PALLADIUM- AND/OR COPPER-MEDIATED CROSS-COUPLING REACTIONS BETWEEN 1-ALKYNES AND VINYL, ARYL, 1-ALKYNYL, 1,2-PROPADIENYL, PROPARGYL AND ALLYLIC HALIDES OR RELATED COMPOUNDS. A REVIEW

Sonogashira coupling reactions: Synthesis of 4-substituted-6-methyl-2-(methylthio)pyrimidines catalyzed by Pd–Cu

An efficient method is developed for the synthesis of 4-(3-arylprop-2-ynyloxy)-6-methyl-2-(methylthio)pyrimidines via palladium-catalyzed Sonogashira reactions of 4-methyl-2-(methylthio)-6-(prop-2-yn-1-yloxy)pyrimidine with electron-poor aryl iodides in acetonitrile at room temperature. Excellent yields of the products were obtained in reaction times of 9–11 h.

Design for carbon–carbon bond forming reactions under ambient conditions

The carbon–carbon (C–C) bond forms the ‘backbone’ of nearly every organic molecule, and lies at the heart of the chemical sciences! Let us explore designing of carbon–carbon frameworks at ambient conditions.

Pd-catalyzed one-pot sequential unsymmetrical cross-coupling reactions of aryl/heteroaryl 1,2-dihalides

The present methodology allows the conversion of easily available aryl/heteroaryl 1,2-dihalides into synthetically useful unsymmetrically substituted arenes/heteroarenes in good to excellent yields under mild reaction conditions.

Dendrimer-encapsulated Pd(0) nanoparticles immobilized on nanosilica as a highly active and recyclable catalyst for the copper- and phosphine-free Sonogashira–Hagihara coupling reactions in water

Recyclable dendrimer-encapsulated Pd(0) nanoparticles immobilized on nanosilica in the Sonogashira–Hagihara reaction under copper(i) and phosphine ligand-free conditions in water.

Thermal reactivity of neutral and oxidized ferrocenyl-substituted enediynes

The coupling of two equivalents of ethynylferrocene (2) with one equivalent of 1,2-diiodocyclohexene (1) and 1,2-diiodobenzene (4) using Sonogashira cross-coupling conditions led to 1,2-bis(ferrocenylethynyl)cyclohexene (3) and 1,2-bis(ferrocenylethy-nyl)benzene (5), respectively. At high temperatures enediynes 3 and 5 showed exothermic signals in differential scanning calorimetry (DSC) measurements, suggestive of intramolecular diradicaloid ring formation (Bergman (C1-C6) or Schreiner-Pascal (C1-C5) cyclizations). The oxidation of 3 and 5 to the mono-oxidized enediynes 3+ and 5+ decreased the onset temperatures drastically. Equally, 1-ferrocenylethynyl-2-(p-nitro-phenyl)ethynylbenzene (8) displayed a significant decrease in the onset temperature after oxidation to 8+. Because the insoluble nature of the polymeric material formed in the thermolysis of the oxidized enediynes prevented characterization, the origin of this drastic effect was studied by DFT. Contrary to expectations, one-electron oxidation does not lower the barrier for intramolecular cyclization. Rather, the computations suggest that the polymerization is initiated by a bimolecular process.

Sonogashira coupling in natural product synthesis

This review will focus on selected applications of Sonogashira coupling and subsequent transformations as key steps in the total synthesis of natural products.

Palladium nanoparticles supported on agarose-functionalized magnetic nanoparticles of Fe3O4 as a recyclable catalyst for C–C bond formation via Suzuki–Miyaura, Heck–Mizoroki and Sonogashira–Hagihara coupling reactions

Palladium nanoparticles supported on agarose functionalized Fe₃O₄ catalyzed C–C bond formation reactions.

[Bicyclic furano[2,3-D] derivatives of pyrimidine nucleosides--synthesis and antiviral properties]

The methods of synthesis of furano- and pyrrolo[2,3-dlpyrimidine nucleosides as well as structure activity relationship of obtained compounds towards viruses of varicella zoster, hepatitis C, bovine viral diarrhea and some others are reviewed.

