DDQ-MEDIATED FORMATION OF CARBON-CARBON BONDS - OXIDATION OF IMINES

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 not seem to be involved in the reaction path leading to quinolines, and should account for the dependence of product yields on the position of substituents on the starting imines.