo-oxidations of a variety of alkoxyphenols and their reactions with model alkyl, alkoxy and alkylperoxy radicals are studied by CIDEP.     

New Preparation of Bromoallenes

Bromoallenes are useful intermediates in organic synthesis (1) and also occur in a few natural products (2). They usually are prepared from propargylic alcohols by reaction with hydrobromic acid in the presence of cuprous bromide (2) but these conditions are usually drastic. A milder method has been reported but its scope is more limited (4).     

甲烷单加氧酶的催化反应机理研究*

本文就甲烷单加氧酶近年来在催化反应机理方面的最新研究成果进行了详细阐述。甲烷C—H 键的活化机理主要包括自由基回弹机理和协调的氧插入机理。运用自由基探针底物和量化计算等方法对烷烃羟基化反应机理的直接研究表明, 目前没有一个统一的机理来解释甲烷单加氧酶的反应过程。反应机理的类型可能取决于MMO 的来源或者其他因素。对甲烷单加氧酶的几种中间化合物的各种光谱学研究有力地推动了机理研究的发展。     

Thermochemistry and reaction paths in the oxidation reaction of benzoyl radical: C6H5C•(═O)

Alkyl substituted aromatics are present in fuels and in the environment because they are major intermediates in the oxidation or combustion of gasoline, jet, and other engine fuels. The major reaction pathways for oxidation of this class of molecules is through loss of a benzyl hydrogen atom on the alkyl group via abstraction reactions. One of the major intermediates in the combustion and atmospheric oxidation of the benzyl radicals is benzaldehyde, which rapidly loses the weakly bound aldehydic hydrogen to form a resonance stabilized benzoyl radical (C6H5C(?)═O). A detailed study of the thermochemistry of intermediates and the oxidation reaction paths of the benzoyl radical with dioxygen is presented in this study. Structures and enthalpies of formation for important stable species, intermediate radicals, and transition state structures resulting from the benzoyl radical +O2 association reaction are reported along with reaction paths and barriers. Enthalpies, ΔfH298(0), are calculated using ab initio (G3MP2B3) and density functional (DFT at B3LYP/6-311G(d,p)) calculations, group additivity (GA), and literature data. Bond energies on the benzoyl and benzoyl-peroxy systems are also reported and compared to hydrocarbon systems. The reaction of benzoyl with O2 has a number of low energy reaction channels that are not currently considered in either atmospheric chemistry or combustion models. The reaction paths include exothermic, chain branching reactions to a number of unsaturated oxygenated hydrocarbon intermediates along with formation of CO2. The initial reaction of the C6H5C(?)═O radical with O2 forms a chemically activated benzoyl peroxy radical with 37 kcal mol(-1) internal energy; this is significantly more energy than the 21 kcal mol(-1) involved in the benzyl or allyl + O2 systems. This deeper well results in a number of chemical activation reaction paths, leading to highly exothermic reactions to phenoxy radical + CO2 products.     

The reactions of cytidine and 2'-deoxycytidine with SO4.- revisited. Pulse radiolysis and product studies

