Pd-catalyzed C—H arylation of N-sulfonyl indole derivatives
The sulfonyl-directing group guided and palladium catalyzed selective C—H arylation of N-p-toluenesulfonyl indole was investigated using iodoaromatic hydrocarbons as arylation reagent.The results showed that N-p-toluenesulfonyl indole could be converted into 2-and 2,7-arylated products with an overall yield of 93%in 1,4-dioxane at 120℃for 24 h with palladium acetate as catalyst,triphenylphosphine as ligand,Na2CO3 as base and Ag2CO3 as additive.Under these optimized conditions,the applicability and limitation of the synthetic method were examined by changing the structure of the reaction substrate and aryl iodides.As a result,28 indole-based compounds with overall yields ranging from 22%～93%were synthesized,and characterized by 1HNMR,13CNMR and HRMS spectra for structure confirmation.
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