2-aza-1,3-dienes - Methods of Synthesis and Stereochemical Studies

2-Aza-1,3-dienes bearing an activating trialkylsilyloxy group at C-3 have been prepared via three routes. The first route involves the silylation of N-acylimidates which are readily available from iminoether hydrochlorides and acid chlorides. According to a more general route towards these doubly activated dienes, N-trialkylsilylimidates and N-trialkylsilylimines derived from non-enolizable aldehydes were conveniently converted in a one-pot sequence into the corresponding azadienes by reaction with an acid chloride in the presence of triethylamine. Finally, cyclic dienes could be prepared by direct silylation of glutarimide on both oxygens with trialkylsilyltriflate in the presence of triethylamine. The configuration and conformation of 2-azadienes have been established by H-1, C-13 and N-15 NMR spectroscopy.