background and overview[1]
o-trifluoromethylstyrene is a commonly used monomer in the synthesis of polymer materials fluorinated polystyrene. so far, there are two methods for the synthesis of o-trifluoromethylstyrene reported in the literature. the first method is to use trifluoromethylphenylethyl alcohol as the raw material and potassium hydrogen sulfate as the dehydrating agent to perform a heating dehydration reaction. the second method is to use trifluoromethylphenylethyl alcohol as the raw material, use phosphorus pentoxide as the dehydrating agent in anhydrous benzene solvent to perform a heating dehydration reaction. since o-trifluoromethylstyrene is unstable, current reporting methods are all in acidic conditions. when heated and dehydrated, self-polymerization of o-trifluoromethylstyrene will occur, resulting in a decrease in yield. therefore, the synthesis of this compound has not yet yielded satisfactory results so far.
preparation[1-2]
report 1,
add potassium dihydrogen phosphate (19g) and 3-trifluoromethylphenylethyl alcohol (190g) into the reaction bottle. then heat to 100°c and stir for 12 hours. after distillation under reduced pressure, o-trifluoromethylstyrene (65-66°c/41mmhg) was obtained as a colorless liquid with a yield of 90% and a purity of 99.0% (gc).
report 2,
add kosime3 (896 mg, 7 mmol, 3.5 equivalents) and tripalladium dibenzylideneacetone (58 mg, 0.1 mmol, 0.05 equivalents) into a 10 ml round-bottomed flask equipped with a magnetic stirring bar. and triphenylphosphine oxide (28 mg, 0.1 mmol, 0.05 equivalent), filled with argon, and then filled the flask with thf (4 ml), 2-bromotrifluorotoluene (450 mg, 2 mmol) and dvds (500 μl, 2.2) via a syringe. mmol, 1.1 equivalent). the mixture was placed in a preheated oil bath and heated to reflux for 3 hours. after the completion of the reaction was confirmed by gc analysis, the mixture was cooled to room temperature, then filtered through a small silica gel pad (5g), rinsed the silica plug with 50ml ether, and the organic layer was concentrated in vacuo and passed through column chromatography (silica gel, 30mmx140mm, pentane alkane; then rpc-18 silica gel, methanol/water 9:1) purified the crude product to obtain 172 mg (52%) o-trifluoromethylstyrene as a clear colorless oil, yield 172 mg (52%). 1hnmr: (500mhz, cdcl3) 7.66 (d, j=7.8, 1h, hc (7)), 7.63 (d, j=7.8, 1h, hc (4)), 7.52 (t, j=7.6, 1h, (hc (6))), 7.36 (t, j=7.7, 1h, hc (5)), 7.10 (ddd, j=17.3, 11.0 and 2.5, 1h, hc (2)), 5.75 (d, j=17.1, 1h, htransc (1)), 5.42 (dd, j=11.0 and 1.2, 1h, hcisc (1). 13cnmr : (125mhz, cdcl3) 137.0 (c (3)), 133.3 (c (4)), 132.1 (c (2)), 127.7 (c (5)), 127.3 (c ( 6)), 125.8 (q, c (9)), 125.6 (c (8)), 123.4 (c (7)), 118.2 (c (1)). ir: 3083 (w), 2886 ( m), 2801 (m), 1876 (w), 1611 (s), 1555 (w), 1522 (s), 1480 (m), 1444 (m), 1407 (w), 1351 (s), 1228 ( m), 1187 (s), 1166 (s), 1129 (w), 1061 (m), 990 (m), 946 (m), 887 (m), 821 (s), 751 (m), 691 ( w).
references
[1]cn101781161-a preparation method of o-trifluoromethylstyrene compounds
[2] denmark s e , butler c r . vinylation of aromatic halides using inexpensive organosilicon reagents. illustration of design of experiment protocols[j]. journal of the american chemical society, 2008, 130(11):p.3690-3704 .
