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The Expedient and Regioselective Metalation of Unprotected Biphenyl‐2‐, ‐3‐, and ‐4‐carboxylic Acids
Author(s) -
Tilly David,
Samanta Subhendu S.,
Castanet AnneSophie,
De Asish,
Mortier Jacques
Publication year - 2006
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/ejoc.200500469
Subject(s) - metalation , chemistry , regioselectivity , butyllithium , carboxylic acid , biphenyl , carboxylate , medicinal chemistry , benzene , organic chemistry , electrophile , catalysis
Unprotected biphenyl‐2‐carboxylic acid can be cleanly metalated with sec ‐butyllithium at the position adjacent to the carboxylate and can then be subjected to site‐selective electrophilic substitution. The remote C2′‐position is attacked by the superbasic mixture of n ‐butyllithium and potassium tert ‐butoxide (LICKOR, 3.5 equiv.) in THF or benzene at 20–60 °C. The resulting dianion cyclizes to give the fluorenone skeleton. The metalation reactions of biphenyl‐3‐ and ‐4‐carboxylic acids are also described. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)