Synthesis of N-Hydroxyindole Derivatives via Pd-Catalyzed Electrophilic Cyclization

摘要

Heterobiaryl compounds are important building blocks that are frequently found in pharmaceuticals, natural products, organic functional materials, and chiral ligands.1 In this regard, C—H/C—H aryl coupling reactions have received intense attention recently,2 as they obviate the need for pre-functionalization of coupling partners (C-M or C-X). For the coupling of two nucleophilic (hetero)arenes, methods based on internal oxidants, i.e., pre-functionalization of substrates with oxidizing groups, may provide an enhanced level of selectivity over external-oxidant-based approaches (Scheme 1(a) vs. 1(b)). For example, Proctor and coworkers have utilized benzothiophene S-oxides that can function as an electrophilically modified thiophene for heterobiarylation. or electrophilic activators of phenols for subsequent homo- and heterocoupling.