On the mechanism of the directed ortho and remote metalation reactions of N,N-dialkylbiphenyl 2-carboxamides.
A study concerning the mechanism of the LDA-mediated ortho and remote metalation of N,N-dialkyl-2-biphenyl carboxamides (e.g., 4a) is reported. On the basis of site-selective lithiation/electrophile quench experiments, including deuteration, the LDA metalation of 4 is proposed to involve initial amide-base complexation (CIPE) and equilibrium formation of 5, whose fast reaction with an in situ electrophile (TMSCl) to afford 6 prevents its equilibration with 7. In the absence of an electrophile, 5 undergoes equilibration via 4a with 7, whose fate is instantaneous cyclization to a stable tetrahedral carbinolamine oxide 8 which, only upon hydrolysis, affords fluorenone (3).
Tilly
David
D
Université du Maine and CNRS, Unité de Chimie Organique Moléculaire and Macromoléculaire (UMR 6011), Faculté des Sciences, avenue Olivier Messiaen, 72085 Le Mans Cedex 9, France.
Fu
Jian-min
JM
Zhao
Bao-ping
BP
Alessi
Manlio
M
Castanet
Anne-Sophie
AS
Snieckus
Victor
V
Mortier
Jacques
J
D000577:Amides / Q000138:chemical synthesis / Q000737:chemistry*; D001713:Biphenyl Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D002384:Catalysis; D003500:Cyclization; D005449:Fluorenes / Q000138:chemical synthesis / Q000737:chemistry; D015394:Molecular Structure
D000577:Amides; D001713:Biphenyl Compounds; D005449:Fluorenes; C041509:fluorene