Fe/S-Catalyzed synthesis of 2-benzoylbenzoxazoles and 2-quinolylbenzoxazoles via redox condensation of o-nitrophenols with acetophenones and methylquinolines

Annulative coupling of sulfoxonium ylides with 2-amino(thio)phenols: easy access to 2-acyl benzox(thio)azoles

A novel method for synthesizing 2-acyl benzothiazoles and benzoxazole derivatives has been developed via the annulative coupling of sulfoxonium ylides with 2-aminobenzenethiol and 2-aminophenol derivatives, respectively. This metal-free, one-pot protocol employs elemental sulfur as a mediator to efficiently construct C-N, C-S, or C-O bonds and demonstrates a broad range of functional group compatibility. The potential utility of this approach is further demonstrated through large-scale reactions and the synthesis of some bioactive compounds.

Sulfur- and DABCO-Promoted Reaction between Alkylidene Rhodanines and Isothiocyanates: Access to Aminoalkylidene Rhodanines

In this work, an efficient sulfur- and DABCO-promoted reaction for the synthesis of aminoalkylidene rhodanines from available alkylidene rhodanines and isothiocyanates is reported. A tandem process including sulfurative annulation/ring-opening by liberation of a CS2 molecule/olefination allows the synthesis of aminoalkylidene rhodanines with acceptable functional group tolerance. Chemo- and stereoselectivity, operational simplicity, and synthetically useful yields are some highlighted advantages of these transformations.

Three-Component Reaction between 3-Acetylcoumarins, Amines, and Elemental Sulfur: A Designed Approach to 3-Amino-4H-thieno[3,2-c]coumarins

In this work, a series of novel 3-amino-4H-thieno[3,2-c]coumarins were designed and synthesized by a one-pot, catalyst-free, and three-component reaction of 3-acetylcoumarins with amines and elemental sulfur. Readily available starting materials, simple heating conditions, facile installation of a sulfur atom into the molecule using S8 as a sulfur source, acceptable functional group tolerance, and synthetically useful yields are some highlighted benefits of this process.

Utilization of 2-nitrophenols in annulations with aryl isothiocyanates towards the synthesis of 2-aminobenzoxazoles

A method for the annulation of 2-nitrophenols with aryl isothiocyanates is reported. The reactions proceeded in the presence of an iron(iii) acetylacetonate catalyst, elemental sulfur, NaOH as a base, and DMSO as a solvent. Derivatives of 2-aminobenzoxazoles bearing nitro, cyano, acetyl, sulfone, secondary amine, and pyrrolyl groups were successfully isolated.