Synfacts 2008(8): 0865-0865  
DOI: 10.1055/s-2008-1078603
Metal-Mediated Synthesis
© Georg Thieme Verlag Stuttgart ˙ New York

Selective Functionalization of Pyrazoles Using a Switchable Metal-Directing Group

Contributor(s): Paul Knochel, Tobias Thaler
M. McLaughlin*, K. Marcantonio, C.-y. Chen, I. W. Davies
Merck Research Laboratories, Rahway, USA
Further Information

Publication History

Publication Date:
23 July 2008 (online)

Significance

A regiocontrolled functionalization of pyrazoles was achieved by sequential lithiation of the 3- and 5-position using a switchable metal-directing group (THP). Halogenation of the 4-position with NBS and subsequent cross-coupling led to a fully functionalized 3,4,5-trisubstituted pyrazole.