Synthesis and Comparison of the Reactivity of Allyl Fluorides and ...

6.5.7 Preparation of 2,2-difluoro-1-phenylbut-3-enyl 4-methylbenzoate (164)
188
Chapter Six
The title compound was prepared using a method
outlined by Nakamura et al. [7] A 100 cm 3 , two-necked
round-bottomed flask was equipped with a magnetic
stirring bar, and Rotaflo tap and attached to a Schlenk
line. After flame-drying under high vacuum, the flask
was cooled and filled with nitrogen. The reaction flask
was charged with 2,2-difluoro-1-phenylbut-3-en-1-ol
(0.05 g, 0.27 mmol) and pyridine (1 cm 3 ) and cooled to 0 ºC. 4-methylbenzoyl chloride
(0.03 cm 3 , 0.26 mmol) was added and the reaction mixture warmed to room temperature and
stirred for 4 h. After which the reaction was quenched with brine (5 cm 3 ) and diethyl ether
(5 cm 3 ). The organic layer was then separated and washed with HCl (1 cm 3 , 5 % aqueous
solution), saturated brine (10 cm 3 ), saturated NaHCO3 (10 cm 3 ) and saturated brine (10 cm 3 )
successively, then dried over magnesium sulphate. After removal of solvent in vacuo the
crude product was purified by column chromatography [chloroform: hexane (30:70)],
affording the product as an oil (16 mg, 20 %). δH 5.44 (1H, d, 3 JHH = 11.0 Hz, Hb), 5.62
(1H, ddt, 3 JHH = 17.2 Hz, 4 JHF = 2.7 Hz, 2 JHH = 0.8 Hz, Ha), 5.86 (1H, ddt, 3 JHH = 17.2 Hz,
3 JHF = 11.4Hz, 3 JHH = 11.0 Hz, Hc), 6.13 (1H, ap.t, 3 JHF = 9.8 Hz, CHO), 7.20 (2H, d, 3 JHH =
8.2 Hz, ArH-3), 7.27-7.32 (3H, m, ArH’), 7.40-7.45 (2H, m, ArH’), 7.93 (2H, dm, 3 JHH = 8.2
Hz, ArH-2); δC 21.7 (CH3), 75.6 (t, 3 JCF = 30.2 Hz, CHCF2), 118.2 (t, 1 JCF = 244.0 Hz, CF2),
121.9 (t, 3 JCF = 8.8 Hz, CHCH2), 126.7 (ArC-1), 128.2 (ArCH-3’), 128.3 (ArCH-2’), 129.1
(ArCH-4’), 129.3 (ArCH-3), 129.9 (t, 2 JCF = 26.1 Hz, CHCH2), 130.0 (ArCH-2), 133.5
(ArC-1), 144.4 (ArC-4’), 164.8 (C=O); δF -106.0 (d, 2 JFF = 249.1 Hz, CF), -109.2 (1F, d, 2 JFF
= 249.1 Hz, CF). m/z (EI + ) 302 ([M] + , 5 %) 119 ([M-OCH(C6H5)CF2CH=CH2] + , 100 %).
HRMS (EI) 302.11153 (C18H16O2F2 requires 302.11144).
6.5.8 Preparation of (1-(benzyloxy)-2,2-difluorobut-3-enyl)benzene (165)
The title compound was prepared using a method outlined by
Wu et al. [22] A 100 cm 3 , two-necked round-bottomed flask
was equipped with a magnetic stirring bar, dropping funnel
and Rotaflo tap and attached to a Schlenk line. After flame-
drying under high vacuum, the flask was cooled and filled
with nitrogen. The flask was charged with a suspension of
NaH in anhydrous DMF via syringe, and stirred at 0 ºC. 2,2-difluoro-1-phenylbut-3-en-1-ol