Cu(II)-catalyzed sulfonylation of 7-azaindoles using DABSO as SO2-Source and its mechanistic study

Abstract

DABSO mediated sulfonylation of iodinated 7-azaindoles was achieved for the first time through sulfonylative Suzuki-Miyaura cross coupling (SMC) reaction under mild conditions giving good yields of sulfonylated 7-azaindole derivatives. Interestingly, control experiments suggest that present method involves in-situ generation of ArSO2 free radical followed by the key steps of SMC reaction. Scope of the reaction was explored with both electronically different and bulky group carrying boronic acids as coupling partner. The sulfonylation is scalable and occurred selectively at iodo group, irrespective of its position on azaindole. Moreover, the proposed mechanism has been supported by electron paramagnetic resonance (EPR) and density functional theory (DFT) calculations.