Synthesis and Diels-Alder Reactions of 1,2-Dimethylene- and 1,2,9,10-Tetramethylene-[2.2]paracyclophane: New Routes to Bridge-Anellated[2.2]Paracyclophanedienes

The title compounds 8 and 1 have been synthesized in three steps each from 1,2-dibromo[2.2]paracyclophan-1-ene (2) and 1,2,9,10-tetrabromo[2.2]paracyclophane-1,9-diene (4), respectively. Copper-mediated coupling of vinyl bromides 2 and 4 with methyl- and phenylmagnesium bromide gives substituted [2.2]paracyclophanes 3-CH3, 3-Ph, 5-CH3, and 5-Ph in good yields. The high reactivity of the [2.2]paracyclophane-1,2-dimethylene moieties in 8 and 1 in Diels-Alder reactions has been verified in cycloadditions with p-benzoquinone to give 10 and 13 and with naphthalene 1,4-endoxide to yield 12