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Oxidative Carbon−Carbon Bond Cleavage of a [2.2]Paracyclophane Derivative − Efficient Intramolecular Trapping of the Radical Cation
Author(s) -
Sankararaman Sethuraman,
Hopf Henning,
Dix Ina,
Jones Peter G.
Publication year - 2000
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/1099-0690(200008)2000:15<2711::aid-ejoc2711>3.0.co;2-b
Subject(s) - chemistry , intramolecular force , cycloaddition , substituent , bond cleavage , aryl , nitromethane , photochemistry , medicinal chemistry , carbon–carbon bond , ring (chemistry) , radical ion , stereochemistry , lewis acids and bases , organic chemistry , catalysis , ion , alkyl
4‐(2,3,4,5‐Tetraphenyl)phenyl[2.2]paracyclophane ( 3 ) has been prepared by cycloaddition of tetracyclone ( 2 ) to 4‐ethynyl[2.2]paracyclophane ( 1 ). On treatment with FeCl 3 or AlCl 3 or NOBF 4 in nitromethane, 3 undergoes C−C bond cleavage by an electron transfer process to provide the double benzyl radical cation 10 . The phenyl groups of the aryl substituent are ideally oriented for intramolecular trapping and, in the presence of the Lewis acids, ring closure to the new phane system 5 takes place in good yield (65%). In the presence of NOBF 4 , the half‐cyclized aldehyde 6 (66%) is produced. For comparison, [2.2]paracyclophane ( 7 ) was also treated with the latter one‐electron oxidant, providing bibenzyl‐4,4′‐dicarbaldehyde ( 8 , 30%) and its monooxime 9 (35%). The structures of the new phane systems 3 and 5 have been determined by X‐ray structural analysis, and the mechanisms leading to these products are discussed.