通过α-重氮-β-二酮与醛酮的环加成反应合成4H-1,3-二噁环己-5-烯-4-酮衍生物

研究了α-重氮-β-二酮与各类羰基化合物的环加成反应,合成了一系列4H-1,3-二噁环己-5-烯-4-酮衍生物.     

无外加催化剂条件下邻取代芳香醛与5,5-二甲基-1,3-环己二酮的反应研究

在DMF溶剂中,不外加催化剂使邻取代芳香醛(1)与5,5-二甲基-1,3-环己三酮(2)发生缩合和加成反应生成3,3,6,6-四甲基-4a-羟基-9-芳基-1,8二氧化-2,3,4,4a,5,6,7,8,9a-十氢化-1H氧杂蒽(3a～3d)。在同样条件下,邻羟基芳香醛与5,5-二甲基-1,3-环己三酮则发生缩合,加成和脱水反应生成3,3-二甲基-9-(5,5-二甲基-3-羟基-2-环己烯-1-酮-2-基)-1-氧代-2,3,4,9-四氢化-1 氧杂蒽(4a～4b)。用单晶X-射线分析法确定了产物3a和4a的晶体结构。     

离子液体中5,5-二甲基-1,3-环己二酮与N-芳亚甲基芳胺反应合成 吖啶衍生物

在离子液体[bmim]Br中, 5,5-二甲基-1,3-环己二酮与N-芳亚甲基芳胺反应合成了一系列四氢吖啶-1,8-二酮衍生物, 该反应具有适应性广、产率高、污染少、环境友好等优点.     

2 ,2-二取代-1,3-环戊二酮的Baeyer-Villiger氧化反应

研究了 2 ,2 -二取代 - 1 ,3-环戊二酮的Baeyer_Villiger氧化反应 ,合成了 4个新的 5,5-二取代 - 4-氧代 -δ -内酯 ,它们的结构通过IR、1 HNMR和元素分析予以确定。     

苯甲酰-1,3-环己二酮类化合物互变异构的理论计算

对苯甲酰-1,3-环己二酮的各异构体进行了HF/6-31G＊水平的几何优化,然后对能量低的三酮式和2个顺式烯醇式异构体进行了更广泛的计算,探讨了计算方法、基组大小对异构体相对稳定性的影响。在此基础上,对该类化合物的互变异构化平衡常数、能垒进行了计算,在平衡常数的计算中充分考虑了溶剂的影响并结合实验结果进行了分析。最后,对有代表性的苯环2-位取代衍生物进行了计算,发现互变异构自由能与其HPPD酶抑制活性间存在着较好的相关关系。     

3-芳胺甲烯基-5,6-二氢-二氢吡喃-2,4-二酮类化合物催化氢化反应选择性的理论研究

用分子力学方法、AM1半经验方法以及从头算密度泛函B3LYP/6-311G^**方法研究了3-芳胺甲烯基-5,6-二氢-二氢吡喃-2,4-二酮类化合物在催化氢化反应中影响反应选择性的因素,结果表明,R基团对自由基中间物稳定性的影响决定了反应选择性.     

3-丙烯酰基-1,3-噁唑烷-2-酮的合成

3-α,β-不饱和酰基-1,3-噁唑烷-2-酮在烷基化及Diels-Alder等反应中在手性催化剂的存在下,产物都有较高的对映选择性。但3-丙烯酰基-3,3-噁唑烷-2-酮极易聚合,现有制备方法结果均不理想。本文将丙烯酸与丙烯酰氯在三乙胺的存在下生成酸酐,再在无水氯化锂的作用下与1,3-噁唑烷-2-酮在室温反应,反应结束后直接将反应混合物通过硅胶柱色谱进行层析分离得到3-丙烯酰基-1,3-噁唑烷-2-酮,产率达83％。合成路线如下：     

