Synthesis and tautomeric structures of some novel thiophene-based bis-heterocyclic monoazo dyes

Efficient Syntheses of Some New Thiophene‐Based Heterocycles

“…Thus, the solvent-free reaction of (1) with benzaldehyde in the presence of sodium acetate at 155-160°C afforded the corresponding Schiff's base (18). Cyclization of the latter with thioglycolic acid in dry pyridine under reflux led to the formation of the corresponding thiazolidin-4-one derivative (19), on the basis of its spectral data. On the other hand, when a solution of 2-aminothiophene-3-carboxylate (1) in dry dioxane containing a catalytic amount of triethylamine was treated with chloroacetyl chloride at room temperature, the color of the reaction mixture quickly turned red.…”

“…The synthetic strategies adopted for the preparation of the desired compounds are illustrated in Schemes . The starting material, ethyl 2‐amino‐4‐methyl‐5‐(phenylcarbamoyl) thiophene‐3‐carboxylate ( 1 ) was easily accessible via the Gewald's reaction between acetoacetanilide, elemental sulfur, and ethyl cyanoacetate in the presence of morpholine according to the method prescribed in literatures (Scheme ).…”

“…All reactions were followed by TLC (silica gel, aluminum sheets 60 F254, Merck). Ethyl 2‐amino‐4‐methyl‐5‐(phenylcarbamoyl) thiophene‐3‐carboxylate ( 1 ) was prepared according to literatures procedures .…”

New disazo dyes derived from aminopyrazoles: synthesis, spectroscopic properties, computational study and structural properties

“…In our previous studies, the synthesis of certain azo dye molecules and their spectroscopic, tautomeric, electrochemical and optical properties was investigated 10,21,31‐33 . In the current study, we report the synthesis of and investigations concerning five new disazo compounds derived from 3‐amino‐5‐hydroxy‐1 H ‐pyrazole; and herein we also present some of their spectroscopic features and the results of corresponding ab initio computations in detail.…”

The Knoevenagel reactions of pregnenolone with cyanomethylene reagents: Synthesis of thiophene, thieno[2,3-b]pyridine, thieno[3,2-d]isoxazole derivatives of pregnenolone and their in vitro cytotoxicity towards tumor and normal cell lines

“…The analytical and spectral data were the basis of structure elucidation of 8a,b and 10a,b (Scheme 2). Thus, the 1 H NMR spectrum of compound 8a showed beside the expected signals, a singlet at Next, we studied the possibility of the reaction of compound 6 (E/Z) with elemental sulfur as a trial of Gewald's thiophene synthesis [26][27][28]. Thus, the reaction of compound 6 with elemental sulfur and a catalytic amount of triethylamine gave the thiophene 11 in an excellent yield.…”