The power of two metals: A Pd/Cu catalyst system mediates the in situ formation of acyl nucleophiles by decarboxylation of readily accessible and stable salts of α‐oxocarboxylic acids and their cross‐coupling with aryl or heteroaryl bromides to give ketones. The reaction may be used in the presence of many functional groups and provides good yields.

No abstract

Reaction of 2-mercapto-1-methylimidazole (methimazole) with tris(dimethylamino)borane, B(NMe2)3, provides the tetrahedral dimethylamine adduct of tris(methimazolyl)borane, [(Me2HN)B(methimazolyl)3]. By contrast, imidazole, 2-methylimidazole, 2-chloroimidazole and benzimidazole provide the homoleptic tetra-azolyl systems H[B(azolyl)4], and the same product is obtained even when a substoichiometric quantity of the heterocyle is employed. The change in reaction outcome is correlated with the variation of basic pKa for the heterocycles. A simple acid-base reaction with elimination of HNMe2 is proposed for the reaction with the weakly basic, but more strongly acidic, methimazole. However, for the more strongly basic imidazoles, initial coordination of the heterocycle imine nitrogen to the weakly Lewis acidic boron centre in B(NMe2)3 to form the tetrahedral adduct [(azole)B(NMe2)3] is proposed. The greater availability of the NMe2 lone pairs in this species results in increased basicity and a rapid reaction with further heterocycle to provide the observed H[B(azolyl)4] products. For 2-nitroimidazole, the low basicity (and increased N-H acidity) results in the formation of [(HNMe2)B(2-nitroimidazolyl)3] on reaction with B(NMe2)3, analogous to the product formed with methimazole. Both [(HNMe2)B(methimazolyl)3] and H[B(benzimidazolyl)4] have been structurally characterised by single crystal X-ray crystallography. This chemistry has been exploited to provide a new synthesis of borate-centred tripod ligands, whereby N-methylimidazole is used to activate B(NMe2)3 to reaction with methimazole to form the new ligand [(N-methylimidazole)B(methimazolyl)3] in good yield and a complex of this ligand with Ru(II) has been structurally characterised.

A rational catalyst development based on mechanistic and spectroscopic investigations led to the discovery of a new protocol for catalytic hydroamidation reactions that draws on easily available ruthenium trichloride trihydrate (RuCl 3 ·3 H 2 O) as the catalyst precursor instead of the previously employed, expensive bis(2-methylallyl)(1,5-cyclooctadiene)ruthenium(II). This practical and easy-to-use protocol dramatically improves the synthetic applicability of Ru-catalyzed hydroamidations. The catalyst, generated in situ from rutheniumA C H T U N G T R E N N U N G (III) chloride hydrate, tri-n-butylphosphine, 4-(dimethylamino)-pyridine and potassium carbonate, effectively promotes the addition of secondary amides, lactams and carbamates to terminal alkynes under formation of (E)-anti-Markovnikov enamides. The scope of the new protocol is demonstrated by the synthesis of 24 functionalized enamide derivatives, among them valuable intermediates for organic synthesis.