Base-induced elimination of dichlorocarbene adducts 2 to 9-alkoxyphen threnes 1 leads to furans 6, presumably via cyclopropenes 3 which undergo rearrangement to vinylcarbenes 4 and C-H insertion. By the same sequence, the 9-substituted alkylphenanthrene adduct 10 and 14 afford cyclopentadienes 11 and 15. Carbene adducts of simple enol ethers, however, react differently and give preferentially 2-chloroalken-2-ones.