Facile Syntheses of (Z)- and (E)-2,5-Dimethyl-3-styrylpyrazines, Isolated from the Argentine Ants

Abstract

Syntheses of (2)-and (E)-2,5-dimethyl-3-styrylpyrazines, isolated from Iridomyrmex humilis, were performed by replacing the chlorine atom of 3-chlaro-2,5-dimethylpyrazine with C-suhstituents, utilizing tetrakis(tripheny1phosphine)palladium as catalyst.A number of trialkylpyrazines have been isolated from mandibular gland secretions of several species of ants.'Among these pyrazines, ( Z ) -and (E)-2,5dimethyl-3-styrylpyrazines (2 and 2 ) are known as constituents of the Argentine ants, Iridomyrmex humilis.2The present paper describes briefly the syntheses of 1 and 2 by a cross-coupling reaction between 3-chlaro-2,5-dimethylpyrazine3 (3) and unsaturated compounds, such as phenylacetylene and styrene, in the presence of tetrakis(triphenylph~~phine)palladl~m. 4Recently, we have reported the dechlorinatian of the chloropyrazines and their N -~x i d e s , ~ and the introduction of the cyano group in the pyrazine ring,6 using