Elemental sulfur mediated cyclization via redox strategy: Synthesis of benzothiazoles from o -chloronitrobenzenes and benzyl chlorides

Recent Advances in the Synthesis of Heterocycles via Reactions Involving Elemental Sulfur

“…The generality of this transformation was recently demonstrated with benzaldehydes, benzyl alcohols, dibenzyl disulfide, phenylglycine, mandelic acid, phenylglyoxalic acid [104] as well as benzyl chlorides (Scheme 82). [105] In the last case with benzyl chlorides, N-methylpiperidine was used as solvent, in which one equivalent was involved in the generation quaternary N-benzylated piperidinium, which underwent next the redox condensation with o-chloronitrobenzene substrates.…”

Construction of 2-Arylbenzo[4,5]thieno[2,3-d]thiazole Skeleton via CuCl/S-Mediated Three-Component Reaction

“…As shown above, the construction of the S-containing polyheterocyclic ring systems often relied on the introduction of sulfur atom by a variety of sulfur sources including potassium thiosulfate, potassium sulfide, DMSO, potassium ethylxanthate, − the use of elemental sulfur as sulfur source is undoubtedly highly desirable owing to its inexpensive, nontoxic, inodorous, and stable characteristics. − In this communication, we report a one-pot protocol for a convenient assemblage of the 2-arylbenzo­[4,5]­thieno­[2,3- d ]­thiazole framework using elemental sulfur as sulfur source. To the best of our knowledge, this could represent the first synthesis of aryl substituted benzo­[4,5]­thieno­[2,3- d ]­thiazole up to date.…”

Facile Preparation of Benzoxazoles from S8‐Promoted Cyclization of 2‐Nitrophenols with Arylmethyl Chloride

“…Based on the forgoing reports and the control experiments,,, we proposed possible mechanisms for the formation of 3 (scheme ). 2 a can easily react with pyridine to give 1‐benzylpyridinium chloride 4 which couples with sulfur to form benzyl sulfur ether I. I evolutes sulfur and attacks at the NO 2 group of the substrate 1 a followed by dehydration affords III via II .…”