Base-Mediated Reaction of Hydrazones and Nitroolefins with a Reversed Regioselectivity: A Novel Synthesis of 1,3,4-Trisubstituted Pyrazoles
Xiaohu Deng* and Neelakandha S. Mani
*Johnson & Johnson Pharmaceutical Research & Development, L.L.C., 3210 Merryfield Row, San Diego, California 92121, Email: xdengprdus.jnj.com
X. Deng, N. S. Mani, Org. Lett., 2008, 10, 1307-1310.
DOI: 10.1021/ol800200j (free Supporting Information)
A regioselective synthesis of tri- or tetrasubstituted pyrazoles by the reaction of hydrazones with nitroolefins mediated with strong bases such as t-BuOK exhibits a reversed, exclusive 1,3,4-regioselectivity. Subsequent quenching with strong acids such as TFA is essential to achieve good yields. A stepwise cycloaddition reaction mechanism is proposed.
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X. Deng, N. S. Mani, J. Org. Chem., 2008, 73, 2412-2415.
X. Deng, N. S. Mani, Org. Lett., 2006, 8, 3505-3508.