The reaction of imines with alkynes and alkenes, in the presence of 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), to give quinoline derivatives is described. The mechanism of the annulation is discussed, and evidence supporting a non-concerted pathway, at least when the alkene is butyl vinyl ether, is reported. Preliminary information is also given about solid adducts of imines with DDQ, which do
Efficient synthesis of 2,4-disubstituted quinolines: calix[n]arene-catalyzed Povarov-hydrogen-transfer reaction cascade
作者:Juliana Baptista Simões、Ângelo de Fátima、Adão Aparecido Sabino、Luiz Claudio Almeida Barbosa、Sergio Antonio Fernandes
DOI:10.1039/c4ra02036g
日期:——
A new calixarene-catalyzed cascade process, involving Povarov reaction and hydrogen transfer, for the synthesis of 2,4-disubstituted quinolines is described.
Aromatic imines react with phenylacetylene or styrene in an acetonitrile solution of iron(III) chloride to give quinolines 3 or their tetrahydro derivatives 11 together with variable amounts of products 4 arising from the reduction of the imines. The initial step appears to be a one-electron oxidation to generate iron(II) and an imine radical cation. When the reactions are carried out in the presence of stoichiometric amounts of tetrachloro-p-benzoquinone (chloranil), only quinolines 3 are obtained.