Novel dibenzo-monoaza-12-crown-3, -15-crown-4, -18-crown-5 and -21-cro
wn-6 derivatives (7a-d) were synthesized Two independent methods were
developed for the heterocyclization and the better one was optimized T
he structure of crowns 7a,b,c was confirmed by single-crystal X-ray di
ffraction. Copyright (C) 1996 Elsevier Science Ltd