硝基苯甲酸酯水解反应单电子转移机理的证据: ESR和自旋捕获的研究

对-硝基苯甲酸甲酯(1), 对-硝基苯甲酸正丁酯(2), 对-硝基苯甲酸叔丁酯(3), 对-硝基苯甲酸苄酯(4), 对-硝基苯甲酸苯酯(5), 对-硝基苯甲酸(对-硝基)苯酯(6), 间-硝基苯甲酸甲酯(7), 间-硝基苯甲酸乙酯(8), 间-硝基苯甲酸苯酯(9)和3,5-二硝基苯甲酸甲酯(10)与氢氧化钾在二甲亚砜中反应, 反应产物分别为相应的对-硝基苯甲酸和间-硝基苯甲酸。反应液用ESR检测, 得到1-10自由基负离子的ESR谱。用自旋捕获技术证明反应过程中有OH自由基生成, 自由基捕获剂亚硝基叔丁烷(TNB), 苯基叔丁基硝酮(PBN)和氧气使产物硝基苯甲酸的产率降低, 结果表明, 1-10与KOH与DMSO中反应存在单电子转移机理。     

硝基苯甲酸酯水解反应单电子转移机理的证据: ESR和自旋捕获的研究

对-硝基苯甲酸甲酯(1),对-硝基苯甲酸正丁酯(2),对-硝基苯甲酸叔丁酯(3),对-硝基苯甲酸苄酯(4),对-硝基苯甲酸苯酯(5),对-硝基苯甲酸(对-硝基)苯酯(6),间-硝基苯甲酸甲酯(7),间-硝基苯甲酸乙酯(8),间-硝基苯甲酸苯酯(9)和3,5-二硝基苯甲酸甲酯(10)与氢氧化钾在二甲亚砜中反应,反应产物分别为相应的对-硝基苯甲酸和间-硝基苯甲酸.反应液用 ESR 检测,得到1—10自由基负离子的 ESR 谱.用自旋捕获技术证明反应过程中有·OH 自由基生成.自由基捕获剂亚硝基叔丁烷(TNB),苯基叔丁基硝酮(PBN)和氧气使产物硝基苯甲酸的产率降低.结果表明,1—10与 KOH 在 DMSO 中反应存在单电子转移机理.     

芳香族硝基化合物与苯硫酚钠盐的亲核取代反应: 自由基IPSO取代机理

化合物1,2,4和5与苯硫酚钠盐在二甲亚砜中反应,得到硝基被苯硫基取代的化合物和二苯基二硫化物.反应液用ESR检测,观察到化合物1,2,3和4自由基负离子的ESR信号.用自旋捕获(Spin trapping)技术得到苯硫基自由基PhS·与自由基捕获剂亚硝基叔丁烷(TNB)的加成物t-BuN(O)SPh,由ESR谱证实,表明在反应过程中有苯硫基自由基PhS·生成.提出自由基IPSO亲核取代反应机理.     

硫醇对炔属化合物的加成反应 Ⅴ.苯硫酚对几种炔烃加成的立体化学

苯硫酚与苯乙炔、对溴苯乙炔、对硝基苯乙炔及丙炔酸在室温进行直接加成时,生成相应的1:1加成物,其主体构型均属反式,分别为反-β-苯硫基苯乙烯(Ⅰa),反-β-苯硫基对溴苯乙烯(Ⅱa),反-β-苯硫基对硝基苯乙烯(Ⅲa)及反-β-苯硫基丙烯酸(Ⅳa)。加成物的得率按以下顺序而递減:Ⅰa>Ⅱa>Ⅲa>Ⅳa。在低温(-45～-35°)苯硫酚与四种炔烃在溶液中反应时,除对硝基苯乙炔不起反应外,其它三种炔化合物均给出全部或绝大部分顺式构型产物(反式加成),分别为顺-β-苯硫基苯乙烯(Ⅰb,100%),顺-β-苯硫基对溴苯乙烯(Ⅱb,75%)及顺-β-苯硫基丙烯酸(Ⅳb,80%)。所有顺式构型产物在反应条件下都稳定,只是在加热到160°以上时才转化为反式构型产物。苯硫酚对炔烃的直接加成为一自由基反应,所观察到的立体化学结果被解释为加成反应中形成的中间体自由基(Ⅴ),由于R(苯基或羧基)与处于顺式位置的C₆H₅S基的空间位阻,在与苯硫酚进行链转移之前发生异构化所致。因为Ⅴ的异构化为Ⅵ需要一定的活化能,故在低温下的加成全部或绝大部分按反式加成进行,在温度升高时全部转为顺式加成。苯硫酚与对硝基苯乙炔在无水乙醚中在—60°形成一深紫色溶液,两小时后颜色逐渐变淡,这似乎表明有自由基的形成。苯硫酚与四种炔化合物在乙氧基负离子催化下进行加成时,得到全部为反式加成的产物,分别为Ⅰb,Ⅱb,顺-β-苯硫基对硝基苯乙烯(Ⅲb)及Ⅳb。     

