Turning light into carbinols: a metal-free radical strategy for pyridine based triaryl scaffolds

Abstract

Triaryl carbinols are key building blocks in pharmaceuticals, agrochemicals, and functional materials, yet their synthesis typically relies on hazardous organometallic reagents or costly transition-metal catalysts. Here we report a metal-free, light-driven strategy for their preparation under mild and sustainable conditions. The method exploits the dual role of 2-propanol, which acts as a hydrogen donor in the photomediated HAT process with benzophenone, while the resulting ketyl radical selectively reduces 4-cyanopyridines via electron transfer, enabling a radical–radical coupling that furnishes triaryl carbinols in a single step. The protocol delivers excellent yields (up to 99%) across a broad substrate scope, encompassing diverse benzophenones and pyridines. Its robustness was demonstrated in batch, flow, and under simulated sunlight, and the methodology enabled the efficient synthesis of analogues of bioactive molecules of pharmaceutical relevance. Notably, the optimized protocol scores >80 on the EcoScale (indicating excellent sustainability in terms of reagent safety, energy input, and workup efficiency). This work establishes a versatile and greener platform for the synthesis of triaryl carbinols with strong potential for industrial and medicinal applications.