Direct palladium-catalyzed C-3 arylation of free (NH)-indoles with aryl bromides under ligandless conditions.
A new method for the efficient, practical, and highly regioselective direct palladium-catalyzed C-3 arylation of free (NH)-indole and its electron-rich 1-unsubstituted derivatives under ligandless conditions is described. The reactions, which are run outside a glovebox without purification of solvent and reagents, involve treatment of free (NH)-indoles with activated, unactivated, and deactivated aryl bromides in refluxing toluene in the presence of K2CO3 as the base and a catalyst system consisting of a combination of Pd(OAc)2 and benzyl(tributyl)ammonium chloride. The experimental results are consistent with a catalytic cycle based on an electrophilic palladation pathway at the 3-position of 1-indolyl potassium salts.
Bellina
Fabio
F
Dipartimento di Chimica e Chimica Industriale, University of Pisa, Via Risorgimento 35, 56125 Pisa, Italy.
Benelli
Francesca
F
Rossi
Renzo
R
D001965:Bromides / Q000737:chemistry*; D002244:Carbon / Q000737:chemistry*; D002384:Catalysis; D006859:Hydrogen / Q000737:chemistry*; D007211:Indoles / Q000138:chemical synthesis* / Q000737:chemistry; D008024:Ligands; D015394:Molecular Structure; D009584:Nitrogen / Q000737:chemistry*; D010165:Palladium / Q000737:chemistry*; D013237:Stereoisomerism
D001965:Bromides; D007211:Indoles; D008024:Ligands; D010165:Palladium; D002244:Carbon; D006859:Hydrogen; C030374:indole; D009584:Nitrogen