Here, we report a metal-free cross-coupling reaction of diazines and related heteroarenes with organoboron species via C–H functionalization. The optimized conditions represent a metal-free method for the activation of aryl/heteroarylboronic acids, which undergo coupling with diazines and related heteroarenes. Optimized conditions also find application in the synthesis of a pyrimidine-based potent CDK inhibitor, meriolin1.