Diazo Transfer From Nitrous Oxide Employing Phosphorus Ylides

The synthesis of diazo‐containing molecules traditionally relies on hazardous reagents such as azides or hydrazines, which restrict their practicality, especially for large‐scale applications. Herein, we report a novel strategy for diazo transfer utilizing nitrous oxide (N 2 O) fixation at a phosphorus ylide. This method enables the efficient synthesis of valuable organic building blocks under mild, hydrazine‐free conditions. The one‐pot approach provides a safer and more practical route to diazo compounds, which can be trapped directly. This facile pathway gives access to a broad range of dinitrogen‐containing compounds, including 1,2,3‐triazolo heterocycles and (macrocyclic) aldazines. We additionally disclose a new phthalazine heterocycle synthesis utilizing bis‐P‐ylides and N 2 O. Both intra‐ and intermolecular trapping are investigated, which establishes N 2 O fixation as a powerful tool in synthetic methodology.