Synthesis 2005(5): 798-803  
DOI: 10.1055/s-2005-861814
PAPER
© Georg Thieme Verlag Stuttgart · New York

The Metalation of 1- and 2-(Trifluoromethyl)naphthalenes: Noteworthy Site Selectivities

Fabrice Cottet, Eva Castagnetti, Manfred Schlosser*
Institut des Sciences Chimiques (ISIC-BCh), Ecole Polytechnique Fédérale, 1015 Lausanne, Switzerland
e-Mail: manfred.schlosser@epfl.ch;
Further Information

Publication History

Received 13 October 2004
Publication Date:
09 February 2005 (online)

Abstract

This article provides insight into the various factors by which electronegative substituents affect the kinetic acidity of arenes and, more specifically, naphthalenes. Both 1- and 2-(trifluoromethyl)naphthalenes were consecutively treated with an organometallic or lithium dialkylamide-type base and carbon dioxide. Due to single electron-transfer triggered side reactions, the yields of (trifluoromethyl)naphthoic acids were moderate to poor. 1-(Trifluoromethyl)naphthalene was exclusively attacked at the 2-position as expected. The 2-isomer reacted with tert-butyllithium in the presence of potassium tert-butoxide solely at the 1-position, but with sec-butyllithium in the presence of N,N,N′,N′-tetramethylethylenediamine concomitantly at the 3- and 4-positions. Authentic samples of the key acids 1, 4, 5 and 6 were prepared based on independent, unambiguous methods.