Hemisynthesis, crystal structure and inhibitory effect of sesquiterpenic thiosemicarbazones and thiazolidin-4-ones on the corrosion behaviour of stainless steel in 1 M H₂SO₄ solution

Abstract

Treatment of thiosemicarbazones prepared from sesquiterpenes with ethyl 2‐bromoacetate in the presence of sodium acetate afforded the corresponding thiazolidin‐4‐ones. The structures of all the newly synthesized compounds were established by considering spectral and single‐crystal X‐ray diffraction data. The title compound, ethyl 2‐((Z)‐2‐{(Z)‐[(1aR,5aR,9aS)‐1,1‐dichloro‐1a,5,5,7‐tetramethyl‐1a,2,3,4,5,5a,8,9‐octahydro‐1H‐benzo[a]cyclopropa[b][7]annulen‐8‐ylidene]hydrazono}‐4‐oxothiazolidin‐3‐yl)acetate, C23H31Cl2N3O3S, 5, crystallizes in the orthorhombic noncentrosymmetric space group P212121 with Z = 4. Within the molecule in the crystal structure, the cyclohexene ring has an envelope conformation and the cycloheptane ring, to which it is fused, has a boat conformation. In the crystal, molecules are linked by C—H…Cl hydrogen bonds forming chains propagating along the b‐axis direction. The absolute configuration of the molecule in the crystal could be fully confirmed from anomalous dispersion effects [Flack parameter = −0.04 (2)]. Thiosemicarbazones 1 and 2 are efficient inhibitors for steel corrosion in 1 M H2SO4 solution, with a maximum efficiency of 92.28% at 10−3 M. Furthermore, thiosemicarbazone compounds were found to be more efficient than thiazolidin‐4‐one derivatives. In addition, cyclic voltammetry was used to characterize the tested molecules, as well to estimate the experimental value of the energy band gap.

Synthesis and Biological Evaluation of Novel Thiazole Analogs with Both Anti‐Proliferative and Mechanistic Analyses and Molecular Docking Studies

“…[37] Then, the oxygenated derivatives 3 a-b were obtained via oxidation reaction of compounds 2 a-b in the presence of N-bromosuccinimide (NBS) at room temperature in tetrahydrofuran (THF) as a solvent. [38] Next, the condensation reaction between the α, βunsaturated ketones 3 a-b with thiosemicarbazide derivatives catalyzed by concentrated sulfuric acid in refluxing ethanol leading to the corresponding thiosemicarbazones 4 a-c and 5 a--c in good yields. [38] Similarly, the enones 3 a-b were condensed with semicarbazide hydrochloride in the presence of sodium acetate in ethanol at reflux to furnish the semicarbazones 6 a-b.…”

“…[38] Next, the condensation reaction between the α, βunsaturated ketones 3 a-b with thiosemicarbazide derivatives catalyzed by concentrated sulfuric acid in refluxing ethanol leading to the corresponding thiosemicarbazones 4 a-c and 5 a--c in good yields. [38] Similarly, the enones 3 a-b were condensed with semicarbazide hydrochloride in the presence of sodium acetate in ethanol at reflux to furnish the semicarbazones 6 a-b. In the last step, the preparation of the target 1,3-thiazole derivatives was achieved via heterocyclization reaction.…”

Hybrid of the 1,2,3‐triazole nucleus and sesquiterpene skeleton as a potential antitumor agent: Hemisynthesis, molecular structure, Hirshfeld surface analysis, density functional theory, and in vitro cytotoxic and apoptotic effects

“…During the last two decades, several works in the literature propose various classical and catalytic methods for the preparation of 1,2,3-triazole [20,21]. As a first step, α,β-unsaturated ketone was prepared by treating cyclopropane sesquiterpene β-himachalene 2 [22,23] with the oxidizing agent SeO 2 in dichloromethane as a solvent. Subsequently, our study continued with the preparation of a 1,2,3-triazole by the treatment of α, β-unsaturated ketone 3 with azidomethyl benzene.…”

New enaminone sesquiterpenic: TiCl4-catalyzed synthesis, spectral characterization, crystal structure, Hirshfeld surface analysis, DFT studies and cytotoxic activity

“…Various modified synthetic pathways have been reported in literature for the synthesis of β-enaminones using Lewis acids, inorganic acids, ionic liquids, and transition metal catalysts [16]. In addition, other procedures of synthesis were used, such as, microwave [17] and ultrasound irradiations [18].However, α,β-unsaturated ketones react with alkyl-azides upon treatment with Lewis acids via 1,3-dipolar cycloaddition reactions leading to the formation products of expansion resulting from the intermolecular or intramolecular reaction (Azido-Schmidt) [19][20].On the other hand, the catalyst plays an important role in the preparation of 1, 2, 3-triazoline, this later facilitates the conversion to enamine or lactam analogues [21][22].The direct condensation of amines with 1,3-diketone by refluxing in the presence of various catalysts also gives two isomeric enaminones [23][24][25][26][27].According to this bibliographic overview and in continuation of our efforts in the valorization of sesquiterpenes by the synthesis of new compounds [28], we report a simple and selective method for the synthesis of an enaminone based on himachalene using 1,3-dipolar reaction of azide-alkyl with α,β-unsaturated ketone catalyzed by TiCl4.Both spectroscopic and theoretical studies had been undertaken using DFT/B3LYPmethod at 6-31+G(d,p) level. Also, the local reactivity indexes were carried out to investigate the plausible mechanisms for the regioselective synthesis of the compound 2.…”