Abstract 4, 5-Dehydrotropone reacted with 4-phenyl-, 5-methyl-4-phenyl-, and 2, 5-dimethyl- 4-phenyloxazol to give, involving facile loss of benzonitrile from the corresponding Diels- Alder adducts, furo-[3, 4-d] tropone and its 1-methyl and 1, 3-dimethyl derivative, respectively. Protonation of furo [3, 4-d]-tropones yielded delocalized 6-hydroxy-3- oxaazulenium ions.