A highly efficient [3+2] cycloaddition of nitrile oxides and azomethine imines to N-vinylpyrroles

Ultrasound-assisted one-pot green synthesis of new N- substituted-5-arylidene-thiazolidine-2,4-dione-isoxazoline derivatives using NaCl/Oxone/Na3PO4 in aqueous media

A rapid and green method for the synthesis of novel N-thiazolidine-2,4-dione isoxazoline derivatives 5 from N-allyl-5-arylidenethiazolidine-2,4-diones 3 as dipolarophiles with arylnitrile oxides via 1,3-dipolar cycloaddition reaction. The corresponding N-allyl substituted dipolarophiles were prepared by one-pot method from thiazolidine-2,4-dione with aldehydes using Knoevenagel condensation followed by N-allylation of thiazolidine-2,4-dione in NaOH aqueous solution under sonication. In addition, the isoxazoline derivatives 5 were synthesized by regioselective and chemoselective 1,3-dipolar cycloaddition using inexpensive and mild NaCl/Oxone/Na₃PO₄ as a Cl source, oxidant and/or catalyst under ultrasonic irradiation in EtOH/H₂O (v/v, 2:1) as green solvent. All synthesized products are furnished in good yields in the short reaction time, and then their structures were confirmed by NMR, mass spectrometry and X-ray crystallography analysis.

Selective and reversible 1,3-dipolar cycloaddition of 6-aryl-1,5-diazabicyclo[3.1.0]hexanes with 1,3-diphenylprop-2-en-1-ones under microwave irradiation

The first example of the cycloaddition of in situ-generated azomethine imine under microwave conditions is described. The reaction of 6-aryl-1,5-diazabicyclo[3.1.0]hexanes with 1,3-diphenylprop-2-en-1-ones proceeds regio- and stereoselectively giving mostly good yields of the corresponding perhydropyrazolopyrazoles. The products of the reaction undergo cycloreversion under the reaction conditions.

Ambient access to a new family of pyrrole-fused pyrazine nitrones via 2-carbonyl-N-allenylpyrroles

The chemo-, regio- and stereoselective synthesis of pyrrole-fused pyrazine nitrones via the direct reaction of 2-carbonyl-N-allenylpyrroles (readily accessible from the corresponding NH-pyrroles) with hydroxyl amine hydrochloride has been developed.

Ultrasonic-assisted synthesis of 1,4-disubstituted 1,2,3-triazoles via various terminal acetylenes and azide and their quorum sensing inhibition

An efficient synthesis of 1,4-disubstituted 1,2,3-triazole derivatives was studied. 1,4-Disubstituted 1,2,3-triazoles containing isoxazole and thymidine structures were synthesized in 84-96% yields starting from various terminal isoxazole ether alkynes and β-thymidine azide derivatives via a 1,3-dispolar cycloaddition using copper acetate, sodium ascorbate as the catalyst under ultrasonic assisted condition. All the target compounds were characterized by HRMS, FT-IR, ¹H NMR and ¹³C NMR spectroscopy. Furthermore, the quorum sensing inhibitory activities of synthesized compounds were evaluated with Chromobacterium violaceum (C. Violaceum CV026) based on their inhibition of violacein production, with compound C₁₀-HSL as a positive control. The compounds 8a, 8c and 8f exhibited considerable levels of inhibitory activity against violacein production, and IC₅₀ values were 217±19, 223±20 and 42.8±4.5μM, respectively, which highlighted the potential of these compounds as lead structures for further research towards the development of novel QS inhibitors.