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Virgil Barboiu Marian N. Holerca Emilia Streba Cornelia Luca 《Journal of polymer science. Part A, Polymer chemistry》1996,34(2):261-270
A detailed study of the synthesis of betaine products that result from addition reactions of poly (4-vinylpyridine) and poly (N-vinylimidazole) as well as of their model compounds, with α,β-unsaturated monocarboxylic acids is presented. A reaction mechanism based on experimental observations and proved by kinetic analysis is proposed. It consists of two reactions: the addition, which involves two molecules of acid and leads to X+B−-like structures, where the cation X+ results from the addition of the amino nitrogen to the double bond of acid and B− is the carboxyl anion, and an equilibrium reaction between X+B− and the betaine structure X±. The latter occurs only in protic solvents and is coupled with the addition reaction. The process was especially investigated in methanol, because this solvent allows determination of the kinetic parameters. Some values of the addition rate constants are given. The study is based on 1H-NMR measurements and observations. © 1996 John Wiley & Sons, Inc. 相似文献
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Virgil Brboiu Emilia Streba Cornelia Luca Cristofor I. Simionescu 《Journal of polymer science. Part A, Polymer chemistry》1995,33(3):389-398
The reactions of vinylpyridine polymers with α,β-unsaturated carboxylic acids such as acrylic, methacrylic, crotonic, itaconic, cinnamic, fumaric, and maleic acids were studied. It was found that, when reacted with acrylic, itaconic and fumaric acids. poly(4-vinylpyridine) gave macromolecular betaine products while with maleic acid, betaine as well as the corresponding salt was obtained. Poly(2-vinylpyridine) reacted with the same acids as poly(4-vinylpyridine) gave only the salts. No significant changes were observed with the two polymers when reacted with methacrylic, crotonic, and cinnamic acids. To attempt to rationalize these observations with the two macromolecular tertiary amines, the reactions of 4-methyl and 2-methylpyridines with the same carboxylic acids were investigated. The 1H-NMR methodology was generally applied to elucidate the chemical structure obtained. © 1995 John Wiley & Sons, Inc. 相似文献
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Guo Ping LI Wei Ren XU Xian Jie LIN Cheng Bu LIU 《中国化学快报》2006,17(3):423-426
Nitrones are useful in the preparation of many interesting compounds such as amino aldehydes, aminosugars, aza sugars, amino acids, aminoalcohols, peptide isosteres and nucleoside analogs. Nitrones are generally prepared by the condensation reactions of c… 相似文献
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Dr. Yasuhiro Yamashita Dr. Hirotsugu Suzuki Io Sato Tsubasa Hirata Prof. Dr. Shū Kobayashi 《Angewandte Chemie (International ed. in English)》2018,57(23):6896-6900
Catalytic addition reactions of very weakly acidic nonactivated alkylarenes such as toluene and its derivatives were developed by using a strongly basic mixed catalyst system under mild reaction conditions. The addition reactions with imines and alkenes proceeded smoothly under proton‐transfer conditions to afford the desired products in good to high yields, and high levels of regio‐ and stereoselectivity were achieved. It was also revealed that the asymmetric addition reaction of an alkylarene was possible. 相似文献
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Véronique Plantevin 《Journal of organometallic chemistry》2004,689(11):2013-2024
Further investigations into the chemistry of the rhenacyclobutadiene complexes (CO)4Re(η2-C(R)C(CO2Me)C(X)) (1: R=Me, X=OEt (1a), O(CH2)3CCH (1b), NEt2 (1c); R=CHEt2, X=OEt (1d); R=Ph, X=OEt (1e)) are reported. Reactions of 1 with alkynes at reflux temperature of toluene and at ambient temperature either under photochemical conditions or in the presence of PdO yield ring-substituted η5-cyclopentadienylrhenium tricarbonyl complexes, 2. The symmetrical alkynes R′CCR′ (R′=Ph, Me, CO2Me) afford the pentasubstituted complexes (η5-C5(Me)(CO2Me)(OEt)(Ph)(Ph))Re(CO)3 (2d), (η5-C5(Me)(CO2Me)(OEt)(Me)(Me))Re(CO)3 (2e), (η5-C5(Me)(CO2Me)(OEt)(CO2Me)(CO2Me))Re(CO)3 (2f), and (η5-C5(Me)(CO2Me)(NEt2)(CO2Me)(CO2Me))Re(CO)3 (2i) on reaction with the appropriate 1, whereas the