An Azide-Free\nSynthesis of Metallodiazomethanes Using\nNitrous Oxide

Diazo compounds are\nvaluable reagents in synthesis but usually\nrequire the use of potentially explosive or toxic starting materials.\nHere, we report the synthesis and isolation of alkali metal diazomethanides\nby the reaction of metalated ylides with nitrous oxide, resulting\nin a formal exchange of the phosphine ligand by dinitrogen. The reaction\nproceeds through a Wittig-like mechanism via a [3 + 2] cycloaddition\nof N<sub>2</sub>O across the ylide bond with release of phosphine\noxide. The metalated diazomethanes exhibit an increased thermal stability\ndue to the stronger binding of N<sub>2</sub> compared to neutral diazomethanes.\nThis is reflected in short C–N distances and red-shifted N–N\nvibrations and enables versatile applications such as for the preparation\nof transition metal diazomethanide complexes and the synthesis of\n1,2,3-triazoles from nitriles, diazoacetates from carbon dioxide,\nor alkynes from aldehydes.