A sonochemical method for the synthesis of 2-aminobenzimidazoles and 2-aminobenzoxazoles, as well as chiral aminooxazolines and a chiral substituted quinazolin-5-one is reported. Using the Ph3P–I2 system in the presence of triethylamine as a desulfurization agent, monothioureas prepared in situ from the reaction of bis-nucleophiles with isothiocyanates underwent rapid cyclization to afford a variety
A practical synthesis of 2-(N-substituted)-aminobenzimidazoles utilizing CuCl-promoted intramolecular cyclization of N-(2-aminoaryl)thioureas
作者:Xiao-jun Wang、Li Zhang、Yibo Xu、Dhileepkumar Krishnamurthy、Chris H. Senanayake
DOI:10.1016/j.tetlet.2004.07.042
日期:2004.9
A practical protocol for synthesis of 2-(N-substituted)-aminobenzimidazoles was developed. N-(2-Aminoaryl)thioureas undergo a CuCl-promoted intramolecular cyclization to give the corresponding 2-(N-substituted amino)benzimidazoles in good to excellent isolated yields.
Desulfurization Mediated by Hypervalent Iodine(III): A Novel Strategy for the Construction of Heterocycles
作者:Harisadhan Ghosh、Ramesh Yella、Jayashree Nath、Bhisma K. Patel
DOI:10.1002/ejoc.200800901
日期:2008.12
The desulfurization ability of diacetoxyiodobenzene (DIB) has been explored in the preparation of isothiocyanates from the corresponding dithiocarbamate salts. The in situ generated isothiocyanates reacted with o-phenylenediamine and o-aminophenol to form monothioureas, which, on treatment with a further equivalent of DIB in one pot, gave benzimidazoles and aminobenzoxazoles, respectively. Aliphatic
BOP efficiently promoted the phosphonium-mediated cyclization of thioureas, leading to a convenient synthesis of 2-aminobenzimidazoles. Compared to conventional methods, the reactions were complete at room temperature with times ranging from a few minutes to 1 h in near quantitative yields. This method is also applicable to the synthesis of more challenging structures such as 2-akylaminobenzimidazoles
One-Pot Synthesis of Five and Six Membered N, O, S-Heterocycles Using a Ditribromide Reagent
作者:Ramesh Yella、Bhisma K. Patel
DOI:10.1021/cc100124q
日期:2010.9.13
In a one-pot procedure, bromine less brominating reagent 1,1′-(ethane-1,2-diyl)dipyridinium bistribromide (EDPBT) has been utilized as an efficient desulfurizing agent for the construction of a library of heterocycles containing N, O, and S starting from aryl/alkyl isothiocyanates. In this approach, aryl/alkyl isothiocyanate reacts with o-phenylenediamine (o-PD), o-aminophenol, and o-aminothiophenol