INTRAMOLECULAR HYDROGEN-BONDING IN ACYLATED 2,2'-BIPYRIDINE-3,3'-DIAMINES

Various di- and monoacylated 2,2'-bipyridine-3,3'-diamines (amides 1a- f, 8, 9, ureas 1g-h, 8b and acylureas 1i-j) have been synthesized and characterized. All molecules show strong intramolecular hydrogen bondi ng between the acyl NH of one ring and the pyridine N-1 of the other ( and vice versa), as is deduced from the low field H-1 NMR resonances o f the acyl NH protons, which range from delta 12.6 to 15.0 ppm in CDCl 3. The nature of the secondary structure of the (di)acylated 2,2'-bipy ridine-3,3'-diamines has been investigated using a variety of techniqu es including variable-temperature H-1 NMR and CD spectroscopy.