苯甲酸(苯并三唑基)苯酯类紫外光稳定剂的合成及表征

以邻硝基苯胺和间苯二酚为原料,经重氮化-偶合、环化、酯化合成了6个新型苯甲酸(苯并三唑基)苯酯类化合物:3-羟基-4-苯并三唑基-4′-硝基苯甲酸苯酯(58.6%)、3-羟基-4-苯并三唑基-2′-硝基苯甲酸苯酯(60.7%)、3-羟基-4-苯并三唑基-3′-硝基苯甲酸苯酯(55.7%)、3-羟基-4-苯并三唑基-3′,5′-二硝基苯甲酸苯酯(62.1%)、3-羟基-4-苯并三唑基-2′-羟基苯甲酸苯酯(48.6%)和3-羟基-4-苯并三唑基-2′-羟基-3′,5′-二硝基苯甲酸苯酯(52.2%)。通过1H-NMR、FT-IR和MS确定了这些化合物的分子结构,紫外光谱测试表明它们均具有较好的紫外吸收性能。     

乙烯基溴化镁与苯基取代氯甲烷反应的CIDNP效应

化学诱导动态核极化(CIDNP)巳广泛地用于研究溶液中的各种自由基反应。CIDNP研究表明,在Grignard试剂的生成以及Grignard试剂与卤代烃的反应中,很多是按自由基历程进行的。我们曾报道,乙烯基溴化镁(1)与三苯基氯甲烷(2)反应时,生成三苯基甲烷(4)和乙炔(5),并检测到反应溶液中三苯甲基自由基的ESR谱;1与二苯基氯甲烷(6)反应生成1,1,2,2-四苯基乙烷(7),二苯基甲烷(8),3,3-二苯基丙烯(9),1,3-丁二烯(10)和溴乙烯(11),并提出这些反应可能是通过自由基中间体进行的。为了进一步探讨反应机理,我们对题目化合物的反应进行了CIDNP实验,取得了一些很有意义的结果。     

尼达尼布的合成

间硝基苯甲酸甲酯(1)与氯乙酸甲酯反应制得4-甲氧基羰基甲基-3-硝基苯甲酸甲酯(2);2依次经催化氢化、乙酰化及与原苯甲酸三乙酯反应制得关键中间体(E)-1-乙酰基-3-(乙氧基-苯基-甲烯基)-2-氧-2,3-二氢-1H-吲哚-6-羧甲酸甲酯(5);N-甲基对硝基苯胺依次经氯乙酰化、取代和催化氢化反应制得N-(4-氨基苯基)-N-甲基-2-(4-甲基哌嗪-1-基)乙酰胺(9);5和9经拼合合成了治疗特发性肺纤维化药尼达尼布,总收率22.0%,纯度99.4%,其结构经1H NMR和MS确证。     

2-烃基-1,3-二氧甲基甘油的合成

通过1,3-二甲氧基丙酮的格氏反应,合成了五个2-烃基-1,3-二氧甲基甘油(2)。烃基分别为甲基、苯基、正丁基、环戊基和环己基。对-硝基苯甲酸酯和3,5-二硝基苯甲酸酯经分析鉴定。2的直接对-甲苯磺酰化未能成功。     

4-(5-硝基-6-羟基-2-苯并(噁)唑基)苯甲酸甲酯的合成

研究了以关键中间体4-氨基-6-硝基间苯二酚盐酸盐(ANR·HCl)和对苯二甲酸单甲酯(MTA)为原料,分别经酰氯化、缩合、环合分步或原位合成AB型新单体前体-4-(5-硝基-6-羟基-2-苯并唑基)苯甲酸甲酯(MNB)的技术. 反应优化条件为:在甲基异丁基酮溶剂中,n(ANR·HCl)∶ n(MTA)=1.00∶ 1.03,115 ℃缩合反应2.5 h,m(ANR·HCl)∶ m(PPA)=1.00∶ 3.25的多聚磷酸(PPA),120 ℃环合8.5 h,MNB收率75.68%(以ANR·HCl计),HPLC测定ω(MNB)=96.32%. 产物结构经1H NMR和IR测试技术得以确证.     

