Osman Ishag Adam

1 Introduction Methyl groups are present in approximately 70% of pharmaceutical compounds and play a crucial role in enhancing the physical and chemical properties of drug molecules [1]. However, the development of sustainable methods for selective heteroatom methylation has posed significant challenges over the years. Traditional methylation methods rely on activated methyl sources like methyl iodide, methyl triflate, and dimethyl sulfide, combined with excess strong base (Figure 1A) [2].