Regiochemistry of Halogen Azide Addition to Allenes

Iodine azide was found to undergo monoaddition to alkyl-substituted allenes 8–11, producing regioselectively allyl azides that can undergo [3,3]-rearrangement. Allene itself is an exception and adds IN₃ at room temperature to form a bisadduct, shown to have a gem-diazide structure and to be derived from a vinyl azide monoadduct. BrN₃ tends to behave as an ionic reagent analogous to IN₃ at –65 °C, but at room temperature it adds to allenes in a free radical manner, leading to bisadducts which are unstable and can decompose explosively. The chemistry of the adducts was briefly explored.