Hantzsch Ester as a Visible-Light Photoredox Catalyst for Transition-Metal-Free Coupling of Arylhalides and Arylsulfinates

Diethyl 2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate (HEH) has been utilized as a visible-light photoredox catalyst for the cross coupling of arylhalides and arylsulfinates without transition metal, sacrificial agent, and mediator. This method is compatible with various functional groups and provides diaryl sulfones in good to high yields. Mechanistic studies indicate that this reaction undergoes the stepwise light irradiation of HE⁻, single electron transfer (SET) in donor–acceptor complex (DAC) from *HE⁻ to arylhalide, trapping of aryl radical with sulfinate, and SET oxidation of sulfone radical anion by HE^. to sulfone by the DAC method.     

Transition-metal free synthesis of diaryl vinyl selenides: a simple synthetic approach with high selectivity

A simple, highly efficient synthetic protocol is developed for the synthesis of unsymmetrical diaryl vinyl selenides from diaryldiselenide and β-bromo styrene under transition-metal free conditions in N,N′-dimethyl propylene urea and 130 °C to afford high yields and excellent selectivities. This method provides a new strategy to fabricate a wide variety of important substituted molecular skeletons and an alternative to conventionally used metal salts, additives, and ligands.     

Spectroscopic and Crystallographic Characterization of the R3N+−C−H⋅⋅⋅X Interaction

As appreciation for nonclassical hydrogen bonds has progressively increased, so have efforts to characterize these interesting interactions. Whereas several kinds of C−H hydrogen bonds have been well-studied, much less is known about the R₃N⁺−C−H⋅⋅⋅X variety. Herein, we present crystallographic and spectroscopic evidence for the existence of these interactions, with special relevance to Selectfluor chemistry. Of particular note is the propensity for Lewis bases to engage in nonclassical hydrogen bonding over halogen bonding with the electrophilic F atom of Selectfluor. Further, the first examples of ¹H NMR experiments detailing R₃N⁺−C−H⋅⋅⋅X (X=O, N) hydrogen bonds are described.     

Visible‐Light‐Driven Halogen Bond Donor Based Molecular Switches: From Reversible Unwinding to Handedness Inversion in Self‐Organized Soft Helical Superstructures

Visible‐light‐driven molecular switches endowing reversible modulation of the functionalities of self‐organized soft materials are currently highly sought after for fundamental scientific studies and technological applications. Reported herein are the design and synthesis of two novel halogen bond donor based chiral molecular switches that exhibit reversible photoisomerization upon exposure to visible light of different wavelengths. These chiral molecular switches induce photoresponsive helical superstructures, that is, cholesteric liquid crystals, when doped into the commercially available room‐temperature achiral liquid crystal host 5CB, which also acts as a halogen‐bond acceptor. The induced helical superstructure containing the molecular switch with terminal iodo atoms exhibits visible‐light‐driven reversible unwinding, that is, a cholesteric–nematic phase transition. Interestingly, the molecular switch with terminal bromo atoms confers reversible handedness inversion to the helical superstructure upon irradiation with visible light of different wavelengths. This visible‐light‐driven, reversible handedness inversion, enabled by a halogen bond donor molecular switch, is unprecedented.     

Recent Advances in Iodine-Promoted C−S/N−S Bonds Formation

Sulfur-containing scaffold, as a ubiquitous structural motif, has been frequently used in natural products, bioactive chemicals and pharmaceuticals, particularly C−S/N−S bonds are indispensable in many biological important compounds and pharmaceuticals. Development of mild and general methods for C−S/N−S bonds formation has great significance in modern research. Iodine and its derivatives have been recognized as inexpensive, environmentally benign and easy-handled catalysts or reagents to promote the construction of C−S/N−S bonds under mild reaction conditions, with good regioselectivities and broad substrate scope. Especially based on this, several new strategies, such as oxidation relay strategy, have been greatly developed and accelerated the advancement of this field. This review focuses on recent advances in iodine and its derivatives promoted hybridized C−S/N−S bonds formation. The features and mechanisms of corresponding reactions are summarized and the results of some cases are compared with those of previous reports. In addition, the future of this domain is discussed.     

