Synthesis of Bi-, Ter-, and Quaterpyridinecarboxylates via Propargylisoxazole-Pyridine Rearrangement.

A flexible method was developed for the synthesis of 2,2'-bi-, 2,2':6',2″-ter-, and 2,2':6',2'':6'',2‴-quaterpyridines containing a nicotinic acid moiety. The approach involves the Fe(II)/Au(I)-catalyzed rearrangement of key 4-propargylisoxazole building blocks bearing a pyrid-2-yl or quinolin-2-yl substituent at the 3-position and Pd(0)-catalyzed cross-coupling reactions.