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An organocatalytic Markovnikov-type bromo-aminoxidation of styrene derivatives was achieved by using in-situ-generated bromine and N-oxyl radicals, and the desired products were obtained in moderate to good yields. The bromine radical was generated from phenyliodine(III) bis(3-bromopropionate) through consecutive decarboxylation and deethylenation reactions via an organocatalytic SET process. Phenyliodine(III) bis(3-bromopropionate) also served as the oxidant for the generation of the N-oxyl radicals, while the N-oxyl radical was also crucial for the generation of the key β-enaminyl radical intermediate that was required for the SET process.

Synthesis of 2-styryl-quinazolines and 3-styryl-quinoxaline based sulfonates is reported via sp3 C–H functionalization in the presence of triethylamine (10 mol%). The resulting compounds were tested for α-glucosidase enzyme inhibition (in vitro) using acarbose as a standard drug (IC50 = 33 ± 2.65 μM) because α-glucosidases increase the carbohydrate digestion, and therefore the blood glucose levels. Inhibitors of this enzyme are known to reduce postprandial hyperglycemia. Among the compounds screened, 3o and 5n were found to be active with IC50 = 28 ± 1.99 μM and IC50 = 32 ± 2.11 μM, respectively, with a competitive mode of inhibition. The molecular docking analysis using the MAL12 homology model supported the in vitro results. The stability of 5g was studied using DFT calculation and it was found that the difference in total energy of the cis and trans (ΔE) isomers is −85.67 kcal mol−1. [ABSTRACT FROM AUTHOR]

A simple, metal-free protocol is reported for the one-pot synthesis of 2-styrylquinolines using a combination of 1,3-dimethyl urea (1,3-DMU) and L -tartaric acid (LTA) (in a 3 : 1 ratio) as a deep eutectic solvent (DES). The reaction proceeds via Friedländer annulation followed by Knoevenagel condensation (sp3 C–H activation) to give functionalized styrylquinoline derivatives in good to excellent yields. Density functional theory (DFT) calculations supported the experimental results on the role of DES in the enolization of the carbonyl compound (for Friedländer annulation) and the formation of enamine, key steps in sp3 C–H activation. Furthermore, the absorption and emission spectra of the resulting acyclic and cyclic compounds were recorded and it was found that compound 7c showed the highest emission band maximum (644 nm) due to intramolecular charge transfer. Also, compounds 7b and 8d exhibited a larger bathochromic shift at 551 nm and 558 nm, respectively, and compound 5n showed the highest Stokes shift (Δλ, at 182 nm). Compound 7e displayed noticeable colors in various solvents (solvatochromic effects). Some of the resulting compounds reported here can be used for developing fluorescent probes. [ABSTRACT FROM AUTHOR]

The methyl/methylene group present at the 5th position of 3,5‐dialkyl‐4‐nitroisoxazoles show characteristic reactivity because of the presence of −NO2 at the 4th position in the structure. This methyl/methylene is used for the generation of carbanion that undergo Knoevenagel condensation, vinylogous nitroaldol (Henry type), Mannich and Michael addition reactions. The unsaturated systems generated by Knoevenagel condensation are used for 1,4‐ and 1,6‐Michael addition, epoxidation, aziridination, cycloaddition ([2+1], [2+2], [2+3] and [4+2]) cascade/domino/tandem and dihydroxylation reactions. This resulted into the generation of many functionalized and complex organic molecules in asymmetric and racemic forms. Along with these, the isoxazole moiety has also been used as −COOH equivalent by basic/oxidative hydrolysis. This review describes recent literature on the synthetic applications of 3,5‐dialkyl‐4‐nitroisoxazoles and their derivatives for the generation of functionalized/complex heterocyclic compounds using above mentioned type of reactions and concepts. [ABSTRACT FROM AUTHOR]

The methyl/methylene group present at the 5th position of 3,5‐dialkyl‐4‐nitroisoxazoles show characteristic reactivity because of the presence of −NO2 at the 4th position in the structure. This methyl/methylene is used for the generation of carbanion that undergo Knoevenagel condensation, vinylogous nitroaldol (Henry type), Mannich and Michael addition reactions. The unsaturated systems generated by Knoevenagel condensation are used for 1,4‐ and 1,6‐Michael addition, epoxidation, aziridination, cycloaddition ([2+1], [2+2], [2+3] and [4+2]) cascade/domino/tandem and dihydroxylation reactions. This resulted into the generation of many functionalized and complex organic molecules in asymmetric and racemic forms. Along with these, the isoxazole moiety has also been used as −COOH equivalent by basic/oxidative hydrolysis. This review describes recent literature on the synthetic applications of 3,5‐dialkyl‐4‐nitroisoxazoles and their derivatives for the generation of functionalized/complex heterocyclic compounds using above mentioned type of reactions and concepts. [ABSTRACT FROM AUTHOR]

A green, efficient, and one‐pot method synthesis of functionalized 4H‐chromene‐isoxazole hybrids is reported via o‐hydroxy group directing cyclization of isoxazole‐styrenes and Michael addition of 3,5‐dimethyl‐4‐nitroisoxazole on 2‐imino‐2H‐chromene‐3‐carbonitrile (independent methods). The developed methodology was further extended for nitromethane, malononitrile, and alkylcyanoacetates as Michael donors. [ABSTRACT FROM AUTHOR]

Herein, the direct α‐sulfenylation of a series of β‐dicarbonyl, β‐ketophosphonate, and β‐ketonitrile compounds, mediated by sulfonium salts has been described. Traditionally, sulfonium salts which are synthesized by activation of dialkylsulfoxides serve as oxidizing agents or precursors of sulfur ylide. In this transformation, sulfonium salts as readily prepared and operationally simple sulfenylation reagents firstly achieved alkylsulfenylation of various activated C(sp3)−H bonds with the formation of tetra‐substituted carbon center. [ABSTRACT FROM AUTHOR]

Catalyst‐free synthesis of the isoxazole‐spirooxindole‐tetrahydrothiophene hybrids is reported. Formation of 1,4‐thia‐Michael and intramolecular aldol reactions were observed (instead of 1,6‐thia‐Michael followed by vinylogous Henry reactions) in a regioselective fashion to give new isoxazole‐spirooxindole‐tetrahydrothiophene hybrids with excellent yields. [ABSTRACT FROM AUTHOR]