A flexible route to [4.1.1]propellanes

Reaction of Diels-Alder adducts of 1-bromo-2-bromomethylcyclopropene and ei ther 1,3-dienes or furans with n- or t-butyllithium leads to a 1,3-dehaloge nation to produce [4.1.1]propellanes. The oxygen bridged propellane derived from furan reacts with a second mole equivalent of n-butyllithium by cleav age of the bridge with allylic rearrangement and the formation of a cis-2-b utyl[4.1.1]propell-3-en-1-ol. Iodination of this leads to rearrangement wit h the production of 6-methylene-8-oxabicyclo[3.2.1]oct-2-enes. The correspo nding adducts of 1-bromo-2-bromoethylcyclopropene do not undergo 1,4-debrom ination under the conditions examined. (C) 2000 Elsevier Science Ltd. All r ights reserved.