ABSTRACT
The classical method for evaluating the waveguide ability only focuses on the optical loss coefficient. However, for the micro- or submicroscale, an organic waveguide is demonstrated by the present study whose scale effect should not be neglected. We found that the optical loss coefficient increased remarkably when decreasing the sectional size of the microfibers. Furthermore, simulations based on Finite-Difference Time-Domain also demonstrated the size-dependent effect of the waveguide. Both the experimental and simulating results showed that the optical loss coefficient converges to a certain value, which means that the scale effect can be neglected as the sectional size is large enough. On the basis of the present study, we suggest that the scale-dependent effect on the sectional size of the waveguide should be investigated by evaluating the waveguide ability by the optical loss coefficient.
Subject(s)
Coumarins/radiation effects , ortho-Aminobenzoates/radiation effects , Coumarins/chemistry , Crystallization , Fluorescence , Light , Manufactured Materials/radiation effects , Spectroscopy, Fourier Transform Infrared , Static Electricity , X-Ray Diffraction , ortho-Aminobenzoates/chemistryABSTRACT
We report two ligand-controlled cascade reactions relying on the intramolecular carbopalladation of skipped dienes. The use of a bulky monodentate phosphine ligand affords [4,5]-spirocycles via sequential double carbopalladation, however bidentate phosphines promote a remote ß-C-elimination process which does not rely on the use of strained or sterically hindered substrates.
ABSTRACT
Three orthogonal cascade CH functionalization processes are described, based on ruthenium-catalyzed CH alkenylation. 1-Indanones, indeno indenes, and indeno furanones were accessed through cascade pathways by using arylacetophenones as substrates under conditions of catalytic [{Ru(p-cymene)Cl2 }2 ] and stoichiometric Cu(OAc)2 . Each transformation uses CH functionalization methods to form CC bonds sequentially, with the indeno furanone synthesis featuring a CO bond formation as the terminating step. This work demonstrates the power of ruthenium-catalyzed alkenylation as a platform reaction to develop more complex transformations, with multiple CH functionalization steps taking place in a single operation to access novel carbocyclic structures.
ABSTRACT
A simple protocol for the difluoromethylation of thiols is reported using chlorodifluoroacetate as the difluoromethylating agent. This cheap reagent undergoes smooth decarboxylation at 95 °C to afford difluorocarbene, which can be trapped with a variety of aromatic and heteroaromatic thiols. The reaction is also effective for the difluoromethylation of heterocyclic nitrogen compounds and phenylselenol.
ABSTRACT
Transition metal-catalyzed C-C bond formations have been well studied over the last four decades. An improved mechanistic understanding of such reactions has helped chemists to develop further improvements, modifications and even new reactions. In the area of transition metal-catalyzed cross-coupling reactions the C-S bond cleaving reactions have attracted a lot of attention in the last decade as they provide a good alternative to the use of organo-halide reagents in traditional cross-coupling reactions. The availability of a wide range of organo-sulfur species provides the opportunity for developing different transformations for the synthesis of interesting organic compounds. This tutorial review focuses on recent examples of the transition metal-catalyzed C-C bond forming reactions using organo-sulfur species.
ABSTRACT
Reverse transcriptase (RT) inhibitors play a major role in the therapy of human immunodeficiency virus type 1 (HIV-1) infection. Although, many compounds are already used as anti-HIV drugs, research on development of novel inhibitors continues, since drug resistant strains appear because of prolonged therapy. In this paper, we present the synthesis and evaluation of HIV-1 RT inhibitory action of eighteen novel (4/6-halogen/MeO/EtO-substituted benzo[d]thiazol-2-yl)thiazolidin-4-ones. The two more active compounds (IC50 : 0.04 µM and 0.25 µM) exhibited better inhibitory action than the reference compound, nevirapine. Docking analysis supports a stable binding of the most active derivative to the allosteric centre of RT. Kinetic analysis of two of the most active compounds indicate an uncompetitive inhibition mode. This is a desired characteristic, since mutations that affect activity of traditional non-competitive NNRTIs may not affect activity of compounds of this series. Interestingly, the less active derivatives (IC50 > 40 µM) exhibit a competitive mode of action.
Subject(s)
HIV Reverse Transcriptase/antagonists & inhibitors , Reverse Transcriptase Inhibitors/chemical synthesis , Reverse Transcriptase Inhibitors/pharmacology , Chemistry Techniques, Synthetic , Drug Evaluation, Preclinical/methods , HIV Reverse Transcriptase/chemistry , HIV Reverse Transcriptase/metabolism , Inhibitory Concentration 50 , Kinetics , Molecular Docking Simulation , Nevirapine/pharmacology , Nitriles , Pyridazines/chemistry , Pyridazines/metabolism , Pyrimidines , Reverse Transcriptase Inhibitors/chemistry , Structure-Activity Relationship , Thiazolidines/chemistry , Toxicity TestsABSTRACT
Among the fundamental transformations in the field of synthetic organic chemistry, transition-metal-catalyzed reactions provide some of the most attractive methodologies for the formation of C-C and C-heteroatom bonds. As a result, the application of these reactions has increased tremendously during the past decades and cross-coupling reactions became a standard tool for synthetic organic chemists. Furthermore, a tremendous upsurge in the development of new catalysts and ligands, as well as an increased understanding of the mechanisms, has contributed substantially to recent advances in the field. Traditionally, organic reactions are carried out by conductive heating with an external heat source (for example, an oil bath). However, the application of microwave irradiation is a steadily gaining field as an alternative heating mode since its dawn at the end of the last century. This tutorial review focuses on some of the recent developments in the field of cross-coupling reactions assisted by microwave irradiation.
