The reactive bicyclo[n.1.0]alk-1(omega)-enes (n = 3-6) 9a-d are formed by dehydrochlorination of 8a-d and trapped by diphenylisobenzofuran as exo Diels-Alder adducts 10a-d. With 8c the major adduct, 18 results not from interception of 9c but from diene 16 that is formed by dehydrochlorination/rearrangement sequences. Attempted interception of cyclopropenes 9a-d by furan provides a [4 + 2] product 19 from 9b (n = 4) only. Under the conditions employed, 9a (n = 3) ring expands to carbene prior to furan trapping while homologues 9c and 9d (n > 4) rearrange and lose HCl to give 17 and 20, respectively, without intervention of furan. 7-Chlorobicyclo[4.1.0]hepta-1(7),3-diene is likewise captured by diphenylisobenzofuran as 13.