HIGH-YIELD PREPARATION OF 4'-(4-BROMOPHENYL)-2,2'6',2''-TERPYRIDINE BY A CONDENSATION REACTION - DETERMINATION OF THE STEREOCHEMISTRY OF 2 COMPLEX BY-PRODUCTS BY A COMBINATION OF MOLECULAR MECHANICS AND NMR-SPECTROSCOPY

An improved high yield synthesis of 4'-(4-bromophenyl)-2,2': 6',2 ''-t erpyridine from 2-acetylpyridine (1) and 4-bromobenzaldehyde (2) has b een developed, using a two-step aldol condensation. In this, the inter mediate azachalcone 3 was isolated, then reacted with N-[2-oxo-2-(2-py ridyl)ethyl]pyridinium iodide, prepared from 1, using ammonium acetate both as a base and as a ring closure agent. It could also be shown th at one step aldol condensation of 1 and 2 gave low yields of the desir ed terpyridine due to facile formation of polycondensation products, T wo of these, 8 and 10, could be isolated in moderate yields from conde nsation reactions. The structure and relative configuration of these c ompounds were determined by a comparison of observed experimental NMR parameters with theoretical values. calculated by molecular mechanics.