Construction of Highly Functionalized C4-Oxyacylated and Aminated Pyrazolines
Vikram Singh1, Bal Krishna Mishra1, Deepak Kumar1
1Department of Biological and Synthetic Chemistry, Centre of Biomedical Research, SGPGIMS-Campus, Raebareli Road, Lucknow 226014, India.
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Pyrazolines and pyrazolones are prevalent cores in drugs and bioactive molecules. Functionalizing them with heteroatoms on the ring improves or expands their clinical efficacy. However, a general method to selectively heterofunctionalize them at C4 and C5 is still elusive. Herein, we have demonstrated an iodine(III)-mediated construction of C4-heterofunctionalized pyrazolines from α,β-unsaturated hydrazones. The oxyacylated and aminated products, bearing a tertiary as well as a secondary stereocenter, were obtained via aza-Michael, followed by a C-O/C-N bond formation. A deprotection/oxidation sequence produced pyrazolones in a quantitative yield.
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