Strained compounds are of special interest because of their increased energy content and the enhanced reactivity that frequently results from this. The already considerable ring strain of simple cyclopropenes (ca. 54 kcalmolÀ1) is significantly increased if the three-membered ring is incorporated into the bicyclic framework 1 (Scheme 1).[1] It should be possible to transfer this concept from the hydrocarbons 1 to the heterocycles 3.[2, 3] The 2, 3-bridged ...