Journal of Fluorine Chemistry 95 (1999) 121±122
SmI2 mediated Barbier reaction of a-¯uoro ethers
Rune Ringom, Tore Benneche*
Department of Chemistry, University of Oslo, PO Box 1033, Blindern, 0315 Oslo, Norway
Received 30 September 1998; accepted 25 November 1998
Abstract
Addition of a-¯uoro ethers to cyclohexanone in THF at ambient temperature has been mediated by means of SmI2. # 1999 Elsevier
Science S.A. All rights reserved.
Keywords: Barbier reaction; a-Fluoro ether; THF
1. Introduction
2. Experimental
1
The SmI2 mediated Barbier reaction has proved to be very
useful for addition of alkyl halides to the carbonyl group of
ketones [1]. The reactivity of the halides follows the usual
pattern: RI>RBr>RCl [2]. Although simple alkyl chlorides
have rather low reactivity in the SmI2 mediated Barbier
reaction, activated chlorides like a-chloro ethers react
smoothly [3±5]. Simple alkyl ¯uorides are not expected
to undergo this reaction since they are not reduced by
SmI2 even under very favourable reaction conditions [1].
In this communication we show that activated ¯uorides, i.e.
a-¯uoro ethers, react in a SmI2 mediated Barbier reaction
under mild reaction conditions.
The reaction of the a-¯uoro ethers 1a [6] and 1b [6] with
an excess of SmI2 in THF at ambient temperature in the
presence of cyclohexanone, gave the addition products 2a
and 2b in good yields (entries 1 and 2, Scheme 1). With the
a-¯uoro ether 1c [6] a 1:1 mixture of the elimination product
1,4-dihydrocoumarin and the addition product 2c was
formed (entry 3, Scheme 1).
In order to get an idea of the relative reactivity of a-¯uoro
ethers compared to other halides in this reaction, a 1:1
mixture of the a-¯uoro ether 1b and the iodide 3 was
treated with SmI2 in the presence of one equivalent of
cyclohexanone (Scheme 2). The only addition product
observed was from the a-¯uoro ether 1b. The alcohol 2b
was isolated in 51% yield together with 78% of the
unreacted iodide 3.
NMR spectra were recorded in CDCl3 at 200 MHz ꢀ H
13
and at 50 MHz ꢀ C on a Bruker DPX 200 instrument. Mass
spectra, under electron impact conditions, were recorded at
70 eV ionizing energy on a Fision ProSpec instrument. The
spectra are presented as m/z (% rel. int.).
2.1. General procedure for reaction of a-fluoro ethers with
cyclohexanone in the presence of SmI2
A solution of 1,2-diiodoethane (564 mg, 2.0 mmol) in
THF (10 ml) was added to the suspension of Sm (451 mg,
3.0 mmol) in THF (30 ml) at 08C under N2. The mixture was
stirred for 1 h before the a-¯uoro ether (1.0 mmol) and
cyclohexanone (98 mg, 1.0 mmol) in THF (10 ml) was
added. The mixture was stirred at ambient temperature
for 18 h before saturated K2CO3 solution (25 ml) was added,
and extracted with diethyl ether (3Â30 ml), dried (MgSO4)
and evaporated. The crude product was puri®ed by ¯ash
chromatography on silica gel using ethyl acetate/hexane
1:10 for elution.
1-(phenoxymethyl)cyclohexanol 2a. Oil. 1H-NMR ꢀ:
1.27±1.34 (m, 10H, CH2), 2.18 (OH), 3.80 (s, CH2),
6.87±6.99 (m, 3H, Ar), 7.23±7.32 (m, 2H, Ar).
13C NMR ꢀ: 1.7 (CH2), 25.8 (CH2), 34.3 (CH2), 70.8
(CH2), 75.3 (C), 114.6 (CH), 121.0 (CH), 129.4 (CH), 158.8
(C). MS: 206.0 (M , 8), 188 (12), 108 (65), 99 (52), 94
(100), 79 (47), 55 (29). High resolution MS: found
206.1320. Calculated for C13H18O2: 206.1307.
1-(4-chlorobenzyloxy)methylcyclohexanol
2b.
Oil.
1H-NMR ꢀ: 1.24±1.62 (m, 10H, CH2), 2.10 (OH), 3.26
*Corresponding author. Fax: +47-228-55507.
(s, OCH2O), 4.47 (s, ArCH2), 7.21±7.28 (Ar). 13C-NMR
0022-1139/99/$ ± see front matter # 1999 Elsevier Science S.A. All rights reserved.
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