5-Aminocyclopentadienes by intramolecular addition of enolether to aminoallene functionalities

3-(1-Alkoxyvinyl)-1-aminoallenes were generated by conjugate addition of acyclic and cyclic (1-alkoxyvinyl)cuprates with the semicyclic propyne iminium salt . They isomerized smoothly into spiroannellated cyclopentadienes through a 1,5-cyclization that in some cases occurred already at ≤20°C. (1-Methoxyallenyl)cuprates reacted with salt in a 2:1 ratio to give the 5,5-dimethoxy-4-methylenepentalene-1-spiro-2′-dihydroindole derivative . The thermal isomerization of morpholinoallene into cyclopentadiene indicates that the novel 1,5-cyclization can be extended to other 3-(1-alkoxyvinyl)-1-aminoallenes as well.