THE REACTION BETWEEN 7-OXANORBORNADIENES AND TETRAARYLCYCLOPENTADIENONES - A SHORT SYNTHESIS OF 1,2,3,4-TETRAARYLBENZENES

Highly arylated benzenes cannot generally be synthesized by sequences involving electrophilic aromatic substitution. On the other hand, cycloaddition reactions work quite well for the synthesis of such systems. One of the best-known examples of this strategy is the condensation between furan and benzyne to afford adduct 1, which then undergoes conversion to 1-naphthol upon treatment with acid.1 A large number of variants upon this process have been reported; notable recent examples involve the use of bisarynes,2 bisisobenzofurans,3 and bisendooxides2a’4such as 2 and 3, or higher arynes such as naphthalyne5 to construct more complex ring systems. Another type of cy-cloaddition, which has proved useful for the synthesis of highly arylated arenes, involves thermal condensation of tetraphenylcyclopentadienone (tetracyclone, 4a) with suitable alkynes6 or arynes7 to afford 1,2,3,4-tetraaryl-benzenes (5) and 1,2,3,4-tetraarylnaphthalenes (6). respectively. © 1990, American Chemical Society. All rights reserved.