Scale Effect of a Fluorescent Waveguide in Organic Micromaterials: A Case Study Based on Coumarin Microfibers.

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.

Pd-catalyzed cascade reactions involving skipped dienes: from double carbopalladation to remote C-C cleavage.

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 β-C-elimination process which does not rely on the use of strained or sterically hindered substrates.

Ruthenium-catalyzed cascade C-H functionalization of phenylacetophenones.

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.

S-, N-, and Se-difluoromethylation using sodium chlorodifluoroacetate.

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.

Transition metal-catalyzed C-C bond formation via C-S bond cleavage: an overview.

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.

Synthesis and HIV-1 RT inhibitory action of novel (4/6-substituted benzo[d]thiazol -2-yl)thiazolidin-4-ones. Divergence from the non-competitive inhibition mechanism.

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.

Microwave-assisted C-C bond forming cross-coupling reactions: an overview.

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.

N-heterocyclic carbene catalyzed aroylation of 3,5-dichloro-2(1H)-pyrazinones.

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.

A microwave-assisted diastereoselective multicomponent reaction to access dibenzo[c,e]azepinones: synthesis and biological evaluation.

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.

An expeditious route toward pyrazine-containing nucleoside analogues.

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.

Diversity-oriented synthesis of dibenzoazocines and dibenzoazepines via a microwave-assisted intramolecular A(3)-coupling reaction.

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.

Microwave-assisted cycloaddition reactions.

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.

Microwave-assisted synthesis of a novel class of imidazolylthiazolidin-4-ones and evaluation of its biological activities.

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.

Microwave-assisted palladium-catalyzed phosphonium coupling of 2(1H)-pyrazinones.

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.

Mild room-temperature palladium-catalyzed C3-arylation of 2(1H)-pyrazinones via a desulfitative Kumada-type cross-coupling reaction.

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.

Synthesis and fungicidal activity of 3,5-dichloropyrazin-2(1H)-one derivatives.

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.

Diversity oriented microwave-assisted synthesis of (-)-steganacin aza-analogues.

A novel microwave-assisted, highly efficient protocol for the synthesis of hitherto unknown aza-analogues of (-)-Steganacin, a naturally occurring bisbenzocyclooctadiene lignan lactone with potent antileukemic and tubulin polymerization inhibitory activity, has been developed. Focused microwave irradiation is demonstrated to be highly beneficial in promoting the three crucial steps of the sequence to effect the final ring closure: the Suzuki-Miyaura reaction, Cu-mediated A3-coupling, as well as the intramolecular Huisgen 1,3-dipolar cycloaddition.

A novel and versatile entry to asymmetrically substituted pyrazines.

A novel and convenient procedure for the synthesis of asymmetrically tri- and tetrasubstituted pyrazines starting from para-methoxybenzyl-protected 3,5-dichloro-2(1H)-pyrazinones was elaborated. The key step is the conversion of the intermediate para-methoxybenzyl-protected thiopyrazinone upon treatment with MeI/I(2), into a pyrazine, rendering the chlorine in the C5-position susceptible to substitution. This approach entails the orthogonal introduction of the four substituents of the pyrazine scaffold.

The first palladium-catalyzed desulfitative Sonogashira-type cross-coupling of (hetero)aryl thioethers with terminal alkynes.

An unprecedented desulfitative Sonogashira-type cross-coupling protocol is exemplified by the synthesis of substituted 5-chloro-3-alkynylpyrazinones from the corresponding 5-chloro-3-(phenylsulfanyl) pyrazin-2(1H)-ones. The applicability of the method is extended to solid-phase linked pyrazin-2(1H)-ones as well as to some oxazinones, pyrazines, and phenyl thioesters.

Palladium-catalyzed copper(I)-mediated cross-coupling of arylboronic acids and 2(1H)-pyrazinones facilitated by microwave irradiation with simultaneous cooling.

The application of a palladium-catalyzed Cu(I)-mediated Liebeskind-Srogl protocol for the decoration of the 2(1H)-pyrazinone scaffold resulted in significantly improved yields and rates when performed under microwave irradiation with simultaneous cooling.