Mechanism of Cu/Pd-catalyzed decarboxylative cross-couplings: a DFT investigation.

The reaction mechanism of decarboxylative cross-couplings of benzoates with aryl halides to give biaryls, which is cooperatively catalyzed by copper/palladium systems, was investigated with DFT methods. The geometries and energies of all starting materials, products, intermediates, and transition states of the catalytic cycle were calculated for the two model reactions of potassium 2- and 4-fluorobenzoate with bromobenzene in the presence of a catalyst system consisting of copper(I)/1,10-phenanthroline and the anionic monophosphine palladium complex [Pd(PMe3)Br](-). Several neutral and anionic pathways were compared, and a reasonable catalytic cycle was identified.

[Pd(μ-Br)(P(t)Bu3)]2 as a highly active isomerization catalyst: synthesis of enol esters from allylic esters.

The dimeric Pd(I)-complex [Pd(μ-Br)(P(t)Bu3)]2 was found to be highly active for catalyzing double-bond migration in various substrates such as unsaturated ethers, alcohols, amides, and arenes, under mild conditions. It efficiently mediates the conversion of allylic esters into enol esters, rather than inserting into the allylic C-O bond. The broad applicability of this reaction was demonstrated with the synthesis of 22 functionalized enol esters.

Mechanistic investigation of the Ru-catalyzed hydroamidation of terminal alkynes.

The ruthenium-catalyzed hydroamidation of terminal alkynes has evolved to become a broadly applicable tool for the synthesis of enamides and enimides. Depending on the catalyst system employed, the reaction leads chemo-, regio-, and stereoselectively to a single diastereoisomer. Herein, we present a comprehensive mechanistic study of the ruthenium-catalyzed hydroamidation of terminal alkynes, which includes deuterium-labeling, in situ IR, in situ NMR, and in situ ESI-MS experiments complemented by computational studies.

Synthesis and structure of 2-pyransoylperimidines.

The first examples of 2-pyranosylperimidines are reported. The β-d-glucopyranosyl nitrile oxide 5, generated by base-induced dehydrochlorination of the hydroximoyl chloride 4, reacted with 1,8-diaminonaphthalene to afford the 2-(β-d-glucopyranosyl)perimidine 8. The d-xylo-, d-galacto-, d-manno- and d-glycero analogues 12, 15, 16 and 19 were prepared similarly.

Silver-catalysed protodecarboxylation of carboxylic acids.

A silver-based catalyst system has been discovered that effectively promotes the protodecarboxylation of various carboxylic acids at temperatures of 80-120 degrees C--more than 50 degrees C below those of the best known copper catalysts.