An efficient, one-pot, regioselective synthesis of 2-aryl/hetaryl-4-methyl-5-acylthiazoles under solvent-free conditions

Design, synthesis and characterization of tetra substituted 2,3-dihydrothiazole derivatives as DNA and BSA targeting agents: advantages of the visible-light-induced multicomponent approach

This report describes the visible-light-induced one-pot multicomponent regioselective synthesis of a series of 5-aroyl-3-((arylidene)amino)-2-((arylidene)hydrazono)-4-methyl-2,3-dihydrothiazoles as DNA and BSA targeting agents. The multicomponent condensation of thiocarbohydrazide and aldehydes with α-bromo-1,3-diketones, generated in situ by the bromination of unsymmetrical 1,3-diketones with NBS using white LED light as an environmental friendly source in the presence of EtOAc solvent furnished the titled 2,3-dihydrothiazole derivatives in excellent yields. The exact regioisomeric structure was identified unambiguously by employing multinuclear 2D-NMR spectroscopy [1H-13C] HMBC; [1H-13C] HMQC and [1H-15N] HMBC. Furthermore, the binding characteristics of the synthesized 2,3-dihydrothiazole derivatives were assessed with double-stranded calf-thymus DNA duplex (ct-DNA) and bovine serum albumin (BSA). Initial screening of all the synthesized 2,3-dihydrothiazole derivatives using various in silico techniques including molecular reactivity analysis, Lipinski rule and molecular docking, concluded 5-(4'-chlorobenzoyl)-3-((4''-methoxybenzylidene)amino)-2-(4'''-methoxybenzylidene)hydrazono)-4-methyl-2,3-dihydrothiazole derivative 6a as the most suitable compound for studying binding interaction with DNA and BSA. Additionally, to illustrate the ex vivo binding mode of 6a with DNA and BSA, several spectroscopic techniques viz. UV-visible, circular dichroism (CD), steady-state fluorescence and competitive displacement assays were carried out.

Enhancing C-S and C-N bond formation with ultrasound assistance: lipase-catalyzed synthesis of 2,4-disubstituted thiazole derivatives from arylethanones and thioamides

The present study explores an innovative approach for the efficient synthesis of 2,4-disubstituted thiazole derivatives, a class of compounds with diverse biological and pharmaceutical significance. This research presents lipase as a highly effective and environmentally friendly catalyst for thiazole synthesis. Under mild circumstances, the condensation of aryl ethenone, KBrO3, and thioamide is aided by using ultrasonic energy. Moreover, we harness the power of ultrasound irradiation to accelerate the reaction, reducing reaction times and improving product yields. The lipase-catalyzed, ultrasound-assisted synthesis presented in this study represents a greener and more sustainable alternative to traditional synthetic pathways for these important compounds, offering promising potential for applications in medicinal chemistry and drug development. This approach holds the promise of advancing the field of thiazole synthesis, contributing to more sustainable and efficient chemical processes.

Visible-light-induced C-S bond formation in the synthesis of 2,4-disubstituted thiazoles through cascade difunctionalization of acetophenone: a greener approach

A groundbreaking approach has been developed for synthesizing 2,4-disubstituted thiazoles using an eco-friendly and metal-free approach. This novel method utilizes methyl aryl ketones, N-bromo-succinimide (NBS), and thioamides in water as a green reaction medium under visible light irradiation. Using NBS as a bromine source, the reaction takes place through an in situ α-bromination method. This approach does not require any catalyst, which makes it exceptionally beneficial for the environment. The advantages of this efficient approach are manifold and include the use of greener conditions, absence of metals, easy isolation of products, cost-effectiveness, non-toxicity, and reliance on renewable energy sources like visible light. Moreover, this technique offers higher product purity and excellent yield, enhancing itsappeal.

