Intrinsic relative nucleophilicity of indoles

The range of applicability of intrinsic (i.e., electronic) relative indices for quantifying electrophilicity and nucleophilicity responses (Chamorro et al. in J Phys Chem A 117(12): 2636-2643, 2013) is extended to the characterization of coupling reactions of indoles with benzhydrylium ions and with the strongly electron-deficient heteroarene 4,6-dinitrobenzofuroxan. The reactivity categorization based on experimental kinetic evidence for such a electrophile/nucleophile coupling (Lakhdar et al. in J Org Chem 71(24): 9088-9095, 2006) is rationalized in terms of purely electronic descriptors, revealing the polar nucleophilic activation of indole as a key factor associated with the initial rate-determining C-C coupling process.