SYNTHESIS, STRUCTURE, AND PROPERTIES OF TWOFOLD BRIDGED SESQUINORBORNENES

The twofold bridged sesquinorbornenes 2 and 6 were prepared using sequ ential [4 + 2] cycloadditions of benzoquinone with 1,5-dihydropentalen es 1 and 5. These syntheses were improved using dilution conditions or a more reactive substituted benzoquinone. Results from semiempirical and ab initio DFT calculations indicated remarkably high pyramidalizat ion angles (phi = 46-47 degrees) for the central C-C double-bond atoms . The chemical reactivity with triplet and singlet oxygen, dimethyldio xirane and N-methyl-1,2,4-triazoline-3,5-dione supports these structur al assignments.