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Ligandless Palladium-Catalyzed Regioselective Direct C-H Arylation of Imidazo[1,2-a]imidazole Derivatives
Sandrine Grosse1, Christelle Pillard2, Stéphane Massip3
1Institut de Chimie Organique et Analytique (ICOA), Université d'Orléans, UMR-CNRS 7311 , BP 6759, rue de Chartres 45067 Orléans Cedex 2, France.
Abstract:
Herein a novel access to functionalizable 6-substituted imidazo[1,2-a]imidazole scaffolds is described. The reactivity of this heterobicyclic unit toward direct C-H arylation was studied, and conditions allowing regioselective arylation at position 3 were successfully developed. The practicability of this method is manifested by the ligandless conditions and low catalyst loading. The strategy is functional group tolerant and provides rapid access to a large variety of 3,6-di(hetero)arylated imidazo[1,2-a]imidazole derivatives. A second arylation at position 2 was then carried out, and a library of diversified 2,3,6-tri(hetero)arylated imidazo[1,2-a]imidazoles was generated in good yields. A one-pot, two-step procedure was finally developed.
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