From Aldehyde to Ketone via Water-Accelerated Molybdenum-Photocatalysis

The efficient “on water” protocol was developed by employing molybdenum-based polyoxometalate [N(C₄H₉)₄]₂[Mo₆O₁₉] 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.