Liang, Chengyuan et al. published their research in Journal of Sulfur Chemistry in 2013 | CAS: 70291-62-2

2-Amino-5,6-dihydro-4H-cyclopenta[b]thiophene-3-carbonitrile (cas: 70291-62-2) belongs to nitriles. Nitriles are polar, as indicated by high dipole moments. As liquids, they have high relative permittivities, often in the 30s. In addition, Nitriles can react with alkynes, which leads to an increase in carbon chain length (carbocyanation).Name: 2-Amino-5,6-dihydro-4H-cyclopenta[b]thiophene-3-carbonitrile

First Gewald reaction ignited by sodium polysulfide: greener ultrasound-promoted synthesis of substituted 2-aminothiophenes in the absence of catalyst was written by Liang, Chengyuan;Lei, Dong;Wang, Xiuzhen;Zhang, Qingqing;Yao, Qizheng. And the article was included in Journal of Sulfur Chemistry in 2013.Name: 2-Amino-5,6-dihydro-4H-cyclopenta[b]thiophene-3-carbonitrile This article mentions the following:

In this paper, a modified and facile Gewald reaction triggered by sodium polysulfide in the absence of catalytic base was developed. This approach involves a one-pot ultrasound-irritated aqueous reaction between ketones or aldehydes, malononitrile and sodium sulfide [Na2(Sx)] [sodium polysulfide, sodium sulfide [Na2(S4)], sodium sulfide [Na2(S6)], sodium sulfide (NaS)]. which are converted into the corresponding 2-aminothiophene derivatives in moderate to high yields. In comparison with conventional methods, the prominent features of this ultrasound-mediated procedure are exptl. simplicity, good functional group tolerance, atom efficiency, and the use of water as a green solvent. The title compounds thus formed included and amine nitrile [2-amino-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carbonitrile] (I) and an analog, 2-amino-5,6-dihydro-4H-cyclopenta[b]thiophene-3-carbonitrile (II), 2-amino-4-ethyl-3-thiophenecarbonitrile, 2-amino-4-(phenylmethyl)-3-thiophenecarbonitrile. The synthesis of the target compounds was achieved using cyclohexanone, cyclopentanone, butanal, propanal, hexanal, benzeneacetaldehyde, benzenepropanal as starting materials. In the experiment, the researchers used many compounds, for example, 2-Amino-5,6-dihydro-4H-cyclopenta[b]thiophene-3-carbonitrile (cas: 70291-62-2Name: 2-Amino-5,6-dihydro-4H-cyclopenta[b]thiophene-3-carbonitrile).

2-Amino-5,6-dihydro-4H-cyclopenta[b]thiophene-3-carbonitrile (cas: 70291-62-2) belongs to nitriles. Nitriles are polar, as indicated by high dipole moments. As liquids, they have high relative permittivities, often in the 30s. In addition, Nitriles can react with alkynes, which leads to an increase in carbon chain length (carbocyanation).Name: 2-Amino-5,6-dihydro-4H-cyclopenta[b]thiophene-3-carbonitrile

Referemce:
Nitrile – Wikipedia,
Nitriles – Chemistry LibreTexts