Amino‐substituted 2‐Azaallenium Salts

Abstract

Abstract Nitrilium salts ( 14a – i ) react with imines ( 15a – e ) to afford the mono‐ to tetraaza‐substituted 2‐azaallenium salts 16a – w in high yields. The stereochemistry of these compounds is discussed in terms of an allenic geometry ( A ) and a planar 1,3‐diaza‐1,3‐butadienium structure ( B ), respectively. According to the IR, 1 H and 13 C NMR spectra, the azaallenium salts 16 are rather flexible around the central nitrogen atom. In solution at least 16a – d assume chiral conformations similar to those of allenes. By DNMR measurements barriers to hindered rotation around the CN + C axis were found to range from δ G 173 † = 36 ± 1 kJmol –1 for 16a to more than 90 kJmol –1 for 16c . According to an X‐ray structural analysis, 16o crystallizes in an almost perfect allene geometry ( A ). – Some interesting 13 C‐ 14 N couplings of the nitrilium salts 14 are reported.