An “on-water” exploration of CuO nanoparticle catalysed synthesis of 2-aminobenzothiazoles
作者:Saroj Kumar Rout、Srimanta Guin、Jayashree Nath、Bhisma K. Patel
DOI:10.1039/c2gc35575b
日期:——
An âon-waterâ one-pot process has been engineered for the preparation of 2-aminobenzothiazole from ortho-halo (âF, âCl, âBr and âI) substituted unsymmetrical thioureas. For ortho âI and âBr substrates the reactions afford 2-aminobenzothiazoles under metal free condition promoted by base. However, the relatively inert ortho âCl and âF substrates undergo intramolecular arylthiolation only in the presence of CuO nanoparticles yielding 2-aminobenzothiazoles. This methodology provides easy access to aminobenzothiazoles utilising even the ortho âCl and âF substrates. The catalyst is recyclable several times without loss of substantial activity. Other remarkable features include the wide range of functional group tolerance, absence of chromatographic purification (for ortho âI and âBr substrates) and providing moderate to excellent yield of the products under mild conditions, thus rendering the methodology as a highly eco-friendly alternative to the existing methods.
一种“水上”一锅法被设计用于从邻卤素(-F、-Cl、-Br和-I)取代的不对称硫脲制备2-氨基苯并噻唑。对于邻-I和邻-Br底物,反应在无金属的条件下,在碱的促进下生成2-氨基苯并噻唑。然而,相对惰性的邻-Cl和邻-F底物仅在存在CuO纳米颗粒的条件下进行分子内芳香硫化反应,生成2-氨基苯并噻唑。该方法为利用邻-Cl和邻-F底物提供了简便的氨基苯并噻唑合成途径。催化剂可多次回收使用,且活性无显著下降。其他显著特点包括对多种功能团的良好耐受性、邻-I和邻-Br底物不需要进行层析纯化,以及在温和条件下提供中等至优良的产物收率,从而使该方法成为现有方法的高度环保替代品。