3-酰基-2,4-吡咯烷二酮及其N-酰基衍生物相对稳定性的理论计算

对 3 酰基 2 ,4 吡咯烷二酮 (1)及其N 酰基衍生物 (2 )的各种异构体 (a -e)分别进行了HF/6 31G和HF/6 31G 水平上的优化计算 ,并考虑电子相关效应 (MP2 /6 31G )对其能量进行了校正 ,探讨了计算水平对体系相对稳定性的影响。HF/6 31G 及MP2 /6 31G 上的计算结果表明 1d和 2a分别为化合物 1和 2的最稳定结构形式 ,与实验观察到的结果一致。同时对N 位取代酰基引起的优势结构的变化给出了较合理的解释。     

功能离子液体水相催化芳醛与5,5-二甲基-1,3-环己二酮的反应

以N,N,N′,N′-四甲基乙二胺、1,3-丙磺酸内酯为原料,经酸化合成了功能化离子液体N,N,N′,N′-四甲基-N,N′-二磺丙基二硫酸氢盐(TSIL). TSIL离子液体兼具Brnsted 酸性官能团和季铵盐相转移催化剂的结构,能够实现水相中芳醛与5,5-二甲基-1,3-环己二酮反应,得到氢化氧杂蒽衍生物. 结果表明,合成的TSIL具有较高的催化活性,在水相中于100 ℃下回流2～3 h即可完成反应,产率可达80%～93%. 反应生成的取代氢化氧杂蒽与离子液体的水溶液不相溶,通过简单的过滤可实现产物与催化体系的分离,简化了分离过程,方法操作简便、环境友好、催化剂可回收并重复使用.     

N－（2－环戊酮基丙酰基）－及N－（2－环己酮基丙酰基）－四氢噻唑－2－硫酮的合成及其醇解与胺解

以碘化－Ｎ－甲基－２－氯吡啶盐为缩合剂，在三乙胺存在下由３－（２－环戊酮基）丙酸及３－（２－环己酮基）丙酸分别同四氢噻唑－２－硫酮反应，得到新化合物Ｎ－（２－环戊酮基内酰基）四氢噻唑－２－硫酮（２ａ）及Ｎ－（２－环己酮基丙酰基）四氢噻唑－２－硫酮（２ｂ），产率分别为５２．９％和５１．０％，２ａ，ｂ分别同甲醇、乙醇反应得到相应的３－（２－环戊酮基）丙酸酯３ａ，ｂ及３－（２－环己酮基）丙酸酯３ｃ，ｄ，３ａ～ｄ的产率为７５～８７％；２ａ、ｂ分别同胺反应得到３－（２－环戊酮基）内酰胺４ａ、ｂ及３－（２－环己酮基）内酰胺４ｃ、ｄ，４ａ～ｄ产率为７８～９３％。     

Density functional theory study of tautomerization of 2‐aminothiazole in the gas phase and in solution

The amino/imino tautomeric equilibrium in the isolated, mono‐, di‐, and trihydrate forms and dimer of 2‐aminothiazole, and the effects of hydration or self‐assistance on the transition state structures corresponding to proton transfer from the amino to imino form, have been investigated by the B3LYP method in conjunction with 6‐31+G(d,p) and 6‐311+G(3df,2p) basis sets in the gas phase and in solution. The amino form has been found to be the predominant tautomer. The tautomeric barrier heights for water‐ and self‐assisted tautomerization reactions are significantly lower than that from the amino to imino form by the intramolecular proton transfer, showing the catalytic effect of water molecule(s) and the important role of 2‐aminothiazole itself for intermolecular proton transfer. Comparison between the tautomeric barriers demonstrates that the self‐association tautomerization through the dimerization is the most favorable pathway. Bulk solvent effects have been taken into account using the polarizable continuum model (PCM) of water and CCl₄. The polar medium is favorable for the population of the imino form. The amino/imino equilibrium is also analyzed using the aromaticity index nucleus‐independent chemical shift (NICS); the NICS values for the amino form (about ?10 ppm) are more negative than the imino species (about ?8 ppm), showing that the amino form is more stable. The time‐dependent density functional theory (TDDFT) calculations of electronic absorption spectra suggest that the λ_max of dimer is 255 nm. The oscillator strength of the imino forms is less than the amino form, and increases with the polarity of the solvents. All calculations for the tautomerization of 2‐aminothiazole are in reasonable line with the available experiments. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Theoretical investigation of solvent effects on tautomeric equilibrium of 2‐diazo‐4,6‐dinitrophenol

