AbstractFor each step almost equimolar, stoichiometric amounts of substrates are applied.

1,3,4,5-Tetrasubstituted pyrazoles can be rapidly and efficiently synthesized in a one-pot, four-step sequence consisting of Sonogashira coupling, addition-cyclocondensation, bromination, and Suzuki coupling. The second and the last step are microwave-assisted, and according to sequential catalysis, no addition of further Pd catalyst is needed for the terminal step. The title compounds show intense blue fluorescence and high quantum yields.

Development of pincer complex-catalyzed oxidative C-H activation borylation reactions: Synthetic applications and mechanistic studies

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

2,4-Disubstituted benzo[b][1,5]thiazepines represent nonfluorescent intense yellow chromophores and are readily synthesized from acid chlorides, terminal alkynes, and ortho-amino thiophenols by a consecutive one-pot three-component Sonogashira coupling–Michael addition–cyclocondensation sequence under mild conditions in good yields.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Selective C-H Borylation of Alkenes by Palladium Pincer Complex Catalyzed Oxidative Functionalization

A whole family of annelated 4H-thiopyran-4-ones as the core structural unit was readily synthesized in good yields by a microwave-assisted coupling-addition-SNAr (CASNAR) sequence starting from readily available (het)aroyl chlorides, alkynes and sodium sulfide nonahydrate in a consecutive one-pot three-component reaction. All representatives display a pronounced halochromicity of the absorption bands upon protonation. According to DFT calculations, the electronic ground state of the annelated 4H-thiopyran-4-ones possess a considerable zwitterionic character.

2,4-Di- and 2,4,7-trisubstituted quinolines are readily synthesized in a regioselective fashion from acyl chlorides, terminal alkynes, and 2-aminothiophenols by a consecutive, microwave-assisted one-pot three-component Sonogashira coupling-Michael addition-cyclocondensation sequence and following sulfur extrusion in moderate to good yields. The terminal sulfur extrusion step was studied by DFT computations. The absorption spectra of 2,4-disubstituted quinolines can be rationalized by DFT-ZINDO-CI calculations and all derivatives show intense blue emission upon UV excitation.

Alkynones are versatile three-carbon building blocks in heterocyclic chemistry. They are easily and efficiently prepared by a modified Sonogashira coupling of acid chlorides and terminal alkynes. As a consequence of the mild reaction conditions the stage is set for new diversity-oriented routes to heterocycles by sequential and consecutive transformations. Hence, isoxazoles, indolizines, pyrazoles, pyridimines, 1,5-benzoheteroazepines, furans, oxazoles, pyrroles, tetrahydro-beta-carbolines, 4H-thiochromen-4-ones and 4H-thiopyrano[2,3-b]pyridin-4-ones are readily accessible by multicomponent coupling-cycloaddition, coupling-addition-cyclocondensation, or coupling-addition-substitution reactions in a one-pot fashion.

4H-Thiochromen-4-ones and 4H-thiopyrano[2,3-b]pyridin-4-ones are readily synthesized in good yields by a consecutive one-pot, three-component coupling-addition-SNAr (CASNAR) sequence starting from aroyl chlorides, alkynes, and sodium sulfide nonahydrate.

The consecutive Sonogashira coupling of acid chlorides with terminal alkynes, followed by 1,3-dipolar cycloaddition under dielectric heating of in situ generated nitrile oxides from hydroximinoyl chlorides furnishes isoxazoles in moderate to good yields in the sense of a one-pot three-component reaction.

2,4-Disubstituted benzodiazepines are readily synthesized in good yields from acyl chlorides, terminal alkynes, and benzene-1,2-diamines by a consecutive one-pot, three-component Sonogashira coupling/Michael addition/cyclocondensation sequence. These diazepines display intense solid-state fluorescence, but only weak emission in solution at room temperature. The absorption and emission maxima can be controlled by the substitution pattern. Upon cooling, however, the phenomenon of cryofluorescence can be observed. X-ray structure analysis and temperature-dependent NMR indicate that freezing out of conformational interconversions is the source of the thermochromicity observed upon UV excitation. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).

3,5-Disubstituted and 1,3,5-trisubstituted pyrazoles are readily synthesized from acyl chlorides, terminal alkynes, and hydrazines by a consecutive one-pot three-component Sonogashira coupling/Michael addition/cyclocondensation sequence in good to excellent yields. These pyrazoles are highly fluorescent, both in solution and in the solid state. Investigation of the electronic properties by UV/Vis and fluorescence spectroscopy and by DFT and ZINDO Cl computations reveal that the excited state is highly polar and allows fine-tuning of the absorption and emission properties. X-ray structure analyses of 3,5-disubstituted pyrazoles reveal self-organization by hydrogen bonding and pi-stacking. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).

A consecutive coupling-cycloaddition sequence of acid chlorides, terminal alkynes, and in situ generated nitrile oxides furnishes ferrocenyl substituted redox active isoxazoles in moderate to good yields. The structure was unambiguously assigned by X-ray structure analyses and the electronic structure was elucidated by computational methods. Redox potentials of all representatives are strongly effected by the electronic nature of the bridging isoxazoloyl moiety. (C) 2008 Elsevier B. V. All rights reserved.