Deuteration Degree‐Controllable Methylation via a Cascade Assembly Strategy using Methylamine‐Water as Methyl Source.

We present a novel and effective photocatalytic method for the methylation of β‐diketones with controllable degrees of deuterium incorporation via development of new methyl sources. By utilizing a methylamine‐water system as the methyl precursor and a cascade assembly strategy for deuteration degree control, we synthesized methylated compounds with varying degrees of deuterium incorporation, showcasing the versatility of this approach. We examined a range of β‐diketone substrates and synthesized key intermediates for drug and bioactive compounds with varying degrees of deuterium incorporation, ranging from 0 to 3. We also investigated and discussed the postulated reaction pathway. This work demonstrates the utility of readily available reagents, methylamines and water, as a new methyl source, and provides a simple and efficient strategy for the synthesis of degree‐controllable deuterium‐labelled compounds. [ABSTRACT FROM AUTHOR]