Serendipitous N,S-difunctionalization of triazoles with trifluoromethyl-β-diketones: access to regioisomeric 1-trifluoroacetyl-3-aryl-5-(2-oxo-2-arylethylthio)-1,2,4-triazoles as DNA-groove binders

In the present research work, a serendipitous regioselective synthesis of DNA targeting agents, 1-trifluoroacetyl-3-aryl-5-(2-oxo-2-arylethylthio)-1,2,4-triazoles, has been achieved through the one-pot cascade reaction of 3-mercapto[1,2,4]triazoles with trifluoromethyl-β-diktetones in presence of NBS instead of the cyclized thiazolo[3,2-b][1,2,4]triazole. The present protocol offered a unique approach for functionalizing both N-acylation and S-alkylation in a concerted fashion. The structures of the regioisomeric products were thoroughly characterized by heteronuclear 2D NMR experiments. Facile scalability and excellent atom economy through easily available starting reactants are the notable features of the present sustainable protocol. Targeting tumor cell DNA with minor groove-binding small molecules has proven highly effective in the recent past, drawing significant attention for combating tumor-related afflictions. In this context, the synthesized analogs were primarily screened for their ability to bind with the DNA duplex d(CGCGAATTCGCG)2 using molecular modeling tools. Additionally, the most promising compound 14m was deployed as a probe for DNA sensing and interaction mechanisms with calf thymus (ct)DNA through various spectral techniques at a physiologic temperature of 37 °C. It has been found that the compound demonstrated a strong binding affinity (Kb = 1 × 105 M-1) with double-helical DNA, particularly within the minor groove, resulting in the formation of a stable complex through static quenching (Kq = 5.86 ± 0.11 × 1012 M-1 s-1). The fluorescent displacement assay confirmed that the quencher binds to the minor groove of ctDNA, further supported by circular dichroism and viscosity studies.

Visible Light-Prompted Regioselective Synthesis of Novel 5-Aroyl/hetaroyl-2',4-dimethyl-2,4'-bithiazoles as DNA- and BSA-Targeting Agents

Organic transformations mediated by visible light have gained popularity in recent years as they are green, renewable, inexpensive, and clean and yield excellent products. The present study describes cyclo-condensation of 2-methylthiazole-4-carbothioamide with differently substituted α-bromo-1,3-diketones achieved by utilizing a white light-emitting diode (LED) (9W) to accomplish the regioselective synthesis of novel 5-aroyl/hetaroyl-2',4-dimethyl-2,4'-bithiazole derivatives as DNA/bovine serum albumin (BSA)-targeting agents. The structure characterization of the exact regioisomer was achieved unequivocally by heteronuclear two-dimensional nuclear magnetic resonance (2D-NMR) spectroscopy [1H-13C] HMBC; [1H-13C] HMQC; and [1H-15N] HMBC. In silico toxicity studies indicated that the synthesized compounds exhibit low toxicity risks and adhere to the rules of oral bioavailability without any exception. Computational molecular modeling of the bithiazole derivatives with the dodecamer sequence of the DNA duplex and BSA identified 5-(4-chlorobenzoyl)-2',4-dimethyl-2,4'-bithiazole 7g as the most suitable derivative that can interact effectively with these biomolecules. Furthermore, theoretical results concurred with the ex vivo binding mode of the 7g with calf thymus DNA (ct-DNA) and BSA through a variety of spectroscopic techniques, viz., ultraviolet-visible (UV-visible), circular dichroism (CD), steady-state fluorescence, and competitive displacement assay, along with viscosity measurements.

An expeditious on-water regioselective synthesis of novel arylidene-hydrazinyl-thiazoles as DNA targeting agents

A series of twenty novel (E)-arylidene-hydrazinyl-thiazole derivatives has been synthesized employing α-bromo-β-diketones, thiosemicarbazide, and aromatic/heteroaromatic aldehydes with a simple and facile one-pot multicomponent reaction passageway. This organic transformation proceeds efficiently in aqueous media and demonstrated a large functional group tolerance. The structures and stereochemistry of the regioisomeric product were rigorously characterized using heteronuclear 2D NMR experiments. The binding potential of the synthesized analogs with B-DNA dodecamer d(CGCGAATTCGCG)₂ was primarily screened using molecular modeling tools and further, mechanistic investigations (either groove or intercalation) were performed using various spectroscopic techniques such as UV-Visible, Fluorescence, and Circular dichroism. The absorption spectra showed a hyperchromic shift in the absorption maxima of ctDNA with successive addition of thiazole derivatives, implying groove binding mode of interactions, further supported by displacement assay and circular dichroism analysis. Furthermore, steady-state fluorescence analysis revealed the static mode of quenching and moderate bindings between the ligand and DNA biomolecule. The competitive studies showed that the derivatives having a pyridinyl (heteroaromatic) group in their structure, bind with the nucleic acid of calf-thymus (ctDNA) more effectively in the minor groove region as compared with the aromatic substitutions.