An Improved Synthesis of 2,3-Diamino-5,6-dichloropyrazine: A Useful Heterocyclic Scaffold

Abstract 2,3-Diamino-5,6-dichloropyrazine represents a valuable but underexplored heterocyclic building block. Due to the use of harsh conditions and lack of selectivity surrounding the known literature synthesis, we developed a more accessible and selective three-step route from 2-aminopyrazine. Challenging conditions are avoided by using a high-yielding dichlorination with N-chlorosuccinimide (NCS), which is followed by a regioselective amination. The installation of the last chlorine atom using 1-chloro-1,2-benziodoxol-3(1H)-one is rapid, enabling access to 2,3-diamino-5,6-dichloropyrazine in an improved overall yield (41%).