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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)


Abstract

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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Regioselective Synthesis of 1,3,5-Tri- and 1,3,4,5-Tetrasubstituted Pyrazoles from N-Arylhydrazones and Nitroolefins

X. Deng, N. S. Mani, J. Org. Chem., 2008, 73, 2412-2415.

Reaction of N-Monosubstituted Hydrazones with Nitroolefins: A Novel Regioselective Pyrazole Synthesis

X. Deng, N. S. Mani, Org. Lett., 2006, 8, 3505-3508.


Key Words

pyrazoles


ID: J54-Y2008-0830