Gold-catalyzed addition reaction between creatinine and isatin: A sustainable and green chemistry approach for the diastereoselective synthesis of 3-substituted-3-hydroxyisatins

Step-Economical Mechanosynthesis of Hybrid Azoles: Deciphering Their π-Orbital and Pharmacological Characteristics

A hybrid pharmacophore strategy for unifying 1,2,3-triazole with 1,2,4-triazole cores to prepare mixed triazoles was accomplished by a ball-milling approach. The developed chemistry works under the catalysis of cupric oxide nanoparticles with salient features like one-jar operation, lower number of synthetic steps, catalyst recyclability, time-dependent product control, and good overall yields. π-Orbital properties based on theoretical calculations supported the suitability of these molecules for pharmacological screening. Therefore, the biological potency of the synthesized molecules was evaluated for antioxidant, anti-inflammatory, and anti-diabetic activities. By virtue of their proton-donating tendency, all compounds showed promising radical-scavenging activity with the inhibition level reaching up to 90 %. These molecular hybrids also exhibited anti-inflammatory and anti-diabetic potencies similar to those of standard compounds, owing to their electron-rich nature. Finally, α-amylase inhibitory potential was demonstrated in silico; significant regions necessary for enzyme inhibition were identified by hydrogen bonding interactions.

Mechanosynthesis of Triazolyl-bis(indolyl)methane Pharmacophores via Gold Catalysis: A Prelude to Their Molecular Electronic Properties and Biological Potency

Chemical structures possessing both 1,2,3-triazole and bis(indolyl)methane fragments gained considerable interest in drug synthesis owing to their established biological efficacies. However, 1,2,3-triazoles linked at the bridging position of bis(indolyl)methane is a logical and unexplored design approach. In this regard, nine new triazolyl-bis(indolyl)methane conjugates under AuCl catalyzed ball-milling conditions were accomplished. Comparative evaluation on absorptive and emissive properties of the synthesized dyads were also analyzed. To unravel the influence of different peripheral substituents on the electronic structure and π-orbital properties, theoretical investigations were performed. Screening of molecules for free radical scavenging, anti-inflammatory and antidiabetic showed comparable potency against reference drugs. In particular, compounds 7 h, 7 d and 7 a displayed good efficiency of α-amylase inhibition. The DNA gyrase inhibitory potential of all compounds were assessed in silico which revealed high binding affinity (ΔG=-8.99 Kcal/mol) for 7 i followed by 7 h (ΔG=-7.80 Kcal/mol) with the targeted protein.

Gold-catalyzed multicomponent reactions

Multicomponent reactions (MCRs) have emerged as an important branch in organic synthesis for the creation of complex molecular structures. This review is focused on gold-catalyzed MCRs with a special emphasis on the recent developments.

Cycloisomerization of π-Coupled Heteroatom Nucleophiles by Gold Catalysis: En Route to Regiochemically Defined Heterocycles

Since the dawn of millennium, catalytic gold chemistry is at the forefront to set off diverse organic reactions via unique activation of π-bonded molecules. Within this purview, cycloisomerization of heteroatom nucleophiles linked to a π-system is one of the well recognized chemistry for the construction of numerous heterocyclic cores. Though the rudimentary aspects of this transformation are reviewed by several groups in different timeline, a holistic view on regiochemistry of such reactions went largely overlooked. Hence, this account emphasizes the gold catalyzed regioselective cycloisomerization of structurally distinctive π-connected hetero-nucleophiles leading to different heterocycles documented in the last two decades. From an application perspective, this account also highlights those methodologies which find a role in the total synthesis of natural products. Wherever appropriate, mechanistic details and contributing factors for selectivity are also discussed.

Engaging Isatins in Multicomponent Reactions (MCRs) - Easy Access to Structural Diversity

Multicomponent reactions (MCRs) are a valuable tool in diversity-oriented synthesis. Its application to privileged structures is gaining relevance in the fields of organic and medicinal chemistry. Isatin, due to its unique reactivity, can undergo different MCRs, affording multiple interesting scaffolds, namely oxindole-derivatives (including spirooxindoles, bis-oxindoles and 3,3-disubstituted oxindoles) and even, under certain conditions, ring-opening reactions occur that leads to other heterocyclic compounds. Over the past few years, new methodologies have been described for the application of this important and easily available starting material in MCRs. In this review, we explore these novelties, displaying them according to the structure of the final products obtained.

Harnessing the TEMPO-Catalyzed Aerobic Oxidation for Machetti-De Sarlo Reaction toward Sustainable Synthesis of Isoxazole Libraries

A practical synthesis of isoxazole/isoxazoline derivatives via Machetti-De Sarlo reaction under sustainable conditions has been accomplished. This protocol involves the use of readily available 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) to catalyze the cyclocondensation of primary nitroalkanes with alkynes/alkenes to afford a library of isoxazole/isoxazoline products. From an eco-benign perspective, notable advantages of this method are as follows: (i) water as the solvent, (ii) air as the oxidant, (iii) transition metal-free, (iv) no base required, (v) no toxic byproduct, (vi) no need of solvent extraction, (vii) diverse substrate scope, (viii) high chemical yields, (ix) excellent chemo- and regioselectivity, (x) short reaction time, (xi) gram-scale synthesis, (xii) extension to heterogeneous version, and (xiii) catalyst recyclability. For these reasons, the developed method is appropriate for safe laboratory use and can be expected to inspire the progress of TEMPO-based organocatalysis for the preparation of isoxazole/isoxazoline moieties in an environmentally benign fashion.

Fine-tuning the optoelectronic chattels of fluoreno-thiophene centred molecular semiconductors through symmetric and asymmetric push–pull switch

Optoelectronic properties of symmetrical and unsymmetrical fluoreno-thienyl π-semiconductors were studied.

New D–π-A push–pull chromophores as low band gap molecular semiconductors for organic small molecule solar cell applications

Low band gap molecular semiconductors based on push–pull systems with appropriate HOMO–LUMO energy levels for organic photovoltaic applications were accomplished.