1,3-dipolar cycloadditions of 3-bromo-1,5-and 3-bromo-1,7-azulenequinones with diazomethane, diphenylnitrilimine, and benzonitrile oxide

The reactions of 3-bromo-1,5- and 3-bromo-1,7-azulenequinones with diazomet hane gave cyclooctatrienone derivatives and a [4+2] 1,3-dipolar adduct whil e they reacted with diphenylnitrilimine and benzonitrile oxide to give the corresponding [4+2] 1,3-dipolar adducts, showing the different site selecti vities. 3-Bromo-1,5-azulenequinone reacted with the 1,3-dipoles dominantly to form the adducts on the cyclopentenone part while 3-bromo-1,7-azulenequi none reacted on the seven-membered ring.