Thermal Cyclodimerization of Aliphatic Secondary C,N-Dilithioallylamine Derivatives.
beta-Nitrogen-functionalized vinylic organolithium compounds derived from secondary aliphatic allylamines have been found to undergo upon heating (reflux of THF) either a dimerization or a regio- and stereoselective cyclodimerization reaction affording diamino 1,4-dienes or cis-2,3-disubstituted 4-methylenepyrrolidines, respectively, according to reaction time. In contrast, the corresponding dianions derived from aromatic allylamines underwent protonation by the solvent under analogous thermal treatment. A mechanism accounting for all these results has been proposed, which involves a spontaneous beta-elimination of lithium hydride and an intramolecular nucleophilic cyclization by addition of a lithium amide to an alkene group as critical steps. In addition, experimental evidence is provided about the formation of 3-lithio-1-aza 1,3-dienes as intermediates in these unusual thermal transformations.
Barluenga
José
J
Instituto Universitario de Química Organometálica "Enrique Moles", Unidad Asociada al CSIC, Universidad de Oviedo, Julián Clavería 8, 33071 Oviedo, Spain.
Canteli
Rosa-María
RM
Flórez
Josefa
J