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Dehydrative Fragmentation of 5-Hydroxyalkyl-1H-tetrazoles: A Mild Route to Alkylidenecarbenes

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journal contribution
posted on 16.03.2012, 00:00 by Duncan J. Wardrop, John P. Komenda
The development of a mild, base-free method for the generation of alkylidenecarbenes is reported. Treatment of 5-hydroxyalkyl-1H-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 2 mol of dinitrogen. Details of this methodology, its application to the synthesis of combretastatin A-4, and an improved route to 5-hydroxyalkyl-1H-tetrazoles are described.