1,8-二(2-吡咯酰胺)-3,6-二氯咔唑的合成、晶体结构及阴离子识别研究

设计并合成了1,8-二(2-吡咯酰胺)-3,6-二氯咔唑化合物(1), 利用X射线单晶衍射研究了该化合物的固态结构. 利用荧光和紫外-可见光谱技术及¹H NMR滴定法研究了其对阴离子的识别. 研究结果表明, 化合物1对H₂PO₄^-离子有较强的识别能力, 且对H₂PO₄^-离子有明显的荧光增强效应, 可用来识别H₂PO₄^-离子. 同时¹H NMR滴定结果显示, 化合物1在阴离子识别过程中发生了构型转化.     

Ionic liquid-immobilized quinuclidine-catalyzed Morita-Baylis-Hillman reactions

[reaction: see text] The ionic liquid-bound quinuclidine catalyzed Baylis-Hillman reactions were investigated. The IL-supported catalyst showed equally good catalytic activity as compared with its nonimmobilized counterpart. The corresponding Baylis-Hillman adducts were obtained in moderate to high yields in all the cases tested. The IL-supported quinuclidine can be readily recovered and reused six times without significant loss of catalytic activity.     

Ferrocenyl-bearing cyclopseudopeptides as redox-switchable cation receptors

A family of ferrocenyl-bearing cyclopseudopeptides (1-10) designed for redox-switchable receptors of cations was synthesized. Circular dichroism (CD) and cyclic valtammetry (CV) studies of cation binding properties in both the reduced (K1) and oxidized (K2) forms revealed that the binding preference is mainly governed by the charges and radius of the guest cation as well as by the suitability of the host to accommodate the guest. Particularly worth mentioning is the fact that some synthesized cyclopseudopeptides showed high binding affinity and selectivity toward alkaline-earth ions. For example, the K1 of compound 2 binding with Ca2+ is 4.37 x 10(6) mol(-1) x L and its Ca2+/K+ selectivity is 3.1 x 10(5):1, both values are much greater than those of an excellent natural ionophore, valinomycin (1 x 10(5) mol(-1) x L and 0.33:1, respectively). The linear relationship between the shifts of half-wave potentials (deltaE(1/2)) and the radius/charge [r/(+)] ratios suggests that the sensitivity of electrochemical responses to cation complexation be dominated by repulsion factors between the redox center and the incoming cation guest.     

Mechanism and driving force of NO transfer from S-nitrosothiol to cobalt(II) porphyrin: a detailed thermodynamic and kinetic study

The thermodynamics and kinetics of NO transfer from S-nitrosotriphenylmethanethiol (Ph(3)CSNO) to a series of alpha,beta,gamma,delta-tetraphenylporphinatocobalt(II) derivatives [T(G)PPCoII], generating the nitrosyl cobalt atom center adducts [T(G)PPCoIINO], in benzonitrile were investigated using titration calorimetry and stopped-flow UV-vis spectrophotometry, respectively. The estimation of the energy change for each elementary step in the possible NO transfer pathways suggests that the most likely route is a concerted process of the homolytic S-NO bond dissociation and the formation of the Co-NO bond. The kinetic investigation on the NO transfer shows that the second-order rate constants at room temperature cover the range from 0.76 x 10(4) to 4.58 x 10(4) M(-1) s(-1), and the reaction rate was mainly governed by activation enthalpy. Hammett-type linear free-energy analysis indicates that the NO moiety in Ph(3)CSNO is a Lewis acid and the T(G)PPCoII is a Lewis base; the main driving force for the NO transfer is electrostatic charge attraction rather than the spin-spin coupling interaction. The effective charge distribution on the cobalt atom in the cobalt porphyrin at the various stages, the reactant [T(G)PPCoII], the transition-state, and the product [T(G)PPCoIINO], was estimated to show that the cobalt atom carries relative effective positive charges of 2.000 in the reactant [T(G)PPCoII], 2.350 in the transition state, and 2.503 in the product [T(G)PPCoIINO], which indicates that the concerted NO transfer from Ph(3)CSNO to T(G)PPCoII with the release of the Ph(3)CS* radical was actually performed by the initial negative charge (-0.350) transfer from T(G)PPCoII to Ph(3)CSNO to form the transition state and was followed by homolytic S-NO bond dissociation of Ph(3)CSNO with a further negative charge (-0.153) transfer from T(G)PPCoII to the NO group to form the final product T(G)PPCoIINO. It is evident that these important thermodynamic and kinetic results would be helpful in understanding the nature of the interaction between RSNO and metal porphyrins in both chemical and biochemical systems.     

Reactions of the simple nitroalkanes with hydroxide ion in water. Evidence for a complex mechanism

Conventional kinetic analysis of the reactions of nitromethane (NM), nitroethane (NE) and 2-nitropropane (2-NP) with hydroxide ion in water revealed that the reactions are complex and involve kinetically significant intermediates. Kinetic experiments at the isosbestic points where changes in reactant and product absorbance cancel indicate the evolution and decay of absorbance characteristic of the formation of reactive intermediates. The deviations from 1st-order kinetics were observed to increase with increasing extent of reaction and in the reactant order: NM < NE < 2-NP. The apparent deuterium kinetic isotope effects for proton/deuteron transfer approach unity near zero time and increased with time toward plateau values as the reaction kinetics reach steady state. It is proposed that the initially formed preassociation complexes are transformed to more intimate reactant complexes which can give products by two possible pathways.     

Highly enantioselective synthesis of syn-aldols of cyclohexanones via chiral primary amine catalyzed asymmetric transfer aldol reactions in ionic liquid

Chiral primary-tertiary diamine/TfOH was found to catalyze kinetic resolution of racemic syn-aldols of cyclohexanones in ionic liquid effectively, affording the chiral syn-aldols with up to 99:1 syn/anti and 99% ee.     

Chiral biscinchona alkaloid promoted asymmetric allylic alkylation of 3-substituted benzofuran-2(3H)-ones with Morita-Baylis-Hillman carbonates

A highly diastereo- and enantioselective asymmetric allylic alkylation reaction with respect to prochiral 3-substituted benzofuran-2(3H)-ones and MBH carbonate by a chiral biscinchona alkaloid catalyst was investigated. The corresponding adducts, containing a quaternary center at the C3-position of the benzofuran-2(3H)-one as well as a vicinal tertiary center, were generally obtained in high yields (up to 97%) with very good diastereo- (up to 98:2 dr) and enantioselectivities (up to 95% ee).     

1,4-二氢Hantzsch吡啶衍生物的合成及其1H NMR和荧光光谱研究

报道了N-甲基-4-芳基-2,6-二甲基-3,5-二乙酯基-1,4-二氢吡啶(2a-2f),4-芳基-2,6-二苯基-3,5-二乙酯基-1,4-二氢吡啶(3a-3f)及其相应的N-甲基化合物(4a-4f)的合成(芳基p-RC6H4-;R＝OCH3,CH3,H,Cl,CN,NO2).化合物4-芳基-2,6-二甲基-3,5-二乙酯基-1,4-二氢吡啶(1a-1f)可发射较强的荧光,化合物3呈现较弱的荧光,它们的氮甲基产物2和4没有荧光.化合物4氮甲基质子的化学位移值比其相对应的化合物2氮甲基质子的化学位移值向高场移动0.6～0.7.化合物3的4-位次甲基质子的化学位移变化与同碳苯基对位取代基的σ+P有相当好的关联.这些现象反映了化合物2-4的特征构象.