||Selective and Gram-Scale Synthesis of Cycloparaphenylene
Kayahara, Eiichi ,
Patel, Vijay ,
Xia, Jianlong ,
Jasti, RameshYamago, Shigeru
1619 , 2015-06-19 , Thieme Publishing Group
A selective, practical, and large-scale synthesis of cycloparaphenylene, the second smallest cycloparaphenylene to be synthesized, was achieved in nine steps starting from commercially available 1, 4-dibromobenzene and 4′-bromobiphenyl-4-ol. The key intermediate, cis-1, 4-(4-bromophenyl)-1, 4-bis(triethylsiloxy)cyclohexa-2, 5-diene, was prepared on a large scale (>20 g) and was selectively dimerized to form a cyclic precursor of cycloparaphenylene by platinum-mediated assembly and subsequent reductive elimination. Deprotection of the triethylsilyl group and subsequent tetrachlorostannic acid (H2SnCl4)-mediated reductive aromatization gave cycloparaphenylene in 23% overall yield from the commercially available substrates on gram scale.