A practical process for the synthesis of translocator protein 18kDa imidazopyridine ligand

In this article, an effective feasible method to synthesize translocator protein 18kDa (TSPO) imidazopyridine ligand 7 is discussed. A new procedure for the synthesis of the key intermediate 17 has been developed in four steps (condensation, diazo reaction, hydrolysis, amidation) from 2-aminopyridine 18. The overall yield was increased from 18% to 31.6%. One of the key steps is using activated copper powder as a catalyst in several cycles. Finally, reduction of 17 with Zn dust completed the synthesis of TSPO imidazopyridine ligand 7 in 86% yield.