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

6.2.22 Preparation of 2-fluorobut-3-enyl 4-methylbenzoate (97)
151
Chapter Six
The novel compound was prepared following
the method outlined by Gouverneur et al. [8] A
100 cm 3 , three-necked round-bottom 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 flask was charged with 4-(trimethylsilyl)but-2-enyl
4-methylbenzoate (0.17 g, 0.64 mmol), anhydrous MeCN (10 cm 3 ) and Selectfluor (0.23 g,
0.64 mmol). The reaction mixture was stirred at room temperature under argon for 48 h.
After which purification by column chromatography [diethyl ether: hexane (2: 98)] afforded
the product as an oil (66 mg, 50 %). δH 2.25 (3H, s, CH3), 4.23 (1H, ddd, 3 JHF = 20.3 Hz,
2 JHH = 12.5 Hz, 3 JHH = 6.7 Hz, Hd), 4.33 (1H, ddd, 3 JHF = 26.2 Hz, 2 JHH = 12.5 Hz, 3 JHH =
3.1 Hz, He), 4.98-5.15 (1H, dm, 2 JHF = 48.9 Hz, CHF) 5.22 (1H, ap.dt, 3 JHH = 11.0 Hz, 2 JHH
= 4 JHH = 1.4 Hz, Hb), 5.35 (1H, ap.ddt, 3 JHH = 17.2 Hz, 4 JHF = 3.1 Hz, 2 JHH = 4 JHH = 1.4 Hz,
Ha), 5.80 (1H, dddd, 3 JHH = 17.2 Hz, 3 JHF = 14.3 Hz, 3 JHH = 11.0 Hz, 3 JHH = 5.9 Hz, Hc),
7.08 (2H, dm, 3 JHH = 7.8 Hz, ArH-3), 7.80 (2H, dm, 3 JHH = 8.2 Hz, ArH-2); δC 21.7 (CH3),
65.7 (d, 2 JCF = 24.1 Hz, OCH2), 90.7 (d, 1 JCF = 173.1 Hz, CHF), 119.3 (d, 3 JCF = 12.1 Hz,
CHCH2), 127.0 (ArC-1), 129.1 (ArCH-3), 129.8 (ArCH-2), 132.1 (d, 2 JCF = 19.1 Hz,
CHCH2), 144.0 (ArC-4), 166.3 (C=O); δF -185.6 (1F, s, CHF). m/z (EI + ) 208 ([M] + , 47 %)
119 ([M-O-CH2CHFCH=CH2] + , 100 %). HRMS (EI) 208.08958 (C12H13O2F requires
208.08963).
6.2.23 Preparation of 2-fluorobut-3-enyl 4-fluorobenzoate (93)
The novel compound was prepared following the
method outlined by Gouverneur et al. [8] A 100
cm 3 , three-necked round-bottom 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 flask was charged with 4-(trimethylsilyl)but-2-enyl 4-
fluorobenzoate (0.231 g, 0.87 mmol), anhydrous MeCN (10 cm 3 ) and Selectfluor (0.37 g,
1.0 mmol). The reaction mixture was stirred at room temperature under argon for 48 h.
After which purification by column chromatography [diethyl ether: hexane (8:92)] afforded
the product as an oil (69 mg, 37 %). δH 4.30 (1H, ddd, 3 JHF = 20.7 Hz, 2 JHH = 12.5 Hz, 3 JHH
= 7.0 Hz, Hd), 4.40 (1H, ddd, 3 JHF = 26.6 Hz, 2 JHH = 12.5 Hz, 3 JHH = 3.1 Hz, He), 5.05-5.22