41394-66-5Relevant academic research and scientific papers
Development of decarboxylative coupling processes for the synthesis of azomethines and ketones
Collet, Florence,Song, Bingrui,Rudolphi, Felix,Goossen, Lukas J.
experimental part, p. 6486 - 6501 (2011/12/05)
A bimetallic catalyst system has been developed that allows the synthesis of azomethines by a one-pot three-component decarboxylative coupling, starting from simple, nontoxic precursors, i.e. potassium α-oxo carboxylates, aryl halides and primary amines. In the presence of 15 mol-% copper/phenanthroline and 1 mol-% Pd/dppf, a wide range of valuable imines is conveniently accessible in high yields at 100 °C, an unprecedentedly low temperature for redox-neutral decarboxylative cross-coupling reactions. Hydrogenation of the azomethine products leads to secondary amines. Alternatively, they can be hydrolyzed in situ to aryl ketones. The resulting ketone synthesis via azomethine intermediates is also of interest as it gives higher yields at much lower temperatures than the direct decarboxylative coupling of α-oxo carboxylates with aryl halides. A convenient synthesis of azomethines by a one-pot three-component decarboxylative coupling, starting from potassium α-oxo carboxylates, aryl halides and primary amines is described. Combined with in situ hydrolysis, ketones are obtained. Thisamine-mediated ketone synthesis gives higher yields at lower temperatures than the direct coupling of α-oxo carboxylates. Copyright
Biaryl and aryl ketone synthesis via Pd-catalyzed decarboxylase coupling of carboxylate salts with aryl triflates
Goossen, Lukas J.,Linder, Christophe,Rodriguez, Nuria,Lange, Paul P.
supporting information; experimental part, p. 9336 - 9349 (2010/04/03)
A bimetallic catalyst system has been developed that for the first time allows the decarboxylative crosscoupling of aryl and acyl carboxylates with aryl triflates. In contrast to aryl halides, these electrophiles give rise to non-coordinating anions as byproducts, which do not interfere with the decarboxylation step that leads to the generation of the carbon nucleophilic crosscoupling partner. As a result, the scope of carboxylate substrates usable in this transformation was extended from ortho-substituted or otherwise activated derivatives to a broad range of ortho-, meta-, and para-substituted aromatic carboxylates. Two alternative protocols have been optimized, one involving heating the substrates in the presence of CuI/1,10- phenanthroline (10-15 mol %) and PdI2/phosphine (23 mol%) in NMP for 1-24 h, the other involving CuI/l,10-phenanthroline (615mol%) and PdBr2/Tol-BINAP (2 mol % ) in NMP using microwave heating for 5-10 min. While most products are accessible using standard heating, the use of microwave irradiation was found to be beneficial especially for the conversion of non-activated carboxylates with functionalized aryl triflates. The synthetic utility of the transformation is demonstrated with 48 examples showing the scope and limitations of both protocols. In mechanistic studies, the special role of microwave irradiation is elucidated, and further perspectives of decarboxylase crosscouplings are discussed.
