The sequence of rearrangements of carbenes 6 has been studied. Precursors for 6 were l-halo-a(n-halomethyl)bicyclo[1:1.1]pentane derivatives 11, which were obtained by addition of polyhalomethanes to the central bond of [1.1.1]propellane derivative 13 via radical chain processes. Reaction of compounds 11 with MeLi or sodium bis(trimethylsilyl)amide generates carbenes 6, which are stabilized by a carbene (6)bridgehead olefin-carbene (9) rearrangement, followed by an intramolecular CH insertion reaction of carbenes 9 to afford tetracyclononane derivatives 15 in good yields. The carbenes 6 show only slight preferences in the rearrangement to alkenes 7 and 8. Both could be trapped with alpha-methylstyrene as ene adducts 16 and 17. The strongly twisted bridgehead olefin 7 has only the option to rearrange to carbene 9, whereas 8 could give 9 or 10, but prefers to give 9, in accordance with results of DFT calculations. The tetracyclononanes 15e and 15d contain halide atoms in the 1,3-positions; on treatment with t-BuLi both compounds form a new CC bond by reductive dehalogenation giving rise to the formation of a [2.1.1]propellane derivative 23 as short-lived intermediate.