Two-step synthesis of indeno[1,2-b]furazanopyrazines through combination of the SNH and Heck reactions

Enamines generated in situ from aliphatic amines and acetone react with 5-(2-bromophenyl)furazano[3,4-b]pyrazines via the nucleophilic substitution of hydrogen atom of the pyrazine ring. A representative of 9H-indeno[1,2-b]furazanopyrazin-9-ylidene ring system has been accessed by exploiting the intramolecular Heck cyclization of the obtained S_N^H-product. Several compounds derived from the S_N^H reaction, namely, N-alkyl-1-[6-(2-bromophenyl)furazano[ 3,4-b]pyrazin-5-yl]prop-1-en-2-amines, proved to exhibit a bacteriostatic activity in vitro against Mycobacterium tuberculosis H₃₇Rv