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A.; Cella, R.; Vieira, A. S. Tetrahedron 2007, 63, 3623; (e) Darses, S.; Genêt, J. P.
Chem. Rev. 2008, 108, 288.
21.16. 11B NMR (DMSO-d6, 96 MHz): d 3.61; 19F NMR (DMSO-d6, 282 MHz): d
À137.7.
8. (a) Cella, R.; Venturoso, R. C.; Stefani, H. A. Tetrahedron Lett. 2008, 49, 16; (b)
Bellomo, A.; Gonzalez, D.; Stefani, H. A. J. Organomet. Chem. 2008, 693, 1136; (c)
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10. General procedure for potassium alkenyltrifluoroborate synthesis: In a dried two-
necked 50-mL flask with a nitrogen atmosphere was added dropwise 4-methyl
phenylacetylene (20 mmol, 2.65 mL) at 0 °C. Catecholborane (20 mmol,
2.15 mL) was then added dropwise at the same temperature. The ice bath
was removed, and the resulting mixture was heated and stirred for 4 h at 75 °C,
after which it was allowed to cool to room temperature. Next, a saturated
aqueous solution of potassium hydrogen difluoride (80 mmol, 6.24 g) was
added to the vigorously stirred solution. After 5 h, a white precipitate was
formed, the solvent was removed under reduced pressure, and the resulting
white solid was washed with acetone (100 mL) and with hot acetone. The
resulting organic solution was filtered, and the solvent was removed to afford a
fluffy white solid. This solid was then dissolved in hot acetone and precipitated
with cold diethyl ether (40 mL), after which the solution was cooled to À20 °C
to complete the precipitation of the solid. The product was collected as a white
crystalline solid (62%). 1H NMR: (DMSO-d6, 300 MHz): d 7.18 (d, J = 7.6 Hz, 2H);
7.03 (d, J = 7.6 Hz, 2H); 6.42 (d, J = 18.2 Hz, 1H); 6.09 (d, J = 18.2 Hz, 1H); 2.23
(s, 3H). 13C NMR (DMSO-d6, 75 MHz): d 138.05, 135.21, 133.37, 129.30, 125.75,
11. General procedure for all homocoupling reactions (Table 2, entry 2): A 50-mL
flask under
a nitrogen atmosphere was charged with potassium methyl
styryltrifluoroborate (0.5 mmol, 0.112 g), Pd(OAc)2 (15 mol %, 16.50 mg), Ag2O
(3 equiv, 34.76 mg), and DMSO (3 mL). The reaction mixture was heated at
70 °C for 7 h and the reaction was followed by TLC. After completion, the
reaction mixture was allowed to reach rt and then NH4Cl (30 mL) was added,
and the organic phase was extracted with ethyl acetate (3 Â 30 mL). The
organic layers were combined, dried (MgSO4), and the solvent was removed
under vacuum to provide a viscous yellow oil. The oil was purified by column
chromatography using a mixture of hexane/ethyl acetate (96:4) as the eluent
to afford the solid products (see Table 2). Yield 65%. White solid. 1H NMR:
(CDCl3, 300 MHz): d 7.38 (d, J = 7.95 Hz, 4H); 7.18 (d, J = 7.86 Hz, 4H); 6.95 (dd,
J = 12.0, 2.65 Hz, 2H); 6.66 (dd, J = 12.0, 2.91, 2H); 2.39 (s, 6H). 13C NMR (CDCl3,
75 MHz): d 137.36, 134.72, 132.26, 129.38, 128.51, 126.25, 21.26. MS 234 (82);
219 (100); 204 (49); 115 (24); 105 (47); 77 (21).
12. General procedure for all cross-coupling reactions: A two-necked 50-mL flask
under a nitrogen atmosphere was charged with potassium 4-methyl styryl-
trifluoroborate (0.5 mmol, 0.112 g), potassium 4-bromo styryltrifluoroborate
(0.5 mmol; 14.4 mg), Pd(OAc)2 (15 mol %, 16.50 mg), Ag2O (3 equiv, 34.76 mg),
and DMSO (3 mL). The reaction mixture was heated at 70 °C for 7 h, and the
reaction was followed by TLC. After completion, the reaction mixture was
allowedtoreachrtand thenNH4Cl(30 mL)wasadded, andtheorganicphase was
extracted with ethyl acetate (3 Â 30 mL). The organic layers were combined,
dried (MgSO4), and the solvent was removed under vacuum to provide a viscous
yellow oil. The oil was purified by column chromatography using a mixture of
hexane/ethylacetate (96:4)as the eluentto afford the solid products(see Table 3,
entry 4: 38%—MS = 206 (100), 191 (40), 128 (36), 91 (71), 77 (17); 32%—MS = 284
(56), 205 (100), 190 (25), 128 (27), 101 (37), 89 (33); 30%—MS = 204 (100), 101
(27), 89 (17), 76 (14).