Nicotinic acid crown ethers: synthesis, complexation and reduction

2, 6-Bis (bromomethyl)nicotinic oxazoline 15, prepared from ethyl 2,6-dimethylnicotinate, was converted into the 1:1-macrocyclic oxazolines 19 and 22 as well as the isomeric macrocyclic dimers 20. Ethyl 2, 6-bis(bromomethyl)nicotinate 23, prepared from 6b, was converted to the corresponding 1:1-dibenzo-18-crown-6 macrocyclic analog 24. NMR and mass spectral data were used to ascertain the macrocyclic structures. Reaction of 22 with EtMgBr afforded, after oxidation, the 4-substituted pyridino macrocycle 26 in high yield. However, under identical conditions, the non-oxazoline macrocycle 27 was recovered in toto.