N-Triflination of pyrazolones: a new method for N-S bond formation
Ahwan Panigrahi1, Nachimuthu Muniraj1, Kandikere Ramaiah Prabhu1
1Department of Organic Chemistry, Indian Institute of Science, Bangalore 560 012, Karnataka, India. prabhu@orgchem.iisc.ernet.in.
Abstract:
A simple method, which takes place quickly in 5 min, is developed for the N-triflination of pyrazolones using CF3SO2Na (Langlois reagent) and phenyliodine(iii)bis(trifluoroacetate) (PIFA). This reaction takes place at the imine nitrogen centre instead of the more reactive C4-position, forming a new N-S bond. A variety of pyrazolone derivatives were subjected to the reaction. Unlike the previous reports on sulfenylation or sulfonylation of pyrazolone, wherein the corresponding C-S bond is formed, this new method leads to the formation of the hetero-hetero atom bond (N-S bond) at room temperature.
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