The density functional theory has been used to study the tautomeric equilibrium of 2‐diazo‐4,6‐dinitrophenol(DDNP) in the gas phase and in 14 solvents at the B3LYP/6‐31G* level. The solvent effects on the tautomeric equilibria were investigated by the self‐consistent reaction field theory (SCRF) based on conductor polarized continuum model (CPCM) in apolar and polar solvents and by the hybrid continuum‐discrete model in protic solvent, respectively. Solvent effects on the computed molecular properties, such as molecular geometries, dipole moments, E_LUMO, E_HOMO, total energies for DDNP tautomers and transition state, tautomerization energies and solvation energies have been found to be evident. The tautomeric equilibrium of DDNP is solvent‐dependent to a certain extent. The tautomer I (cyclic azoxy form) is preferred in the gas phase, while in nonpolar solvents tautomer I and II (quinold form) exist in comparable amounts, and in highly polar solvents, the tautomeric equilibrium is shifted in favor of the more polar tautomer II . © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Density Functional Study on the Reactivity of Carbenes Toward 1,2‐H Shifts

The 1,2‐H shift reactions of simple carbenes (CH₂Y‐C‐X) have been studied using density functional theory (DFT). The influence of the substituent X and Y groups on the activation energy (Ea) of 1,2‐H shifts were examined. The ‘by stander’ Y substituents lower E_a in the order of Me, F > Cl, Br > H. Our analysis shows that the X effect is more significant than the by stander Y effect. X substitutions increase E_a of carbenes in the order of F > Cl > Br > Me > H. The influence of X on E_a is governed by the singlet‐triplet energy separation (ΔE_S‐T) of the carbene, i.e., E_a of a carbene is larger as its ΔE_S‐T in creases due to an X substitution. The X effect was also found to be related to the magnitude of the exothermicity: Ea of reaction is smaller when the reaction is more exothermic. Origin of the Y effect is attributed to the inter play between two factors: ‘lateness’ of transition state on the potential energy surface, and the exothermicity of the reaction.     

Metal Derivatives of Heterocyclic Thioamides: Synthesis and Crystal Structures of Copper Complexes with 1‐Methyl‐1,3‐imidazoline‐2‐thione and 1,3‐Imidazoline‐2‐thione

Reactions of copper(I) halides (Cl, Br, I) with 1‐methyl‐1, 3‐imidazoline‐2‐thione (mimzSH) in 1 : 2 molar ratio yielded sulfur‐bridged dinuclear [Cu₂X₂(μ‐S‐mimzSH)₂(η¹‐S‐mimzSH)₂] (X = I, 1 , Br, 2 ; Cl, 3 ) complexes. Copper(I) iodide with 1,3‐imidazoline‐2‐thione (imzSH₂) and Ph₃P in 1 : 1 : 1 molar ratio has also formed a sulfur‐bridged dinuclear [Cu₂I₂(μ‐S‐imzSH₂)₂(PPh₃)₂] ( 4 ) complex. The central Cu(μ‐S)₂Cu cores form parallelograms with unequal Cu–S bond distances {2.324(2), 2.454(3) Å} ( 1 ); {2.3118(6), 2.5098(6) Å} ( 2 ); {2.3075(4), 2.5218(4) Å} ( 3 ); {2.3711(8), 2.4473(8) Å} ( 4 ). The Cu···Cu separations, 2.759–2.877Å in complexes 1 – 3 are much shorter than 3.3446Å in complex 4 . The weak intermolecular interactions {H₂CH···S^# ( 2 ); CH···Cl^# ( 3 ); NH···I^# ( 4 )} between dimeric units in complexes 2 – 4 lead to the formation of linear 1D polymers.     