7-取代-4-喹诺酮-2-羧酸甲酯的合成

4-喹诺酮-2-羧酸甲酯衍生物的制备,一般是用苯胺衍生物与丁炔二酸二甲酯反应,生成α-(取代苯胺基)丁烯二酸二甲酯(1),继之在二苯醚中约260℃加热环合而获得。我们用间氨基苯酚与丁炔二酸二甲酯在甲醇中反应,所得黄色固体经鉴定为7-羟基-4-喹诺酮-2-羧酸甲酯(2);除去固体后的滤液在甲醇-盐酸中回流还能生成2。若用间苯二胺与丁炔二酸二甲酯反应,则生成7-氨基-4-喹诺酮-2-羧酸甲酯(3)(产率20%)和N,N′-二(1,2-双-甲氧羰基乙烯基)间苯二胺(4)(产率4.8%)。这样就不需要再在二苯醚中进行环合。2与3的易于制备,显示氨基和羟基的活化作用。2和3在室温分别与醋酐-吡啶反应,可得乙酰化物5和6.2和3在二甲基甲酰胺中与乙氧草酰氯(ethyloxalyl chloride)反应,可分别生成化合物7和8。     

p-硝基氯苯与α氰基乙酸乙酯-α-碳负离子的电子转移反应动力学研究: 非链式的自由基机理

在p-硝基氯苯(1)与α-氰基乙酰乙酯-α-碳负离子(2)的反应过程中, 测得了反应中间体p-硝基氯苯负离子自由基(3)的ESR谱。用ESR场/频联锁技术测定了(3)的ESR吸收强度-时间曲线, 当[1]《[2]时, 其结果与连续一级反应动力学相吻合。测得了从2向1的电子转移和3的分解反应速率常数和活化参数, 反应产物为α-氰基-α-(p-硝基苯基)乙酸乙酯和微量的硝基苯。为该反应提出了非链式的电子转移-负离子自由基分解-自由基偶合机理。     

Novel rhodium and ruthenium carbonyl cluster complexes with face- and edge-bridging GaCp* ligands. Synthesis and structural characterization of the Rh6(CO)12(mu3-GaCp*)4 and Ru6(eta6-C)(mu2-CO)(CO)13(mu3-GaCp*)2(mu2-GaCp*) clusters

Reactions of hexanuclear carbonyl clusters of rhodium Rh(6)(CO)(16) and ruthenium Ru(6)(eta(6)-C)(micro(2)-CO)(CO)(16) with GaCp*(Cp*= C(5)Me(5)) in the mild conditions result in substitution of CO ligands and formation of the Rh(6)(CO)(12)(micro(3)-GaCp*)(4) and the Ru(6)(eta(6)-C)(micro(2)-CO)(CO)(13)(micro(3)-GaCp*)(2)(micro(2)-GaCp*) cluster derivatives.     

Reactivity of molecular oxygen with ethoxycarbonyl derivatives of tetrathiatriarylmethyl radicals

Tetrathiatriarylmethyl (TAM) radicals are commonly used as oximetry probes for electron paramagnetic resonance imaging applications. In this study, the electronic properties and the thermodynamic preferences for O2 addition to various TAM-type triarylmethyl (trityl) radicals were theoretically investigated. The radicals' stability in the presence of O2 and biological milieu was also experimentally assessed using EPR spectroscopy. Results show that H substitution on the aromatic ring affects the trityl radical's stability (tricarboxylate salt 1-CO2Na > triester 1-CO2Et > diester 2-CO2Et > monoester 3-CO2Et) and may lead to substitution reactions in cellular systems. We propose that this degradation process involves an arylperoxyl radical that can further decompose to alcohol or quinone products. This study demonstrates how computational chemistry can be used as a tool to rationalize radical stability in the redox environment of biological systems and aid in the future design of more biostable trityl radicals.     

四甲基硅锗桥连双环戊二烯基及双(四甲基环戊二烯基)四羰 基二铁的合成、结 构及热重排反应

1,2-二氯四甲基硅锗烷分别与环戊二烯基锂及四甲基环戊二烯基锂反应得到两个新的双齿配体：C5H5Me2SiGeMe2C5H5(9)和C5HMe4Me2SiGeMe2C5HMe4(10).配体9和10分别与Fe(CO)5在二甲苯中加热生成四甲基硅锗桥连双环戊二烯基四羰基二铁(11)和四甲基硅锗桥连双(四甲基环戊二烯基)四羰基二铁(13).11和13均可发生热重排反应,生成[(η^5-C5R4)Fe(CO)2]2(μ-Me2Si)(μ-Me2Ge)(R=H,12;R=Me,14)。测定了化合物11,12,13及14的晶体结构,讨论了桥连四甲基环戊二烯基配体的位阻效应对其某些结构参数以及重排反应性的影响。     

