Cu-catalyzed decarboxylative coupling of propiolic acids with boronic acids

Phenylpropiolic acid isolated in cryogenic nitrogen and xenon matrices: NIR and UV-induced study

Phenylpropiolic acid (C6H5C≡CCOOH, PPA) isolated in nitrogen and xenon cryogenic matrices was studied by infrared spectroscopy. The experimental studies were complemented by a series of quantum chemical calculations carried out at the density functional theory (B3LYP) and MP2 levels of theory (with different basis sets). The calculations predicted the existence of two planar PPA conformers, differing in the arrangement of the carboxylic group. The higher-energy trans-PPA conformer has a negligible population in the gas phase at room temperature and was prepared in situ in the N2 cryomatrix through vibrationally-induced rotamerization of the lower-energy cis-PPA conformer, achieved using selective narrowband infrared excitation of the OH stretching coordinate of the latter species. Broadband UV (λ > 235 nm) irradiation of matrix-isolated cis-PPA was also undertaken, leading to the observation of cis-PPA → trans-PPA isomerization. No other UV-induced photoreactions were observed. The in situ generated trans-PPA conformer was found to decay back to cis-PPA in the dark by tunneling, and its lifetimes under different experimental conditions were determined. The assignment of the infrared spectra of both conformers is presented, considerably extending the vibrational information available on this molecule.

ICl/AgNO3 Co-Catalyzed Radical Oxidation of Diaryl- and Alkylarylalkynes into 1,2-Diketones

A novel ICl/AgNO3 co-catalyzed radical oxidation of diaryl- and alkylarylalkynes into 1,2-diketones is reported. The reaction proceeded smoothly under mild conditions and generated 1,2-diketones in moderate to good yields with a good tolerance of functional groups. Furthermore, the obtained C4-(1,2-diketoaryl)isoxazoles could react smoothly with 1,2-diaminobenzene to form C4-(3-arylquinoxalin-2-yl)isoxazoles. At last, a new one-pot strategy for the synthesis of quinoxalines from 1,2-diphenylethynes and 1,2-diaminobenzene is also reported.

Copper and silver benzoate and aryl complexes and their implications for oxidative decarboxylative coupling reactions

A copper(ii) benzoate complex is a viable intermediate for copper-catalyzed oxidative decarboxylative coupling reactions.

“Anti-Michael addition” of Grignard reagents to sulfonylacetylenes: synthesis of alkynes

The addition of Grignard reagents to arylsulfonylacetylenes, which undergoes an “anti-Michael addition”, resulting in their alkynylation under very mild conditions is described.

Pd(NHC)PEPPSI-diazonium salts: an efficient blend for the decarboxylative Sonogashira cross coupling reaction

Pd(NHC) complexes catalyzed the synthesis of symmetrical and unsymmetrical internal alkynes with a broad spectrum of substrates that includes aromatic and heteroaromatic diazonium salts.

Functionalized α,β-ynones: efficient ligand for Cu catalyzed Sonogashira-type cross-coupling reaction

1,3-Yones as σ-, π-electron donating ligands significantly accelerated the cross-coupling reactions of aryl iodides with terminal alkynes, in which as low as 0.1 to 1 mol% of CuI were efficiently activated.

Copper-catalyzed aerobic decarboxylative sulfonylation of cinnamic acids with sodium sulfinates: stereospecific synthesis of (E)-alkenyl sulfones

A copper-catalyzed aerobic decarboxylative sulfonylation of alkenyl carboxylic acids with sodium sulfinates is developed. This study offers a new and expedient strategy for stereoselective synthesis of (E)-alkenyl sulfones that are widely present in biologically active natural products and therapeutic agents. Moreover, the transformation is proposed to proceed via a radical process and exhibits a broad substrate scope and good functional group tolerance.