[DBU‐H]+ and H2o as effective catalyst form for 2,3‐dihydropyrido[2,3‐d]pyrimidin‐4(1H)‐ones: A DFT Study

DFT investigations are carried out to explore the effective catalyst forms of DBU and H₂O and the mechanism for the formation of 2,3‐dihydropyrido[2,3‐d]‐pyrimidin‐4(1H)‐ones. Three main pathways are disclosed under unassisted, water‐catalyzed, DBU and water cocatalyzed conditions, which involves concerted nucleophilic addition and H‐transfer, concerted intramolecular cyclization and H‐transfer, and Dimroth rearrangement to form the product. The results indicated that the DBU and water cocatalyzed pathway is the most favored one as compared to the rest two pathways. The water donates one H to DBU and accepts H from 2‐amino‐nicotinonitrile ( 1 ), forming [DBU‐H]⁺‐H₂O as effective catalyst form in the proton migration transition state rather than [DBU‐H]⁺‐OH^?. The hydrogen bond between [DBU‐H]⁺···H₂O··· 1 ^? decreases the activation barrier of the rate‐determining step. Our calculated results open a new insight for the green catalyst model of DBU‐H₂O. © 2015 Wiley Periodicals, Inc.     

Solid‐state NMR studies of 1,3‐imidazolidine‐2‐selenone and some related compounds

Solid‐state cross‐polarization magic angle spinning ¹³C, ⁷⁷Se and ¹⁵N NMR spectra were recorded for 1,3‐imidazolidine‐2‐selenone, its N‐substituted derivatives and some related compounds. The spinning sideband manifold intensities were used to obtain principal values of ¹³C and ⁷⁷Se chemical shift tensors. Large selenium chemical shift anisotropies were observed for these selenones. Copyright © 2003 John Wiley & Sons, Ltd.     

Pd‐Catalyzed Cycloisomerization of 4‐Aza‐1,6‐enynes to 3‐Aza‐bicyclo[4.1.0]hept‐2‐enes

A method for the synthesis of bicyclo[4.1.0]heptenes from 1,6‐enynes through Pd‐catalyzed cycloisomerization has been developed. N‐ and O‐tethered 1,6‐enynes were successfully transformed to their corresponding 3‐aza‐ and 3‐oxabicyclo[4.1.0]heptenes in reasonable‐to‐high yields using the catalysts [PdCl₂(CH₃CN)₂]/P(OPh)₃ or [Pd(maleimidate)₂(PPh₃)₂] in toluene. The computational calculations using density functional theory indicate that [PdCl₂{P(OPh)₃}] in the oxidation state Pd^II acts as the active catalyst species for the formation of 3‐azabicyclo[4.1.0]heptenes through 6‐endo‐dig cyclization.     

Theoretical Study on the Isomerization Mechanism of Enol Ester from 2-Acyl-1, 3-cyclohexanediones

The present paper employed density function theory to investigate two reaction pathways for isomerization of enol ester proposed by Yang(path a) and the present authors(path a), respectively. The base catalytic effects of solvent triethylamine on these two reactions were also evaluated. It is demonstrated that path B is more preferable than path a due to low barrier height for the rate-determining step.     

Polymerization of (E)‐1,3‐Pentadiene and (E)‐2‐methyl‐1,3‐pentadiene with neodymium catalysts: Examination of the factors that affect the stereoselectivity

(E)‐1,3‐Pentadiene (EP) and (E)‐2‐methyl‐1,3‐pentadiene (2MP) were polymerized to cis‐1,4 polymers with homogeneous and heterogeneous neodymium catalysts to examine the influence of the physical state of the catalyst on the polymerization stereoselectivity. Data on the polymerization of (E)‐1,3‐hexadiene (EH) are also reported. EP and EH gave cis‐1,4 isotactic polymers both with the homogeneous and with the heterogeneous system, whereas 2MP gave an isotactic cis‐1,4 polymer with the heterogeneous catalyst and a syndiotactic cis‐1,4 polymer, never reported earlier, with the homogeneous one. For comparison, the results obtained with the soluble CpTiCl₃‐based catalyst (Cp = cyclopentadienyl), which gives cis‐1,4 isotactic poly(2MP), are examined. A tentative interpretation is given for the mechanism of the formation of the stereoregular polymers obtained and a complete NMR characterization of the cis‐1,4‐syndiotactic poly(2MP) is reported. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3227–3232