The reactions of SO4.- with 2'-deoxycytidine 1a and cytidine 1b lead to very different intermediates (base radicals with 1a, sugar radicals with 1b). The present study provides spectral and kinetic data for the various intermediates by pulse radiolysis as well as information on final product yields (free cytosine). Taking these and literature data into account allows us to substantiate but also modify in essential aspects the current mechanistic concept (H. Catterall, M. J. Davies and B. C. Gilbert, J. Chem. Soc., Perkin Trans. 2, 1992, 1379). SO4.- radicals have been generated radiolytically in the reaction of peroxodisulfate with the hydrated electron (and the H. atom). In the reaction of SO4.- with 1a (k = 1.6 x 10(9) dm3 mol-1 s-1), a transient (lambda max = 400 nm, shifted to 450 nm at pH 3) is observed. This absorption is due to two intermediates. The major component (lambda max approximately 385 nm) does not react with O2 and has been attributed to an N-centered radical 4a formed upon sulfate release and deprotonation at nitrogen. The minor component, rapidly wiped out by O2, must be due to C-centered OH-adduct radical(s) 6a and/or 7a suggested to be formed by a water-induced nucleophilic replacement. These radicals decay by second-order kinetics. Free cytosine is only formed in low yields (G = 0.14 x 10(-7) mol J-1 upon electron-beam irradiation). In contrast, 1b gives rise to an intermediate absorbing at lambda max = 530 nm (shifted to 600 nm in acid solution) which rapidly decays (k = 6 x 10(4) s-1). In the presence of O2, the decay is much faster (k approximately 1.3 x 10(9) dm3 mol-1 s-1) indicating that this species must be a C-centered radical. This has been attributed to the C(5)-yl radical 8 formed upon the reaction of the C(2')-OH group with the cytidine SO4(.-)-adduct radical 2b. This reaction competes very effectively with the corresponding reaction of water and the release of sulfate and a proton generating the N-centered radical. Upon the decay of 8, sugar radical 11 is formed with the release of cytosine. The latter is formed with a G value of 2.8 x 10(-7) mol J-1 (85% of primary SO4.-) at high dose rates (electron beam irradiation). At low dose rates (gamma-radiolysis) its yield is increased to 7 x 10(-7) mol J-1 due to a chain reaction involving peroxodisulfate and reducing free radicals. Phosphate buffer prevents the formation of the sugar radical at the SO4(.-)-adduct stage by enhancing the rate of sulfate release by deprotonation of 2b and also by speeding up the decay of the C(5)-yl radical into another (base) radical. Cytosine release in cytidine is mechanistically related to strand breakage in poly(C). Literature data on the effect of dioxygen on strand breakage yields in poly(C) induced by SO4.- (suppressed) and upon photoionisation (unaltered) lead us to conclude that in poly(C) and also in the present system free radical cations are not involved to a major extent. This conclusion modifies an essential aspect of the current mechanistic concept.     

Carboxylate-substituted radicals from phenylselenide derivatives. Designs on models for coenzyme B12-dependent enzyme-catalyzed rearrangements

Laser flash photolysis (266 nm) of alpha- and beta-phenylselenyl esters, carboxylic acids, and carboxylates in aqueous acetonitrile media gave the corresponding radicals by homolytic cleavage of the phenylselenyl groups. In the beta-substituted systems, acid and carboxylate radicals reacted in intramolecular reporter reactions with approximately equal rate constants. For the alpha-substituted systems, an ester- and carboxylic acid-substituted radical reacted in an intramolecular reporter reaction with the same rate constants, but the analogous alpha-carboxylate radical, a radical anion, reacted an order of magnitude less rapidly and with an activation energy that is 3 kcal/mol greater than that found for analogues. A kinetic titration of the equilibrating alpha-acid and alpha-carboxylate radicals gave pKa = 4.6. The results indicate that alpha-ester and alpha-carboxylic acid radicals are unlikely to be appropriate models for alpha-carboxylate radicals, the intermediates formed in a large subset of coenzyme B12-dependent enzyme-catalyzed reactions.     

Radical and Heck cyclizations of diastereomeric o-haloanilide atropisomers

The outcomes of radical cyclizations and Heck reactions of N-(cyclohex-2-enyl)-N-(2-iodophenyl)acetamides depend critically on the configurations of the chiral axis and the stereocenter. In substrates without an ortho-methyl group, the diastereomeric precursors interconvert slowly at ambient temperatures. Cyclization of enriched mixtures of diastereomers provided similar yields of acetyl tetrahydrocarbazoles or dihydrocarbazoles, suggesting that interconversion of the radical or organometallic intermediates also occurs. Diastereomers of N-(cyclohex-2-enyl)-N-(2-iodo-4,6-dimethylphenyl)acetamides with an additional ortho-methyl group did not interconvert at ambient temperatures and were readily resolved. In radical cyclizations, syn diastereomers were prone to cyclize, while anti isomers were not. Strikingly, Heck reactions gave the opposite result; anti isomers were prone to cyclization and syn isomers were not. Heck reactions of allylic acetates occur with β-hydride elimination when acetate is trans to palladium and with β-acetoxy elimination when acetate is cis. This is surprising because prior studies have suggested that a trans relationship of palladium and acetoxy is essential for acetate elimination. Analyses of the results provide insights into mechanisms for radical cyclization and for insertion and elimination in the Heck reaction.