500992-30-3Relevant articles and documents
Synthesis of Indoles by Reductive Cyclization of Nitro Compounds Using Formate Esters as CO Surrogates
Ahmed Fouad, Manar,Ferretti, Francesco,Formenti, Dario,Milani, Fabio,Ragaini, Fabio
, p. 4876 - 4894 (2021/09/20)
Alkyl and aryl formate esters were evaluated as CO sources in the Pd- and Pd/Ru-catalyzed reductive cyclization of 2-nitrostyrenes to give indoles. Whereas the use of alkyl formates requires the presence of a ruthenium catalyst such as Ru3(CO)12, the reaction with phenyl formate can be performed by using a Pd/phenanthroline complex alone. Phenyl formate was found to be the most effective CO source and the desired products were obtained in excellent yields, often higher than those previously reported using pressurized CO. The reaction tolerates many functional groups, including sensitive ones like a free aldehydic group or a pendant pyrrole. Detailed experiments and kinetic studies allow to conclude that the activation of phenyl formate is base-catalyzed and that the metal doesn't play a role in the decarbonylation step. The reactions can be performed in a single thick-walled glass tube with as little as 0.2 mol-% palladium catalyst and even on a 2 g scale. The same protocol can be extended to other nitro compounds, affording different heterocycles.
Ready synthesis of free N-H 2-arylindoles via the copper-catalyzed amination of 2-bromo-arylacetylenes with aqueous ammonia and sequential intramolecular cyclization
Wang, Huifeng,Li, Yaming,Jiang, Linlin,Zhang, Rong,Jin, Kun,Zhao, Defeng,Duan, Chunying
, p. 4983 - 4986 (2011/08/05)
A wide range of free N-H 2-arylindoles were synthesised via the copper(ii)-catalyzed amination of 2-bromo-arylacetylenes with aqueous ammonia and sequential intramolecular cyclization. The convenience and atom economy of aqueous ammonia, and the low cost of the copper catalytic system make this protocol readily superior in practical application. The Royal Society of Chemistry 2011.
Iron-palladium association in the preparation of indoles and one-pot synthesis of bis(indolyl)methanes
Terrasson, Vincent,Michaux, Julien,Gaucher, Anne,Wehbe, Johny,Marque, Sylvain,Prim, Damien,Campagne, Jean-Marc
, p. 5332 - 5335 (2008/03/14)
Indoles were prepared by annulation of the parent alkynylanilines with the use of a new FeCl3-PdCl2 catalytic combination. High yields were obtained by using low loadings of the transition-metal complex (FeCl3-PdCl2: 2 and 1 mol-%, respectively). One-pot accesses to bis(indolyl)methanes and trisubstituted indoles through annulation/Friedel-Crafts alkylation and annulation/1,4-Michael addition sequences, in which FeCl3 acts both as a cooxidant and a Lewis acid are described. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.