From Aldehyde to Ketone via Water‐Accelerated Molybdenum‐Photocatalysis

The efficient “on water” protocol was developed by employing molybdenum‐based polyoxometalate [N(C 4 H 9 ) 4 ] 2 [Mo 6 O 19 ] as the photocatalyst. This water‐accelerated photoinduced process affords versatile ketones from aldehydes straightforwardly, showcasing exceptional substrate generality. Its applicability to life‐related molecules such as amino acids, peptides, and sugars, further demonstrates its potential for bioorthogonal application. The mechanistic investigation highlights the hydrogen atom transfer (HAT) process between the excited‐state POM and benzaldehyde for acyl radical formation. This highly reactive acyl radical is readily trapped by the Michael acceptor, thereby enabling subsequent C−H functionalization. Highly efficient gram‐scale flow operation underlines the industrial applicability of this transformative strategy.