Thermal Cyclodimerization of Aliphatic Secondary C,N-Dilithioallylamine Derivatives

Article abstract of DOI:10.1021/jo960048o

β-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 β-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.