Eco-friendly atom-economical synthesis of 2-substituted-benzo[d]thiazoles and 2-substituted-benzo[d]oxazoles using 2-acylpyridazin-3(2H)-ones

Recent Progress in the Chemistry of Pyridazinones for Functional Group Transformations

“…The tautomerization depends on the solvent’s dielectric constant and the electronic structure (e.g., the electron-donating vs electron-withdrawing groups) of substituents on the pyidazin-3­(2 H )-one. Since pyridazin-3­(2 H )-one readily forms the stable anion, stabilized by the resonance, it could act as a good leaving group. − Pyridazin-3­(2 H )-ones are also the ambient anions under basic conditions. , The regioselectivity of their N - and O -alkylations depends on the nature of the base, the structure of alkyl halide, the substituents on the heterocycle, and the reaction conditions such as temperature and solvent. , Pyridazin-3­(2 H )-ones can be easily removed and isolated for reuse during synthetic processes.…”

“…Ecofriendly and atom-economical synthesis of 2-substituted benzo­[ d ]­thiazole and 2-substituted benzo­[ d ]­oxazoles using 3 has been reported . The reaction of 2-aminothiophenols with 3 under catalyst-free and neutral conditions affords the corresponding 2-substituted benzo­[ d ]­thiazoles in 50–94% yields (Scheme ).…”

Eco-Friendly Syntheses of 2-Substituted Benzoxazoles and 2-Substituted Benzothiazoles from 2-Aminophenols, 2-Aminothiophenols and DMF Derivatives in the Presence of Imidazolium Chloride

“…2-(4-Methoxyphenyl)benzo[d]thiazole ( 4e ) [21]: The product was obtained as white solid in 87% yield. m.p.…”

“…Since these reports, many improvements to these reactions have been made by the use of alternative catalysts. In 2013, Yoon et al [21] reported an improved method to form benzimidazoles using 2-acyl-4,5-dichloropyridazin-3(2 H )-one as acyl transfer agent under transition-metal-free conditions, (Scheme 1a), but, this reagent is expensive and additional POCl 3 is needed. Liu and Chung have reported [22,23,24] the synthesis of benzothiazoles from 2-aminobenzenethiol using silane as a CO 2 fixing agent.…”

Benzothiazoles from Condensation of o-Aminothiophenoles with Carboxylic Acids and Their Derivatives: A Review

“…The synthesis of several substituted BTs 87 in 50-94% yields was carried out from the condensation of substituted ATPs with 2-acylpyridazin-3(2H)-ones as acyl transfer agents under transition-metal-free and eco-friendly conditions. The reaction was efficient, green, and economical, with several applications in organic synthesis and in medicinal and industrial chemistry (Scheme 67) [175].…”