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Paper | Regular issue | Vol 71, No. 9, 2007, pp.1967-1974
Published online, 29th May, 2007
DOI: 10.3987/COM-07-11087
Two-Stage Sonogashira Coupling Method in the Synthesis of Auxin Active Acetylenes

G. Wayne Craig,* Martin Eberle, Bruno Irminger, Anegret Schückenböhmer, Yvette Laime, and Patrick Müller

*Syngenta Crop Protection, CH-4002 Basel, Switzerland

Abstract

A sequential Sonogashira coupling of a protected acetylene precursor with aryl halides (5) followed by pyrazolyl iodides (14) allows efficient access to the unsymmetrical aryl-heteroarylacetylene (8). Subsequent regioselective lithiation exchange followed by dimethyl oxalate quench produced readily vicinal ketoesters (9) which show auxin effects in a wide variety of plant species.