Visible‐Light‐Driven Palladium‐Catalyzed Carbonylative Cyclization to Quinolin‐2( 1 H )‐ones Using Silane as Hydrogen Donor

Comprehensive Summary Quinolin‐2(1 H )‐ones represent a class of privileged nitrogen‐containing heterocycles widely found in natural products, pharmaceuticals, and functional materials. Traditional synthetic methods often rely on harsh conditions such as high temperatures, high CO pressures, or stoichiometric oxidants, which limit their functional group tolerance and sustainability. In this work, we report a visible‐light‐driven palladium‐catalyzed carbonylative cyclization of o ‐alkynylanilines for the efficient synthesis of quinolin‐2(1 H )‐ones under mild and oxidant‐free conditions. The key innovation lies in the use of triphenylsilane (Ph₃SiH) as a mild hydrogen atom donor, enabling C–H activation and CO incorporation at ambient pressure and room temperature. The cooperative Pd(TFA)₂/Ir(ppy)₃ catalytic system, combined with TBAB as an additive, delivers the desired products in good to excellent yields with broad functional group tolerance. The protocol is applicable to a variety of substituted o ‐alkynylanilines, including those bearing electron‐donating, electron‐withdrawing, and disubstituted groups, as well as heteroaryl and cycloalkyl N ‐substituents. Notably, the method also extends to the synthesis of coumarin derivatives from o ‐alkynylphenols, further demonstrating its versatility. Late‐stage functionalization of bioactive aldehydes, such as vanillin, cinnamaldehyde, and (–)‐perillaldehyde, was successfully achieved, underscoring the potential for drug discovery applications. Gram‐scale synthesis and further transformations, including chlorination, reductive functionalization, and photocatalytic methylation, highlight the synthetic utility of this approach. Mechanistic studies, including deuterium labeling, radical trapping, and fluorescence quenching, support a radical pathway involving photoredox‐generated radical cations and Pd‐hydride intermediates. This work provides a sustainable and practical platform for the construction of valuable N ‐heterocycles and offers new insights into silane‐mediated hydrogen transfer in dual catalytic systems.