Copper-assisted palladium catalyzed the cross-coupling reaction of Alknylalane reagents with 2-Thiobenzo[d]thiazoles via C–S bond cleavage

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A highly efficient and simple route for the synthesis of 2-alknyl benzo[d]thiazoles has been developed by palladium and copper catalyzed the cross-coupling reaction of 2-thiobenzo[d]thiazoles with (hetero)aromatic and aliphatic alkynylaluminum reagents. Various 2-alkynyl benzo[d]thiazole derivatives can be obtained in 19–97 % isolated yields using 1 mol% PdCl2(dppf)/5 mol% xanthpos as the catalyst and CuI (3 equiv.) as desulfurization agent. The cross-coupling reaction can be carried out smoothly with electron-donating or -withdrawing groups on the aromatic ring of the organo aluminum reagents or the 2-thiobenzo[d]thiazoles. Furthermore, the broad substrate scope and the maintenance of high efficiency on a gram scale make this protocol a potentially practical method to synthesize 2-alkynylbenzo[d]thiazole derivatives. On the basis of the experimental results, a possible catalytic cycle has been proposed.2009 Elsevier Ltd. All rights reserved.