Modified reaction conditions to achieve high regioselectivity in the two component synthesis of 1,5-diarylpyrazoles

The factors affecting regioselectivity during the formation of 1,5-diarylpyrazoles from aryl hydrazines and 1,3-diketones are identified and the regioisomers were characterized by 1D NOESY, LC-NMR and X-ray analyses. A simple alteration in the usual reaction conditions is reported, which allows the exclusive formation of 1,5-diarylpyrazoles. (C) 2004 Elsevier Ltd. All rights reserved.