Synthesis of derivatives of aza[14]annulene, aza[16]annulene, aza[18]annulene, aza[20]annulene, and aza[22]annulene, diatropic and paratropic vinylogues of pyridine

Abstract

Following the reaction sequence shown in the scheme, the title compounds (II), (VI), (VIII) (stable), (X), (XII) (relatively stable), (XIV) and (XVI) (unstable) are available.

4:7,10:13-Diepoxy-1-aza[16]annulene and 3:6,9:12,15:18-triepoxy-2-chloro-1-aza-[18]annulene as the first examples of oxygen-bridged aza-[4n]- and -[4n+ 2]annulenes

“…data of (5) confirmed this; of the ten annulene protons, nine resonated at 6 4.50-5.85, and the NH proton, which is located inside the ring, resonated at extremely low field (6 15.9). This showed that (5) is clearly paratropic and that the observed high field resonances are comparable with those of (6) [6 3.514.951 and (7) [6 4.0CL5.001. This proves convincingly that the keto form (5a) possesses a 17-membered skeleton was confirmed by the presence of a paramagnetic ring current, exhibiting resonances for all the outer annulene protons at 6 4.70-5.57 (8H), except for two protons, which resonated at 6 7.01.…”