ChemInform Abstract: Stereoselective Addition of Aliphatic Thiols to Internal Alkynes in a Catalytic System with Palladium “Nanosalt” as an Active Site.
The title complex (1) has been prepared by reaction of ZrCl4 with 1,2,3,4-(tetraphenyl)- cyclopenta-1,3-dienyl lithium (2). The phenyl substituents on the metallocene ligands exert both steric and electronic effects on the active site obtained by activation of 1 with MAO. Thus this catalytic system shows lower polymerization activity than in case of unsubstituted or methyl-substituted ligands and leads to the formation of ethylene oligomers.
We have developed a catalytic system that enables the addition of alcohols to allenes using a combination of 5 mol% Pd(PPh3)4 and 10 mol% benzoic acid. Likewise, the addition reaction of carboxylic acids to alkynes is described. In all cases the reaction proceeded well, giving the corresponding allylation products in good-to-high yields with high regio- and stereoselectivities.Key words: addition, alcohols, carboxylic acids, allenes, alkynes, palladium.
A broad scope catalytic system for the intermolecular addition of carboxylic acids to internal alkynes, in water under mild conditions, has been developed.
A stable and efficient PdCl2(PPh3)2/PEG-400/H2O catalytic system for the hydrophenylation reaction of alkynes has been developed. In the presence of 3 mol% PdCl2(PPh3)2 and 2 equiv. of HOAc, the hydrophenylation of both terminal and internal alkynes with sodium tetraphenylborate proceeded smoothly in a mixture of PEG-400 and water at room temperature or 50 °C to afford a variety of phenyl-substituted alkenes in moderate to high yields. The isolation of the products was easily performed by extraction with petroleum ether, and the PdCl2(PPh3)2/PEG-400/H2O system could be readily recycled and reused six times without apparent loss of catalytic activity.
A novel and ligand-free method was developed for the decarboxylative cross-coupling of alkynylcarboxylic acids with arylboronic acids. By using an environmentally friendly H2O–poly(ethylene glycol) (PEG-400) system as the reaction medium, a series of internal alkynes were synthesized in good yields and with remarkable selectivity. The Pd(OAc)2–H2O–PEG-400 catalytic system could be used for up to three cycles without any loss of activity, demonstrating the robustness of the approach.
Recyclable and reusable PdCl2(PPh3)2/PEG-400/H2O system for the hydrophenylation of alkynes with sodium tetraphenylborate