"Base effect" in the auto-tandem palladium-catalyzed synthesis of amino-substituted 1-methyl-1H-α-carbolines.

An auto-tandem Pd-catalyzed process consisting of an intramolecular direct arylation and an intermolecular Buchwald-Hartwig reaction for C-ring amino-substituted 1-methyl-1H-α-carboline synthesis has been developed. A mechanistic study of the direct arylation reaction revealed a rate effect of the inorganic base on the C-H activation step ("base effect"). The amines, reagents in the tandem protocol, appear to have a similar effect on the direct arylation.