TBAI‐Catalyzed/Water‐Assisted Double C−S Bond Formations: An Efficient Approach to Sulfides through Metal‐Free Three‐Component Reactions

An aqueous catalytic method for double C?S bond formations that involves alcohol derivatives, organic halides, and sodium thiosulfate has been developed. A diverse range of functionalized sulfides, including pharmaceutical and biological derivatives, can be obtained in an efficient and eco‐friendly manner under air. The mechanistic studies revealed that this tetrabutylammonium‐iodide‐catalyzed/water‐assisted reaction generated a mercaptan species as the key intermediate.     

The X-ray crystal structures of three bis(cyclopentadienyl)titanium(IV) derivatives

The X-ray crystal structures of (aqua)bis(cyclopentadienyl)chlorotitanium(IV) trifluoromethanesulfonate, bis(aqua)bis(cyclopentadienyl)titanium(IV) bis(trifluoromethanesul-fonate) and bis(cyclopentadienyl)bis(trifluoromethanesulfonato)titanium(IV) show a pseudo-tetrahedral array of Cp ring centroids and oxygen or oxygen and chloride donors around titanium, and varied long-range packing motifs dependent on the availability of hydrogen bond acceptors within the lattice.     

The structure of 11,12-bis[spiro(cyclopropyl)]-1,4,4a,5,8,8a,9a,10a-octahydro-1,4∶5,8-dimethano-9,10-anthraquinone

In the solid state the 21 Diels-Alder adduct between spiro[4.2]hepta-1,3-diene and p-benzoquinone has a planar cyclohexadione ring with a center of symmetry. Both planar and boat conformations have been observed in similar systems, and the relative stability of the two conformers is of interest. The adduct in the gas phase should contain a mirror plane perpendicular to the cyclohexadione ring; however, a data set collected on a crystal in a capillary resulted in a structure where some bond lengths related by this mirror plane differed by more than 4 in the solid state. Molecular mechanics, MOPAC, and the Cambridge Structural Data Base were used to investigate the factors influencing the conformation of the cyclohexadione ring and the asymmetry across the noncrystallographic mirror plane. The energy differences between the planar and nonplanar ring system is small, and the conformation is determined by crystal packing. No reason for the bond length asymmetry could be found, and a recollection of data on a crystal exposed to the environment led to a structure with statistically equivalent bond lengths.     

肾上腺素与胞嘧啶相互作用的密度泛函理论研究

采用密度泛函理论（DFT）B3LYP方法和6-311＋G（d,p）基组对肾上腺素-胞嘧啶复合物进行结构优化和频率计算,得到15种稳定的复合物.研究发现,所有的复合物进行基组重叠误差（BSSE）校正后的相互作用能为-11.43^-48.96kJ/mol,符合氢键能量范围,相互作用能主要由氢键所贡献.结构和振动频率分析显示,氢键的形成使相应O（N）—H键的键长变长,对称伸缩振动频率减小,说明复合物中形成的氢键都是正常的红移型氢键.应用自然键轨道（NBO）理论和分子中的原子（AIM）理论对15种复合物的氢键性质和特征进行分析,发现氢键对于复合物的稳定性起着重要作用,当复合物形成2个或更多的氢键时,氢键的数目、类型及强度共同决定着复合物的稳定性,复合物基本符合三氢键〉二氢键〉单氢键的稳定顺序,三氢键复合物4是最稳定的,复合物3存在单氢键O—H…O,比部分二氢键复合物要稳定.     

羟甲基功能化吡唑金属羰基化合物的合成及催化性质

研究了3(5)-羟甲基-5(3)-甲基吡唑(L~1),4-羟甲基吡唑(L2)及双(3-羟甲基-5-甲基吡唑)甲烷(L3)与羰基钨(钼)的反应,合成了一系列以单齿及双齿氮配位的羰基金属衍生物LW(CO)5(L=L1或L2)和L3M(CO)4(M=Mo或W)。通过核磁、红外及X射线单晶衍射分析,对这些化合物进行了详细的结构表征。结果表明,这些化合物往往通过O-H…O,N-H…O及O-H…OC-M等氢键作用,形成一维或二维金属有机超分子结构。并且依赖于配体中羟甲基所处的不同位置,这些金属有机超分子表现出明显不同的结构特征。初步的催化活性测试表明,这些新化合物在苯乙炔三聚反应中具有明显的催化活性。