Safe and Scalable Continuous Flow Azidophenylselenylation of Galactal to Prepare Galactosamine Building Blocks

Differentially protected galactosamine building blocks are crucial for synthesizing human and bacterial oligosaccharides. The azidophenylselenylation of 3,4,6-tri-O-acetyl-d-galactal yields the corresponding 2-nitrogenated glycoside efficiently. However, poor reproducibility and safety concerns with traditional batch methods limit scalability. We present a safe, efficient, and reliable method for azidophenylselenylation at room temperature using continuous flow chemistry. This approach minimizes side products and drastically reduces reaction time compared to batch processes. The flow setup is scalable, processing 5 mmol of galactal in 3 hours to yield 1.2 mmol/h of product.