Heterogeneous Palladium Catalysts Applied to the Synthesis of 2‐ and 2,3‐Functionalised Indoles

Abstract

Abstract Heterogeneous palladium catalysts ([Pd(NH 3 ) 4 ] 2+ /NaY and [Pd]/SBA‐15) were applied to the synthesis of 2‐functionalised indoles, giving generally high conversions and selectivities (>89% yield) using only 1 mol % [Pd]‐catalyst under standard reaction conditions (polar solvent, 80 °C). For the synthesis of 2,3‐functionalised indoles by cross‐coupling arylation, the [Pd]/SBA‐15 catalyst was found to be particularly interesting, producing the expected compound with =35% yield after 12 days of reaction, which is comparable to the homogeneous catalyst, Pd(OAc) 2 (=48% yield). In the course of the study, the dual reactivity of the indole nucleus was demonstrated: aryl bromides gave clean CC coupling while aryl iodides led to a clean CN coupling.