Synthesis and characterization of some novel polyfunctionally substituted indeno[2,1-b]thiophene compounds derived from indanones

Activation of Elemental Sulfur by Electrogenerated Cyanomethyl Anion: Synthesis of Substituted 2‐Aminothiophenes by the Gewald Reaction

“…The curve relative to S 8 shows two reduction peaks, the first at a potential of À0.75 V and the second at a potential of À1.15 V. After the addition of cyanomethyl anion, the two peaks desappeared.…”

“…[4] They also show antimicrobial activity against various Gram(+) and Gram(À) bacteria and fungi, [5] antibacterial activity against S. aureus, B. subtilis and E. coli, [6] as well as antioxidant and anti-inflammatory activity. [7] Moreover, these molecules are dyes [8] and precursors of azo dispersed dyes. [9] Many are the routes to this kind of product (such as, for example, the cyclization of thioamides and their S-alkylates), [1] but usually they involve difficult preparation of the starting materials, multistep synthesis and do not produce high yields.…”

The Gewald reaction in dye chemistry

“…1‐Indanone undergoes the Gewald reaction via the two‐step process (version 3) with malononitrile, giving a Knoevenagel condensation product, which cyclises with sulfur and diethylamine to yield the corresponding indeno[2,1‐ b ]thiophene, followed by acetylation with acetic anhydride. Finally, condensation of acetylated indeno[2,1‐ b ]thiophene with various p ‐substituted arylaldehydes in the presence of piperidine and ethanol afforded, by the elimination of the acetyl group, yellow‐orange to orange‐red styryl dyes 47 (Scheme ) . It was observed that the introduction of an electron‐withdrawing nitro group in the p ‐position of the phenyl ring caused a significant bathochromic shift, whereas the introduction of an electron‐donating N , N ‐dimethylamino group in the p ‐position of the phenyl ring caused a large hypsochromic shift in accordance with the theory.…”

“…The scope and synthetic utility of the Gewald reaction have been demonstrated by various examples listed in Tables 1-3. The reaction has applications in several applied fields, such as pharmaceuticals/biomedicine [24,28,29,31, 32,34,35,39,40,42,44,51-53,71,73,74,77,78,80,83-85,88,91-94,96,98-106,113-116,118-123,125-127,129-132,135-138, 141,144,147,149,151,158,161-164,166,179,180,239], agrochemicals [91,101,103,106,108,114,122,292], carbohydrate conjugates [293,294], sugar cane ripeners [295][296][297], peptide analogues [229,230], dyestuffs [61,62,67,86,87,128,152,[155][156][157]175,[282][283][284][285]287,288,290,291,[300][301][302][303], and electronic materials [186,237,238,265,298,…”

“…In contrast to intensive studies on azo dyes based on 2aminothiophene derivatives, considerable interest is shown in the use of the electron-withdrawing ability of 1-indanone as a precursor for the preparation of polyfunctionally substituted indeno [ [175]. It was observed that the introduction of an electron-withdrawing nitro group in the p-position of the phenyl ring caused a significant bathochromic shift, whereas the introduction of an electron-donating N,N-dimethylamino group in the pposition of the phenyl ring caused a large hypsochromic shift in accordance with the theory.…”