38982-12-6Relevant articles and documents
Heck Reactions of Acrolein or Enones and Aryl Bromides – Synthesis of 3-Aryl Propenals or Propenones and Consecutive Application in Multicomponent Pyrazole Syntheses
Stephan, Marvin,Panther, Jesco,Wilbert, Fabio,Ozog, Pauline,Müller, Thomas J. J.
supporting information, p. 2086 - 2092 (2020/03/23)
3-(Hetero)aryl propenals or propenones are efficiently prepared by a Heck reaction of (hetero)aryl bromides and acrolein or vinyl ketones using Beller's CataCXium Ptb ligand under Jeffery's and Fu's conditions. The formation of these three-carbon building blocks is embedded into consecutive three- and pseudo-four-component syntheses of 3-(hetero)aryl and 3,5-diarylpyrazoles with a broad substitution pattern in moderate to excellent yield.
Heck arylation of acrolein acetals using the 9-bromoanthracene: A case of study
Pan, Ke,No?l, Sébastien,Pinel, Catherine,Djakovitch, Laurent
, p. 2863 - 2868 (2008/12/21)
The influence of several parameters on the selectivity of the palladium catalysed Heck coupling of 9-bromoanthracene with acrolein acetals was studied. While the ester is the quasi exclusive product when only a base (i.e. NaOAc, K2CO3, etc.) is added in the medium, the presence of halide abstracting agent such as thallium or silver salts decreases noticeably the selectivity towards the ester. On the other hand, the addition of n-Bu4NOAc yields to the formation of the aldehyde with up to 74% selectivity. The presence of water was found to play a significant role not only on the rate but also on the selectivity of the reaction. A comprehensive mechanism is proposed outlining the influence of each additive, particularly on the selectivity of the reaction.
Efficient heterogeneously palladium-catalysed heck arylation of acrolein diethyl acetal. Selective synthesis of cinnamaldehydes or 3-arylpropionic esters
Noel, Sebastien,Luo, Ciahong,Pinel, Catherine,Djakovitch, Laurent
, p. 1128 - 1140 (2008/03/27)
A heterogeneous tetrakis(ammine)palladium-NaY zeolite {[Pd(NH 3)4]/NaY] catalyst was applied successfully to the Heck arylation of acrolein diethyl acetal using a large variety of aryl and heteroaryl bromides. Depending on the reaction conditions (Heck versus Cacchi) good to high selectivities toward the 3-arylpropionic esters or to the cinnamaldehydes were achieved, respectively. Under classical Heck conditions, while the catalyst was found to be stable over the two first runs, it showed significant loss of activity from the third cycle. Under Cacchi conditions, the catalyst could not be reused as it led to high dehalogenation rates. All results indicate that the reactions proceed through dissolved palladium species in the bulk solution (leaching). As observed by transmission electronic microscopic (TEM) analyses, while these species can be trapped and stabilised by the zeolite framework under the Heck conditions, they tend to form large palladium(0) aggregates under the Cacchi conditions leading to dehalogenation rather than to the expected Heck coupling.
