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排序方式: 共有257条查询结果,搜索用时 78 毫秒
1.
Shixiong Chen Xiaotian Zhao Ming Jin Wanqiu Huang Guodong Ye Haiyan Pan Decheng Wan 《Journal of polymer science. Part A, Polymer chemistry》2021,59(17):1899-1911
Four 1,5-diphenyl-3-aromatic heterocyclyl-2-pyrazoline-based sulfonium salt photoacid generators (PAGs) with different aromatic heterocycles substituted on C3 atom and dimethyl sulfonium group on C5 atom were synthesized. These PAGs were highly photosensitive in the 365–425 nm light-emitting diode region, and the intramolecular charge transfer from the pyrazoline ring to sulfonium salts induced efficient photolysis and high ΦH+. The heterocycles as well as their substituted positions significantly influenced the energy of the S2 orbital, which was determined by the electrochemical and absorption properties of the PAGs. The raising of the S2 orbital energy enlarged the energy gap of S0–S2 and S1–S2, resulting in blue shift of the absorption spectra and increase in the quantum yield of photoacid generation (ΦH+), respectively. When the energy of excited electrons was higher than that of the S2 orbital, the transition from S0 to S2 (π–π*) occurred before the C-S cleavage on S1 and the PAGs showed high ΦH+ values (0.52–0.72). The transition from S0 to S1 (π–σ*) occurred when the energy of electrons is lower than that of the S2 orbital, and the PAGs showed low ΦH+ value. The photopolymerization kinetics demonstrated that these PAGs were highly efficient cationic photoinitiators. 相似文献
2.
Martin Sweeney Darren Conboy Styliana I. Mirallai Fawaz Aldabbagh 《Molecules (Basel, Switzerland)》2021,26(9)
This review article provides a perspective on the synthesis of alicyclic and heterocyclic ring-fused benzimidazoles, imidazo[4,5-f]benzimidazoles, and imidazo[5,4-f]benzimidazoles. These heterocycles have a plethora of biological activities with the iminoquinone and quinone derivatives displaying potent bioreductive antitumor activity. Synthesis is categorized according to the cyclization reaction and mechanisms are detailed. Nitrobenzene reduction, cyclization of aryl amidines, lactams and isothiocyanates are described. Protocols include condensation, cross-dehydrogenative coupling with transition metal catalysis, annulation onto benzimidazole, often using CuI-catalysis, and radical cyclization with homolytic aromatic substitution. Many oxidative transformations are under metal-free conditions, including using thermal, photochemical, and electrochemical methods. Syntheses of diazole analogues of mitomycin C derivatives are described. Traditional oxidations of o-(cycloamino)anilines using peroxides in acid via the t-amino effect remain popular. 相似文献
3.
Qiuyu He Lirong Cao Yiran Wei Prof. Gregory R. Dake 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(42):e202201328
The utility of 2-diphenylphosphoryloxy-1,3-dienes for the construction of substituted six-membered nitrogen heterocycles is presented. These dienes undergo boron trifluoride-promoted aza-Diels–Alder reactions when reacted with imines or related species formed in situ using aldehydes and amine derivatives. The stability of the dienes allows this three-component reaction to be carried out with no special precautions to eliminate water or air. Thirty-one examples of this process are presented. The usefulness of the enol phosphate functional group is highlighted in further reactions after the cycloaddition step to generate functionalized piperidenes or pyridines. 相似文献
4.
