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

6.5.13 Preparation of 2,2-difluorobut-3-enyl 2-fluorobenzoate (178)
192
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-difluorobut-3-en-1-ol (ca. 0.05 g in 40 cm 3 DCM,
0.49 mmol) and pyridine (1 cm 3 ) and cooled to 0 ºC. 2-fluorobenzoyl chloride (0.4 cm 3 ,
2.45 mmol) was added and the reaction mixture stirred at 0 ºC for 4 h. After which the
reaction was quenched with brine (5 cm 3 ) and the organic layer separated and washed with
HCl (10 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 (50:50)], affording the product as an oil (35 mg, 25 %). δH 4.49 (2H,
ap.t, 3 JHF = 12.1 Hz, CHO), 5.51 (1H, d, 3 JHH = 11.0 Hz, 2 JHH = 0.8 Hz, Hb), 5.73 (1H, ddt,
3 JHH = 17.6 Hz, 4 JHF = 3.1 Hz, 2 JHH = 0.8 Hz, Ha), 5.96 (1H, ddt, 3 JHH = 17.6 Hz, 3 JHF = 11.3
Hz, 3 JHH = 11.0 Hz, Hc), 7.18 (1H, m, ArH-3), 7.25 (1H, m, ArH-5), 7.59 (1H, m, ArH-4),
7.98 (1H, m, ArH-6); δC 64.7 (t, 2 JCF = 32.1 Hz, OCH2), 117.2 (d, 2 JCF = 24.1 Hz, ArCH-3),
117.6 (t, 1 JCF = 240.9 Hz, CF2), 121.7 (t, 3 JCF = 10.0 Hz, CHCH2), 124.1 (d, 4 JCF = 4.0 Hz,
ArCH-5), 130.0 (t, 2 JCF = 26.1 Hz, CHCH2), 132.2 (ArCH-6), 134.5 (d, 2 JCF = 10.0 Hz, ArC-
1), 135.1 (d, 3 JCF = 10.0 Hz, ArCH-4), 162.12 (d, 1 JCF = 253.0 Hz, ArCF), 163.2 (C=O); δF, -
105.7 (2F, s, CF2), -108.6 (1F, s, CF). m/z (EI) 230 (M + , 12 %), 123 ([M-
OCH2CF2CH=CH2] + , 100 %). HRMS (EI) 230.05519 (C11H9O2F3 requires 230.05524).
6.5.14 Preparation of 2,2-difluorobut-3-enyl 4-methylbenzoate (180)
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-difluorobut-3-en-1-ol (ca.
0.05 g in 40 cm 3 DCM, 0.49 mmol) and pyridine (1 cm 3 ) and cooled to 0 ºC. 4-
methylbenzoyl chloride (0.3 cm 3 , 2.45 mmol) was added and the reaction mixture stirred at
0 ºC for 4 h. After which the reaction was quenched with brine (5 cm 3 ) and the organic