Synthesis of macrolones with central piperazine ring in the linker and its influence on antibacterial activity

Three macrolides, clarithromycin, azithromycin and 11-O-Me-azithromycin have been selected for the construction of a series of new macrolone derivatives. Quinolone-linker intermediates are prepared by Sonogashira-type C(6)-alkynylation of 6-iodoquinolone precursors. The final macrolones, differing by macrolide moiety and substituents at the position N-1 of the quinolone or by the presence of an ethyl ester or free acid on the quinolone unit attached via a linker. The linker comprises of a central piperazine ring bonded to the 4″-O position of cladinose by 3-carbon ester or ether functionality. Modifications of the linker did not improve antibacterial properties compared to the previously reported macrolone compounds. Linker flexibility seems to play an important role for potency against macrolide resistant respiratory pathogens.

Easy access to new heterocyclic systems: 1,4-oxazine and substituted 1,4-oxazines

In the course of our investigations on the synthesis of new nitrogen heterocyclic derivatives, we were interested in the synthesis and study of new 1,4-oxazine rings. To this aim, the desired bisvinylphosphate was prepared from N-Boc morpholine-3,5-dione and was then engaged in palladium-catalyzed reactions (reduction, Suzuki, and Stille cross-coupling reactions). The 1,4-oxazine and its corresponding 3,5-disubstituted derivatives were obtained in fair to good yields and were then functionalized under anionic conditions.

A practical mild, one-pot, regiospecific synthesis of 2,3-disubstituted indoles via consecutive Sonogashira and Cacchi reactions

[Structure: see text] A practical one-pot, regiospecific three-component process for the synthesis of 2,3-disubstituted indoles was developed via consecutive Pd-catalyzed Sonogashira coupling, amidopalladation, and reductive elimination.

4-amino-5-aryl-6-arylethynylpyrimidines: structure-activity relationships of non-nucleoside adenosine kinase inhibitors

A series of non-nucleoside adenosine kinase (AK) inhibitors is reported. These inhibitors originated from the modification of 5-(3-bromophenyl)-7-(6-morpholin-4-ylpyridin-3-yl)pyrido[2,3-d]pyrimidin-4-ylamine (ABT-702). The identification of a linker that would approximate the spatial arrangement found between the pyrimidine ring and the aryl group at C(7) in ABT-702 was a key element in this modification. A search of potential linkers led to the discovery of an acetylene moiety as a suitable scaffold. It was hypothesized that the aryl acetylenes, ABT-702, and adenosine bound to the active site of AK (closed form) in a similar manner with respect to the orientation of the heterocyclic base. Although potent acetylene analogs were discovered based on this assumption, an X-ray crystal structure of 5-(4-dimethylaminophenyl)-6-(6-morpholin-4-ylpyridin-3-ylethynyl)pyrimidin-4-ylamine (16a) revealed a binding orientation contrary to adenosine. In addition, this compound bound tightly to a unique open conformation of AK. The structure-activity relationships and unique ligand orientation and protein conformation are discussed.

Fluorescent 5-Alkynyl-2′-Deoxyuridines: High Emission Efficiency of a Conjugated Perylene Nucleoside in a DNA Duplex

Four fluorescent 5-alkynyl-2'-deoxyuridines were studied in DNA oligonucleotides and their duplexes. The fluorescence response to hybridization differs dramatically for nucleosides containing a perylene fluorochrome either conjugated or not conjugated to the nucleobase. The conjugated nucleoside, 5-(perylen-3-ylethynyl)-2'-deoxyuridine, shows enhanced long-wavelength emission in the DNA duplex, in contrast to the blue fluorescence of perylene on a flexible linker (in 5-[(perylen-3-yl)methoxyprop-1-ynyl]-2'-deoxyuridine), which is quenched upon duplex formation.