A metal-free approach to benzazoles from arylmethyl chlorides and 2-mercaptan/2-hydroxyanilines using elemental sulfur as a traceless oxidizing agent has been developed. The reactions proceeded in good to excellent yields, exhibiting good functional groups tolerance and gram-scale ability. A key mechanistic investigation indicated that the key intermediate trisulfide 6, which was characterized by NMR, HRMS and crystal X-ray crystallography, was separated in the reaction prior to the formation of the product.
A new one-pot protocol has been developed for the facile and efficient synthesis of aza-fused polycyclic quinolines (e.g., pyrrolo[1,2-a]quinolines) by the base-catalyzed reaction of 2-formylpyrroles and 2-halophenylacetonitriles. This reaction proceeded under transition metal-free conditions and showed high functional group tolerance, with the desired products being formed in good yields.
A straightforward strategy for the synthesis of 2-arylbenzothiazoles from 2-aminothiophenol and aryl aldehydes in air/DMSO oxidant system has been developed. This reaction is operationally simple, proceeds without catalysts, tolerates a wide range of functionalities, and provides desired products in good to excellent yields.
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