Reversible cleavage and recombination of an acetylenic carbon-carbon bond on a tetrairon cluster coupled with a two-electron redox reaction

Two-electron reduction of [(eta5-C5H4Me)4Fe4(mu3-CH)2(mu3-CO)2](PF6)2 (1) results in the coupling of two methylidyne ligands to form (eta5-C5H4Me)4Fe4(HCCH)(mu3-CO)2 (2), the two-electron oxidation of which reproduces 1. Structures of 1 and 2 were determined by X-ray diffraction analysis.     

脂族酰基过氧化物分解动力学的研究X: 过氧化酰热分解反应的自旋捕获ESR研究

用亚硝基丁烷(TNB)、亚硝基苯和C-苯基-N-叔丁基硝酮作为自旋捕获剂来捕获和检出一些二酰基过氧化物类化合物分解时形成的短命烷基自由基. 报导了烷基自由基对自旋捕获剂加成的氮氧化物自由基的电子自旋共振谱, 并观察到2,4,4-三甲基戊基自由基中α-CH2的氢是非对映和非等价的. 据此, 认为与这一类自由基的加合物产生的电子自旋共振谱与其它类型自由基是不同的.     

Cationic diiron and diruthenium μ-allenyl complexes: synthesis, X-ray structures and cyclization reactions with ethyldiazoacetate/amine affording unprecedented butenolide- and furaniminium-substituted bridging carbene ligands

The novel cationic diiron μ-allenyl complexes [Fe(2)Cp(2)(CO)(2)(μ-CO){μ-η(1):η(2)(α,β)-C(α)(H)=C(β)=C(γ)(R)(2)}](+) (R = Me, 4a; R = Ph, 4b) have been obtained in good yields by a two-step reaction starting from [Fe(2)Cp(2)(CO)(4)]. The solid state structures of [4a][CF(3)SO(3)] and of the diruthenium analogues [Ru(2)Cp(2)(CO)(2)(μ-CO){μ-η(1):η(2)(α,β)-C(α)(H)=C(β)=C(γ)(R)(2)}][BPh(4)] (R = Me, [2a][BPh(4)]; R = Ph, [2c][BPh(4)]) have been ascertained by X-ray diffraction studies. The reactions of 2c and 4a with Br?nsted bases result in formation of the μ-allenylidene compound [Ru(2)Cp(2)(CO)(2)(μ-CO){μ-η(1):η(1)-C(α)=C(β)=C(γ)(Ph)(2)}] (5) and of the dimetallacyclopentenone [Fe(2)Cp(2)(CO)(μ-CO){μ-η(1):η(3)-C(α)(H)=C(β)(C(γ)(Me)CH(2))C(=O)}] (6), respectively. The nitrile adducts [Ru(2)Cp(2)(CO)(NCMe)(μ-CO){μ-η(1):η(2)-C(α)(H)=C(β)=C(γ)(R)(2)}](+) (R = Me, 7a; R = Ph, 7b), prepared by treatment of 2a,c with MeCN/Me(3)NO, react with N(2)CHCO(2)Et/NEt(3) at room temperature, affording the butenolide-substituted carbene complexes [Ru(2)Cp(2)(CO)(μ-CO){μ-η(1):η(3)-C(α)(H)[upper bond 1 start]C(β)C(γ)(R)(2)OC(=O)C[upper bond 1 end](H)] (R = Me, 10a; R = Ph, 10b). The intermediate cationic compound [Ru(2)Cp(2)(CO)(μ-CO){μ-η(1):η(3)-C(α)(H)[upper bond 1 start]C(β)C(γ)(Me)(2)OC(OEt)C[upper bond 1 end](H)](+) (9) has been detected in the course of the reaction leading to 10a. The addition of N(2)CHCO(2)Et/NHEt(2) to 7a gives the 2-furaniminium-carbene [Ru(2)Cp(2)(CO)(μ-CO){μ-η(1):η(3)-C(α)(H)[upper bond 1 start]C(β)C(γ)(Me)(2)OC(OEt)C[upper bond 1 end](H)](+) (11). The X-ray structures of 10a, 10b and [11][BF(4)] have been determined. The reactions of 4a,b with MeCN/Me(3)NO result in prevalent decomposition to mononuclear iron species.     

