Synthesis and Isolation of α-Diazophosphonium Ylides

Well-controlled generation and utilization of phosphorus-ylide-stabilized diazo compounds remain largely unexplored, despite their potential applications. Here, we report a general strategy that transforms Bestmann ylide derivatives into α-diazophosphonium ylide, triazole, or thiadiazole derivatives via reactions with organo-azides, enabling the first isolation of α-diazophosphonium ylide, species that combines the properties of classical ylides with diazo functionality. Its reactivity was examined with diverse E–H bonds across the p -block elements. DFT studies elucidate the factors governing product selectivity and the unique charge distribution that determines the subsequent reactivity. This work establishes α-diazophosphonium ylide as a new entry point into diazo chemistry and opens avenues for future applications in synthesis.