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

VI
Appendix
stirred at room temperature for 15 minutes. After which, 2-chlorobut-3-enyl benzoate (67 mg,
0.32 mmol), sodium fluoride (40 mg, 0.96 mmol) and 15-crown-5 (0.19 cm 3 , 0.96 mmol)
were added and the reaction mixture left to stir. After stirring overnight, the reaction was
quenched with water (10 cm 3 ) and the aqueous phase extracted with diethyl ether (3 x 10
cm 3 ). The combined organic phases were dried over MgSO4, concentrated in vacuo. Analysis
by 1 H and 19 F NMR spectroscopy of the crude product revealed that no fluorinated product
had formed.
A 50 cm 3 , two-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. Pd(dba)2 (l equiv.), PPh3 (2 equiv.) and anhydrous
CDCl3 were added to the reaction flask in a dry box. Subsequently, the flask was reattached
to the Schlenk line, filled with nitrogen and charged with allyl halide (2 equiv.), after stirring
the reaction for 2 hours, fluoride (5 equivalents) was added to the reaction flask, a small
aliquot was transferred to an NMR tube, and the reaction was monitored by 1 H and 19 F NMR
spectroscopy. However, no desired product was formed when fluoride = TBAF, TASF,
TREAT HF or HF.pyridine.
A4 Attempted reactions in Chapter 5
Attempted preparation of 2,2-difluorobut-3-enyl 4-methylbenzoate
The title compound was prepared using a method
outlined by Nakamura et al. [3] A 100 mL, 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 mL DCM, 0.49 mmol) and
pyridine (1 mL) and cooled to 0 ºC. 4-(trifluoromethyl)benzoyl chloride (0.6 mL, 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 mL) and the organic layer separated and washed with HCl (10 mL, 5
% aqueous solution), saturated brine (10 mL), saturated NaHCO3 (10 mL) and saturated brine
(10 mL) successively, then dried over magnesium sulphate. Purification by flash column
chromatography [chloroform: hexane (50:50)] and concentration in vacuo failed to afford the
desired product.
Attempted preparation of 3,3-difluoro-2-phenylpent-4-en-2-ol
The title compound was prepared using a method outlined by
Audouard et al. [4] A 25 mL round-bottomed flask was set up in a
sonicating bath, 3-bromo-3,3-difluoroprop-1-ene (0.3 cm 3 , 2.95
mmol),acetophenone (0.17 cm 3 , 1.48 mmol), indium powder (0.31 g,
2.95 mmol) and water (14 mL) were added successively, and the
reaction mixture sonicated for 24 h at room temperature. After 24 h
the reaction mixture was quenched with HCl (10 mL of a 1M aqueous solution), extracted
with dichloromethane and the combined organic layers washed with brine (20 mL) and dried
over magnesium sulphate. Purification by flash column chromatography [petroleum ether:
diethyl ether (85:15)] and concentration in vacuo failed to afford the desired product.