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DOI: 10.1055/s-0028-1087564
Preparation of Monofluorophenols via the Reaction of Difluorobenzene Derivatives with Potassium Trimethylsilanoate
Publication History
Publication Date:
16 February 2009 (online)
Abstract
An efficient synthesis of monofluorophenols via the reaction of difluorobenzene derivatives with potassium trimethylsilanoate in moderate to excellent yields is described. High regioselectivity was observed in some cases.
Key words
fluorophenols - synthesis - regioselective - aromatic - substitution
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References and Notes
Typical Procedure
To
a N2-flushed four-necked round-bottom flask (2 L) equipped
with a mechanical stirrer, a condenser, a tem-perature controller,
and a N2 inlet, was added potassium trimethylsilanolate
(225.0 g, 1.75 mole), 1-bromo-3,5-difluorobenzene (1i,
96.5 g, 0.5 mole), and diglyme (300 mL) under N2. The
reaction mixture was heated to 120 ˚C for 5 h.
After cooling to r.t., a solution of 1 N HCl (600 mL) was added
slowly. The mixture was then extracted with TBME (1 L). The organic
extract was washed with H2O (3 × 500 mL), brine
(500 mL), dried over MgSO4, filtered, and concentrated
in vacuo to give the crude product as a reddish liquid. The crude
material was then distillated to give the pure product 3-bromo-5-fluorophenol
(4i) as a slightly yellow liquid (88.0
g, 92% yield); bp 52-55 ˚C/1.33˙10-4 bar. ¹H
NMR (300 MHz, CDCl3): δ = 5.634 (s,
1 H), 6.66-6.72 (m, 1 H), 6.78-6.82 (m, 1 H),
7.11-7.23 (m, 1 H).
¹³C
NMR (75 MHz, CDCl3): δ = 98.0 (d, J = 23.0 Hz,
1 C), 108.0 (d, J = 21.8
Hz, 2 C), 111.4 (d, J = 2.9
Hz, 2 C), 128.9 (d, J = 9.5
Hz, 2 C), 153.8 (d, J = 2.7
Hz, 1 C), 159.4 (d, J = 245.6
Hz, 1 C). ESI-HRMS: m/z calcd
for C6H4BrFO
[M + 1]+:
190.9430; found: 190.9508.