Synthesis of thienopyrimidine-pyrazolo[3,4-b]pyridine hybrids was written by Park, Jae Woo;Song, Yang-Heon. And the article was included in Heterocyclic Communications in 2017.Electric Literature of C8H8N2S This article mentions the following:
New hybrid compounds, thienopyrimidinyl-1H-pyrazolo[3,4-b]pyridines I [R1 = R2 = H; R1R2 = (CH2)3, (CH2)4; R3 = 4-Me, 4-MeO, 4-Br] and II were efficiently synthesized by the three-component reaction of 3-phenyl-1-(thienopyrimidin-4-yl)-1H-pyrazol-5-amines, benzoylacetonitrile and an aromatic aldehydes in the presence of FeCl3 on basic alumina. In the experiment, the researchers used many compounds, for example, 2-Amino-5,6-dihydro-4H-cyclopenta[b]thiophene-3-carbonitrile (cas: 70291-62-2Electric Literature of C8H8N2S).
2-Amino-5,6-dihydro-4H-cyclopenta[b]thiophene-3-carbonitrile (cas: 70291-62-2) belongs to nitriles. Nitrile carbon shifts are in the range of 115–125 ppm whereas in isonitriles the shifts are around 155–165 ppm. In addition, Nitriles can react with alkynes, which leads to an increase in carbon chain length (carbocyanation).Electric Literature of C8H8N2S
Referemce:
Nitrile – Wikipedia,
Nitriles – Chemistry LibreTexts