8-Oxabicyclo[5.1.0]octa-2,4-diene ( 1) is obtained from cycloheptatriene with commercial 40% peracetic acid. Upon catalytic and LiAlH4 reduction the allylic CO-bond in 1 is cleaved. Acid catalised hydrolysis leads to a mixture of all six possible isomeric cycloheptadienediols. With BF3 in the absence of water isomerization to 3,5-cycloptadienone is observed.