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Abstract
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The Mizoroki–Heck reaction,1 palladium-catalyzed olefination of aryl halides, has become one of the most powerful methods for carbon–carbon bond formation in organic synthesis.2-3 Phosphine ligands are commonly used in the Heck reaction, which suffer from some disadvantageous such as environmental problems, moisture and air-sensitivity, high toxicity and cost of phosphine ligands. Therefore, the development of new phosphine-free catalytic systems for Heck reaction would be an interesting subject, which among them imidazoles play an important role. Recently, we have reported Heck reaction using PdCl2/3-aroyl-4(5)-arylimidazole catalytic system, which afforded corresponding Heck products in good to excellent yields.4 The results encouraged us to work on the Heck reaction using easily prepared and air and moisture stable 5,6-diphenyl-3-(pyridin-2-yl)-1,2-4-triazine I, which was prepared by cyclocondensation of 2-pyridylamidrazone with benzil in EtOH under reflux condition. 2-Pyridylamidrazone was synthesized by heating a solution of hydrazine with pyridin-2-carbonitrile in EtOH.
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