unsymmetrical alkynes R′CCR″ (R′=Ph; R″=H, Me) give either only one, (η5-C5(Me)(CO2Me)(OEt)(Ph)H)Re(CO)3 (2a)), or both, (η5-C5(Me)(CO2Me) (OEt)(Ph)(Me))Re(CO)3 (2b) and (η5-C5(Me)(CO2Me)(OEt)(Me)(Ph))Re(CO)3 (2c), (η5-C5(Ph)(CO2Me)(OEt)(Ph)H)Re(CO)3 (2g) and (η5-C5(Ph)(CO2Me)(OEt)(H)(Ph))Re(CO)3 (2h), of the possible products of [3 + 2] cycloaddition of alkyne to η2-C(R)C(CO2Me)C(X). Thermolysis of (CO)4Re(η2-C(Me)C(CO2Me)C(O(CH2)3CCH)) (1b) containing a pendant alkynyl group proceeds to (η5-C5(Me)(CO2Me)(O(CH2)3)H)Re(CO)3 (2j), a η5-cyclopentadienyl-dihydropyran fused-ring product. Competition experiments showed that each of PhCCH and MeO2CCCCO2Me reacts faster than PhCCPh with 1a. The results with unsymmetrical alkynes are rationalized by steric properties of substituents at the CC and ReC bonds and by a preference of ReC(Me) over ReC(OEt) to undergo alkyne insertion. A mechanism is proposed that involves substitution of a trans CO by alkyne in 1, insertion of alkyne into ReC bond to give a rhenabenzene intermediate, and collapse of the latter to 2. Complexes 1a and 1d undergo rearrangement in MeCN at reflux temperature to give rhenafuran-like products, (CO)4Re(κ2-OC(OMe)C(CHCR2)C(OEt)) (R=H (3a) or Et (3b)). The reaction of 1d also proceeds in EtCN, PhCN, and t-BuCN at comparable temperature, but is slower (especially in t-BuCN) than in MeCN. In pyridine at reflux temperature, 1a undergoes a similar rearrangement, with CO substitution, to give (CO)3(py)Re(κ2-OC(OMe)C(CHCEt2)C(OEt)) (4). A mechanism is proposed for these reactions. The sulfonium ylides Me2SCHC(O)Ph and Me2SC(CN)2 (Me2SCRR′) react with 1a in acetonitrile at reflux temperature by nucleophilic addition of the ylide to the ReC(Me) carbon, loss of Me2S, and rearrangement to a rhenafuran-type structure to yield (CO)4Re(κ2-OC(OMe)C(C(Me)CRR′)C(OEt)) (R=H, R′=C(O)Ph (5a); R=R′CN (5b)). All new compounds were characterized by a combination of elemental analysis, mass spectrometry, and IR and NMR spectroscopy. 相似文献
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Side-chain liquid crystalline (SCLC) silphenylene-siloxane polymers with a phenyl benzoate mesogenic group and polymethylene spacers were prepared and characterized, and their properties were compared with those of equivalent SCLC polymers, SCLCPs, with a biphenyl mesogenic group. With identical spacers and terminal substituents, the melting temperatures of the former were much lower, but the isotropization temperatures were lowered to a lesser extent, than those of the latter, and, consequently, a more thermally stable nematic phase was obtained for the former. Both types of SCLCPs formed nematic phases, while polymethylsiloxanes with the same side-chain mesogens exhibited smectic phases with wider temperature ranges. The lower thermal stability of the mesophases in the silphenylene-siloxane SCLCPs compared to those of the SCLC polymethylsiloxanes can be attributed to both the rigidity of the backbone and the greater separation of the side-chains along the main chains of the former. 相似文献
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含有α-H的烯烃可以与溴自由基发生自由基加成和自由基取代反应。本文以丙烯为例,论述了自由基加成和取代反应的机理和竞争关系,从而帮助读者更好地理解反应条件对优势反应及产物的影响。 相似文献
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Addition Reactions of Me3SiCN with Aldehydes Catalyzed by Aluminum Complexes Containing in their Coordination Sphere O,S, and N Ligands
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Prof. Zhi Yang Yafei Yi Dr. Mingdong Zhong Sriman De Totan Mondal Dr. Debasis Koley Dr. Xiaoli Ma Dr. Dongxiang Zhang Prof. Herbert W. Roesky 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(20):6932-6938
The reaction of one equivalent of LAlH2 ( 1 ; L=HC(CMeNAr)2, Ar=2,6‐iPr2C6H3, β‐diketiminate ligand) with two equivalents of 2‐mercapto‐4,6‐dimethylpyrimidine hydrate resulted in LAl[(μ‐S)(m‐C4N2H)(CH2)2]2 ( 2 ) in good yield. Similarly, when N‐2‐pyridylsalicylideneamine, N‐(2,6‐diisopropylphenyl)salicylaldimine, and ethyl 3‐amino‐4,5,6,7‐tetrahydrobenzo[b]thiophene‐2‐carboxylate were used as starting materials, the corresponding products LAl[(μ‐O)(o‐C6H4)CN(C5NH4)]2 ( 3 ), LAlH[(μ‐O)(o‐C4H4)CN(2,6‐iPr2C6H3)] ( 4 ), and LAl[(μ‐NH)(o‐C8SH8)(COOC2H5)]2 ( 5 ) were isolated. Compounds 2 – 5 were characterized by 1H and 13C NMR spectroscopy as well as by single‐crystal X‐ray structural analysis. Surprisingly, compounds 2 – 5 exhibit good catalytic activity in addition reactions of aldehydes with trimethylsilyl cyanide (TMSCN). 相似文献
