The development of a mild, base-free method for the generation of alkylidenecarbenes is reported. Treatment of 5-hydroxyalkyl-1 H-tetrazoles with carbodiimides generates products arising from the 1,2-rearrangement or [1,5]-C-H bond insertion of a putative alkylidenecarbene. Formation of this divalent intermediate is proposed to occur by way of a tetraazafulvene, which undergoes extrusion of two moles of dinitrogen. Details of this methodology, its applicationtothesynthesisofcombretastatinA-4andanimprovedrouteto5-hydroxyalkyl-1 H-tetrazolesare described.

The tetrazoles are prepared via an optimized literature procedure starting from aldehydes, ketones or ynones.

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