α,5-Didehydro-3-picoline Diradicals from Skipped Azaenediynes: Computational and Trapping Studies of an Aza-Myers−Saito Cyclization
journal contributionposted on 10.06.2004, 00:00 by Liping Feng, Dalip Kumar, David M. Birney, Sean M. Kerwin
On the basis of density functional calculations, the isomerization of skipped azaenediynes (C-alkynyl-N-propargylimines) to azaenyne allenes and subsequent rapid aza-Myers−Saito cyclization to α,5-didehydro-3-picoline were predicted. We prepared the N-propargylimine of 1-phenyl-3-tri(isopropyl)silylprop-2-yn-1-one, which undergoes proto-desilylation and isomerization to an azaenyne allene when treated with tetrabutylammonium fluoride. In the presence of 1,4-cyclohexadiene, this azaenyne allene affords 6-phenyl-3-picoline and other products corresponding to the trapping of an α,5-didehydro-3-picoline diradical.