Non-template syntheses and monoalkylation of an aza macrocycle containing 2,2′-bipyridine

Abstract

Cross-condensation of 6,6′-diamino-2,2′-bipyridine (3) with 6,6′-dibromo-2,2′-bipyridine (2) gave an azamacrocycle containing two aza-bridged 2,2′-bipyridine moieties, 3H,10H-tetrapyrido[2,1,6-de:2′,1′,6′-gh:2″,1″,6″-kl:2‴,1‴,6‴-na][1,3,5,8,10,12]hexa-azacyclotetradecine (1), in high yield without metal template. Furthermore, compound (1) could be obtained in >90% yield directly from 6,6′-dibromo-2,2′-bipyridine (2) by heating the latter with ammonia in an autoclave without metal template. N-Alkylation of compound (1) with n-hexyl bromide in the presence of tetra-n-butylammonium bromide gave exclusively the mono-N-n-hexyl derivative of (1), 10-hexyl-3H,10H-tetrapyrido[2,1,6-de:2′,1′,6′-gh:2″,1″,6″-kl:2‴,1‴,6‴-na][1,3,5,8,10,12]hexa-azacyclotetradecine (4). Evidence for the tautomerism of the mono-n-hexyl derivative (4) was provided by the ¹H n.m.r. and absorption spectra.