ABSTRACT
An unprecedented microwave-assisted multicomponent strategy has been elaborated for the fast, efficient, and diastereoselective generation of the dibenzo[c,e]azepinone scaffold. The generated compounds were evaluated for their bioactivity.
Subject(s)
Antineoplastic Agents/chemical synthesis , Azepines/chemical synthesis , Benzoates/chemistry , Combinatorial Chemistry Techniques , Enzyme Inhibitors/chemical synthesis , Aldehydes/chemistry , Amyloid Precursor Protein Secretases/antagonists & inhibitors , Amyloid Precursor Protein Secretases/metabolism , Animals , Antineoplastic Agents/pharmacology , Azepines/pharmacology , Carboxylic Acids/chemistry , Catalysis , Cell Line, Tumor , Enzyme Inhibitors/pharmacology , Female , Friend murine leukemia virus , Humans , Leukemia, Erythroblastic, Acute/drug therapy , Mammary Neoplasms, Animal/drug therapy , Mice , Microwaves , Molecular Structure , Stereoisomerism , Uterine Cervical Neoplasms/drug therapyABSTRACT
The N-heterocyclic carbene catalyzed chemoselective C3-aroylation of 3,5-dichloro-2(1H)-pyrazinones with various aldehydes is reported. We herein describe results of this remarkable mild and efficient procedure.
Subject(s)
Biological Products/chemical synthesis , Pyrazines/chemical synthesis , Aldehydes/chemistry , Catalysis , Heterocyclic Compounds/chemistry , Methane/analogs & derivatives , Methane/chemistry , Molecular Structure , StereoisomerismABSTRACT
An improved and convenient methodology for the synthesis of asymmetrically substituted pyrazines starting from 3,5-dichloropyrazin-2(1H)-ones has been elaborated. Several nucleoside analogues have been synthesized containing the pyrazine core as the organic base coupled with the sugar via a triazole linkage. The beneficial effect of microwave irradiation throughout the sequence has been demonstrated.
Subject(s)
Nucleosides/chemistry , Nucleosides/chemical synthesis , Pyrazines/chemistry , Pyrazines/chemical synthesis , Triazoles/chemistry , Base Sequence , Magnetic Resonance Spectroscopy , Microwaves , Molecular StructureABSTRACT
An unprecedented, diversity-oriented strategy for the generation of 6,7-dihydro-5H-dibenzo[c,e]azepines and 5,6,7,8-tetrahydrodibenzo[c,e]azocines by a microwave-assisted copper-catalyzed intramolecular A(3)-coupling reaction is presented.
Subject(s)
Azepines/chemical synthesis , Azocines/chemical synthesis , Bromides/chemistry , Copper/chemistry , Microwaves , Azepines/chemistry , Azocines/chemistry , Catalysis , Molecular StructureABSTRACT
Cycloaddition reactions belong to one of the most well-investigated and widely used reactions in synthetic organic chemistry for the construction of (hetero)cyclic compounds in a single-step operation. In this tutorial review, a select number of examples of some [3+2] cycloadditions, i.e. for 1,2,3-triazole formation, as well as of some [4+2] and [2+2] cycloadditions are reviewed, where it has been proven that the application of microwave irradiation has a profound influence on the outcome of the reaction.
ABSTRACT
The synthesis and biological activity of a hitherto unknown class of compounds, the imidazolylthiazolidin-4-ones, are described. A two-step procedure has been elaborated starting from our previously described 2-aminoimidazoles. The application of microwave irradiation has been proven to be beneficial for the condensation of the imine with mercaptoacetic acid leading to the formation of imidazolylthiazolidin-4-ones. None of the compounds showed antiviral activity at subtoxic concentrations. Several compounds displayed a moderate cytostatic activity. These data form the basis for further improvement of the potential antiproliferative activity of this class of compounds.
Subject(s)
Chemistry, Pharmaceutical/methods , Microwaves , Thiazolidinediones/chemistry , Thiazolidinediones/chemical synthesis , Thiazolidinediones/pharmacology , Animals , Catalysis/radiation effects , Cell Line, Tumor , Cell Proliferation/drug effects , Chemistry, Organic/methods , Humans , Imidazoles/chemistry , Mice , Microbial Sensitivity Tests , Models, Biological , Models, Molecular , Molecular ConformationABSTRACT
An expedient route for the synthesis of differently substituted 2(1H)-pyrazinones applying a microwave-assisted palladium-catalyzed phosphonium coupling procedure is reported. The method has also been successfully extended to some other tautomerizable heterocycles for efficient C-C cross-coupling.
ABSTRACT
An efficient desulfitative Kumada-type cross-coupling protocol is reported for the C3-arylation of 5-chloro-3-(phenylsulfanyl)pyrazin-2(1H)-ones. The method has also been successfully extended to the arylation of some (hetero)aryl thioethers and thioesters.
ABSTRACT
We synthesized a family of 3,5-dichloropyrazin-2(1H)-one derivatives and assessed their in vitro fungicidal activity against Candida albicans. Compounds 11 and 20 were most active against C. albicans and induced accumulation of reactive oxygen species in this pathogen. Using a genome-wide approach in the yeast Saccharomyces cerevisiae, we demonstrated that genes involved in vacuolar functionality and DNA-related functions play an important role in cellular mechanisms underlying the fungicidal activity of these compounds.