A phosphine-mediated through-space exchange coupling pathway for unpaired electrons in a heterobimetallic lanthanide-transition metal complex

The reaction of P(CH2OH)3 with methyl anthranilate NH2C6H4-2-CO2Me produced the ligand precursor P(CH2NHC6H4-2-CO2Me)3 (1). The reaction of 1 with [Y{N(SiMe3)2}3] produced hexadentate yttrium complex [Y{P(CH2NC6H4-2-CO2Me)3}] (2), in which the metal centre is coordinated by three amido donors and the three carbonyl oxygen atoms of the ester groups. The 31P{1H} NMR spectrum features 1J Y,P=15 Hz, and DFT calculations demonstrate that through-space interaction between the minor lobe of the phosphine lone pair and the yttrium centre allows a large Fermi contact contribution to this spin coupling constant. The EPR spectrum of the analogous paramagnetic Gd complex [Gd{P(CH2NC6H4-2-CO2Me)3}] (3) can be modelled by using a B20 crystal field parameter of +/-0.19 cm(-1). Heterodinuclear complexes were prepared by the reactions of 1 and 3 with [5,10,15,20-tetrakis(4-methoxyphenyl)porphinato]cobalt(II), by binding of the phosphine lone pair to the d(7) cobalt centre. The solid-state EPR spectrum of the heterodinuclear yttrium complex 4 exhibits large superhyperfine coupling to the phosphorus nucleus, indicative of an S=1/2 complex in which the unpaired electron resides in the cobalt dz2 orbital directed at the phosphine donor. The magnetic susceptibility of the heterodinuclear Gd-Co complex 5 demonstrates that through-space antiferromagnetic coupling occurs between unpaired electrons on the gadolinium and cobalt centres.     

Binuclear palladium(I) and palladium(II) complexes of ortho-functionalized 1,3-bis(aryl)triazenido ligands

Three new bis(aryl)triazene ligands, Ar-NNNH-Ar' [Ar = o-C(6)H(4)-CO(2)Me, Ar' = p-C(6)H(4)-CH(3) (2); Ar = Ar' = o-C(6)H(4)-CO(2)Me (3); Ar = o-C(6)H(4)-SMe, Ar' = p-C(6)H(4)-CH(3)) (4)], have been synthesized. The reaction of 1-4 with PdCl(2)(NCCH(3))(2) in the presence of a base afforded a series of binuclear diamagnetic palladium complexes. In these reactions, ligands 1-3 afforded the palladium(I) complexes [Pd(I)(o-MeO(2)C-C(6)H(4)-NNN-o-C(6)H(4)-CO(2)Me)](2) (5, monoclinic, space group P21/c, a = 8.6070(10) Angstrom, b = 14.3220(10) Angstrom, c = 12.7310(10) Angstrom, beta = 100.2950(10) degrees, Z = 2), [Pd(I)(o-MeO-C(6)H(4)-NNN-o-C(6)H(4)-OMe)](2) (6, triclinic, space group P, a = 6.6288(5) Angstrom, b = 10.2631(10) Angstrom, c = 11.0246(11) Angstrom, alpha = 85.579(6) degrees, beta = 80.885(6) degrees, gamma = 74.607(6) degrees, Z = 1), and [Pd(I)(o-MeO(2)C-C(6)H(4)-NNN-p-C(6)H(4)-CH(3))](2) (7, tetragonal, space group I41/a, a = 20.866(3) Angstrom, b = 20.866(3) Angstrom, c = 13.156(2) Angstrom, Z = 8). In contrast, the reaction of ligand 4 with PdCl(2)(NCCH(3))(2) resulted in the formation of a palladium(II) dimer, [Pd(II)(o-MeS-C(6)H(4)-NNN-p-C(6)H(4)-CH(3))Cl](2) (8, orthorhombic, space group P2(1)2(1)2, a = 10.4058(5) Angstrom, b = 16.2488(8) Angstrom, c = 9.9500(5) Angstrom, Z = 2).     

Electron spin resonance studies of azasemiquinone free radical intermediates in the oxidation of hydroxypyridones

The oxidation of hydroxy-2-pyridones by a number of one-electron oxidants has been studied, and intermediate free radicals observed by ESR spectroscopy. In alkaline media, azasemiquinones arising from electron transfer, solvation and oxidative coupling processes have been detected. The ESR hyperfine splittings are assigned with the aid of Me substitution, and the spin densities can be understood by considering the perturbation of the N atom within the semiquinone nucleus. In acid solution, the protonation of nitrogen produces structural changes in the semiquinone nucleus, which greatly affect the spin density distributions. The apparent lifetimes of the various radical species can be correlated with their expected tendencies to direct free radical dimerisation.