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利用水热法合成了2种新的双咪唑及二元羧酸配体镉配合物[Cd(sdc)(bipe)]·H_2O(1)和[Cd(bpdc)(bipe)(H_2O)](2)[bipe=bis(4-imidazolphenoxy)ethane,H_2sdc=4,4’-sulfonyldibenzoic acid,H_2bpdc=biphenyl-4,4’-dicarboxylic acid].通过元素分析、红外光谱(IR)、X射线单晶衍射和热重分析(TG)等方法对其进行表征,并测试了2种化合物的荧光性质.化合物1展示了一个具有{4~4·6~2}拓扑的(4,4)-连接的sql二维空间网络结构,配体与金属间荷移跃迁化合物2显示了一个具有(4~(12)·6~3)的六连接pcu网状拓扑结构.荧光测试结果显示,配体与金属间发生的荷移跃迁使得化合物1和2的荧光发射峰与配体bipe相比明显发生了红移. 相似文献
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Five iron(II) coordination polymers, {[Fe(bte)2(NCS)2][Fe(bte)(H2O)2(NCS)2]}n (1), [Fe(bime)(NCS)2]n (2), [Fe(bime)(dca)2]n (3), [Fe(bime)2(N3)2]n (4) and [Fe(btb)2(NCS)2]n (5), were synthesized using the flexible ligands 1,2-bis(1,2,4-triazol-1-yl)ethane (bte), 1,2-bis(imidazol-1-yl)ethane (bime) and 1,4-bis(1,2,4-triazol-1-yl)butane (btb), together with NCS−, dicyanamide (dca) and N3−. The compound 1 contains two kinds of motifs (double chain and single chain) and forms a three-dimensional hydrogen bonded network; 2 and 3 contain one-dimensional triple chains; and 4 and 5 form two-dimensional (4, 4) networks. The coordination anions (NCS−, dca and N3−) and the structural characteristics of the ligands (bte, bime and btb) play an important role in the assembly of the topologies. Magnetic studies reveal that 1-5 remain in the high-spin state over the whole temperature range 2-300 K and no detectable spin-crossover is observed. 相似文献
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Dr. Hai-xuan Liu Dr. Fei Ji Yu Chen Ya Gao Jun-ke Wang Dr. Ming-zhi Zhang Dr. Fang Liu Dr. Qiang Sha 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(16):5225-5229
Herein, a divergent synthesis of a variety of 2α- and 5α-substituted furan derivatives from 2-hydroxy-1,4-diones is reported. By using appropriate substrates and an acid catalyst, the reactions occurred selectively through cyclization/1,6-conjugate addition or cyclization/Friedel–Crafts-type cascade reactions. A broad range of nucleophilic reagents (>10 types for the 1,6-conjugate addition for 5α substitution and >20 types for the Friedel–Crafts-type cascade reaction for 2α substitution), including alcohols, amides, furan, thiophene, pyrrole, indole, phenols, and many others, can successfully participate in the reactions, providing a universal strategy for a diversity-oriented synthesis of α-substituted furan derivatives. Deuteriation experiments and DFT calculations were carried out to support the proposed reaction mechanisms. Antifungal activity experiments revealed that products with an indole or 4-hydroxycoumarin core substituted at the 2α position showed moderate activities against Rhizoctorzia solani and Botrytis cinerea, respectively. 相似文献
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《Chemphyschem》2004,5(2):225-232
Kinetics and mechanism for the reaction of phenyl radical (C6H5) with ketene (H2Cβ?Cα?O) were studied by the cavity ring‐down spectrometric (CRDS) technique and hybrid DFT and ab initio molecular orbital calculations. The C6H5 transition at 504.8 nm was used to detect the consumption of the phenyl radical in the reaction. The absolute overall rate constants measured, including those for the reaction with CD2CO, can be expressed by the Arrhenius equation k=(5.9±1.8)×1011 exp[?(1160±100)/T] cm3 mol?1 s?1 over a temperature range of 301–474 K. The absence of a kinetic isotope effect suggests that direct hydrogen abstraction forming benzene and ketenyl radical is kinetically less favorable, in good agreement with the results of quantum chemical calculations at the G2MS//B3LYP6‐31G(d) level of theory for all accessible product channels, including the above abstraction and additions to the Cα, Cβ, and O sites. For application to combustion, the rate constants were extrapolated over the temperature range of 298–2500 K under atmospheric pressure by using the predicted transition‐state parameters and the adjusted entrance reaction barriers Eα=Eβ=1.2 kcal mol?1; they can be represented by the following expression in units of cm3 mol?1 s?1: kα=6.2×1019 T?2.3 exp[?7590/T] and kβ=3.2×104 T2.4 exp[?246/T]. 相似文献
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