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.
Heterocycle Formation via Palladium-Catalyzed Intramolecular Oxidative C−H Bond Functionalization: An Efficient Strategy for the Synthesis of 2-Aminobenzothiazoles
作者:Laurie L. Joyce、Robert A. Batey
DOI:10.1021/ol900958z
日期:2009.7.2
N-Arylthioureas are converted to 2-aminobenzothiazoles via intramolecular C−S bond formation/C−H functionalization utilizing an unusual cocatalytic Pd(PPh3)4/MnO2 system under an oxygen atmosphere at 80 °C. This method eliminates the need for an ortho-halo substituted precursor, instead achieving direct functionalization of the ortho-aryl C−H bond. Mechanistic observations, including a large intramolecular
Cu(<scp>ii</scp>) catalysed chemoselective oxidative transformation of thiourea to thioamidoguanidine/2-aminobenzothiazole
作者:Santosh K. Sahoo、Nilufa Khatun、Anupal Gogoi、Arghya Deb、Bhisma K. Patel
DOI:10.1039/c2ra22240j
日期:——
o-halogens (–F, –Cl) gave 2-aminobenzothiazoles via a dehalogenative heteroarylation path and not by the Hugerschoff path involving an electrophilicsubstitutionreaction. For thioureas containing reactive ortho halogens (such as –Br, –I) the reaction proceeds at room temperature giving 2-aminobenzothiazoles via a dehalogenative path requiring a catalytic quantity of Cu(II). No transformation of thiourea (Tu)
A ligand free copper(II) catalyst is as effective as a ligand assisted Pd(II) catalyst towards intramolecular C–S bond formation via C–H functionalization
作者:Arghya Banerjee、Sourav Kumar Santra、Saroj Kumar Rout、Bhisma K. Patel
DOI:10.1016/j.tet.2013.08.025
日期:2013.10
Copper(I) catalysts are usually ineffective on the other hand Pd(II) catalysts are quite effective in promoting intramolecular sp2 C–H functionalization (C–S bond formation). Herein, we have developed a ligand assisted Pd(II) catalyzed C–S bond formation via C–H activation from arylthioureas leading to the formation of 2-aminobenzothiazoles for substrates bearing electron donating (EDG) groups in the