Syntheses and structural properties of 1,8-diazacyclotetradeca-3,5,10,12-tetraynes

The syntheses of 1,8-diazacyclotetradeca-3,5,10,12-tetrayne (2a), its N,N'- dimethyl (2b), N,N'-diethyl (2c), N,N'-diisopropyl (2d), N,N'-diallyl (2e), and N,N'-dibenzyl (2f) derivatives were achieved in a one-pot procedure fr om primary amines and 1,6-dibromo-2,3-hexadiyne (4). Diffraction studies on single crystals of 2c-2f reveal a chair conformation with the substituents in the diaxial positions. The preference of the axial orientation of the s ubstituents on the nitrogens in 2c-2f is due to several contributions: mini mal synaxial 1,3 interactions of the NR bond and the lone pair with adjacen t CH and CC bonds.