New 2,5‐dihydroimidazole‐1‐oxyls with functional side groups (N, O, S donors)

A series of functionalized 2,5‐dihydro‐1‐hydroxy‐2‐R 1 ‐2‐R 2 ‐4‐R 3 ‐imidazoles were prepared by cyclocondensation of α‐oxo hydroxylamines with ketones R 1 R 2 C = O in the presence of ammonia (R 1 = R 2 = 2‐pyridyl, 4,5‐diazafluoren‐9‐ylene, R 3 = Me; R 1 = CH 2 OCOMe, CH 2 OCOPh, 2‐thienyl, CH 2 OH, CO 2 K, R 2 = R 3 = Me; R 1 = Py, R 2 = Me, R 3 = Ph; R 1 = R 2 = CH 2 OCOPh, CH 2 OH, R 3 = Me) and oxidized to the corresponding nitroxide radicals. The structures of 2′,5′‐dihydro‐1′‐hydroxy‐4′,5′,5′‐trimethylspiro[4,5‐diazafluoren‐9,2′‐imidazole] (2) and of 2‐(acetoxymethyl)‐2,5‐dihydro‐2,4,5,5‐tetramethylimidazole‐1‐oxyl (14) were determined by X‐ray diffraction. In the crystal 2 forms one‐dimensional chains through hydrogen bonding between N atoms of the hydroxylamine and imidazoline groups.