Evan A. Sarina Marilyn M. Olmstead Divya Kanichar Michael P. Groziak 《Acta Crystallographica. Section C, Structural Chemistry》2015,71(12):1085-1088
2‐Acylated 2,3,1‐benzodiazaborines can display unusual structures and reactivities. The crystal structure analysis of the boron heterocycle obtained by condensing 2‐formylphenylboronic acid and picolinohydrazide reveals it to be an N→B‐chelated zwitterionic tetracycle (systematic name: 1‐hydroxy‐11‐oxo‐9,10,17λ5‐triaza‐1λ4‐boratetracyclo[8.7.0.02,7.012,17]heptadeca‐3,5,7,12,14,16‐hexaen‐17‐ylium‐1‐uide), C13H10BN3O2, produced by the intramolecular addition of the Lewis basic picolinoyl N atom of 1‐hydroxy‐2‐(pyridin‐2‐ylcarbonyl)benzo[d][1,2,3]diazaborinine to the boron heterocycle B atom acting as a Lewis acid. Neither of the other two pyridinylcarbonyl isomers (viz. nicotinoyl and isonicotinoyl) are able to adopt such a structure for geometric reasons. A favored yet reversible chelation equilibrium provides an explanation for the slow D2O exchange observed for the OH resonance in the 1H NMR spectrum, as well as for its unusual upfield chemical shift. Deuterium exchange may take place solely in the minor open (unchelated) species present in solution. 相似文献
5.
Multicomponent reactions (MCRs) have inherent advantages in pot, atom, and step economy (PASE). This important green synthetic approach has gained increasing attention due to high efficiency, minimal waste, saving resources, and straightforward procedures. Presented in this review article are the recent development on 5-compoment reactions (5CRs) of the following six types: (I) five different molecules A + B + C + D + E; pseudo-5CRs including (II) 2A + B + C + D, (III) 2A + 2B + C, (IV) 3A + B + C, (V) 3A + 2B, and (VI) 4A + B. 5CRs with more than five-reaction centers are also included. 相似文献
6.
Bao‐Hua Zhang Lan‐xiang Shi Si‐Jie Liu Rui‐Xia Guo 《Journal of heterocyclic chemistry》2015,52(4):1234-1239
An efficient copper‐catalyzed N‐arylation reactions of imidazole, indole, and triazole with aryl or heteroaryl halides using cyclen derivatives as efficient organic base and ligand at moderate temperature have been investigated. The cross‐couplings proceed smoothly with good to excellent yields. 相似文献
7.
Corina Cheptea Valeriu Sunel Shardi Manahedji Ardeshir Ana Cezarina Morosanu 《Molecular Crystals and Liquid Crystals》2020,697(1):97-107
AbstractDipeptide derivatives from p-aminobenzoyl-phenylglycine and p-aminobenzoyl-phenylalanine were grafted on 1,2,4-triazole heterocycle in order to get new substances with potential biological activity. The compounds synthetized and characterized in this paper have a structure that fits in the antimetabolites category, products used to treat malignant tumors. The presence of several bioactive groups in the same molecule permits us to study the chemical structure - biological activity correlation based on computational analyses using SPARTAN’14 software. Some correlations between the molecular parameters established with Spartan’14 software are evidenced in this paper. 相似文献
8.
9.
Dr. Liangliang Song Prof. Dr. Erik V. Van der Eycken 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(1):121-144
Polycycles are abundantly present in numerous advanced chemicals, functional materials, bioactive molecules and natural products. However, the strategies for the synthesis of polycycles are limited to classical reactions and transition metal-catalyzed cross-coupling reactions, requiring pre-functionalized starting materials and lengthy synthetic operations. The emergence of novel approaches shows great promise for the fields of organic/medicinal/materials chemistry. Among them, transition metal-catalyzed C−H activation followed by intermolecular annulation reactions prevail, due to their straightforward manner with high atom- and step-economy, providing rapid, concise and efficient methods for the construction of diverse polycycles. Several strategies have been developed for the synthesis of polycycles, relying on sequential multiple C−H activation/annulation, or combination of C−H activation/annulation and further interaction with a proximal group, or merger of C−H activation with a cycloaddition reaction, or in situ formation of the directing group. These are attractive, efficient, step- and atom-economic methods starting from commercially available materials. This Minireview will provide an introduction to transition metal-catalyzed C−H activation for the synthesis of polycycles, helping researchers to discover indirect connections and reveal hidden opportunities. It will also promote the discovery of novel synthetic strategies relying on C−H activation. 相似文献
10.