11% |
With dicyclohexyl-(2',6'-dimethoxybiphenyl-2-yl)-phosphane; palladium diacetate; potassium carbonate; caesium carbonate; In toluene; at 80℃; for 16h;Inert atmosphere; |
n-Butylboronic acid (764 mg, 7.50 mmol), K2CO3 (2.08 g, 15.0 mmol) and Cs2CO3 (490 mg, 1.50 mmol) were suspended in toluene (20.0 mL) in a Schlenk tube and subjected to four freeze-pump-thaw cycles. Under an argon atmosphere, 2-bromothiophene (480 muL, 5.00 mmol), S-Phos (21.0 mg, 0.05 mmol) and palladium acetate (56.0 mg, 0.25 mmol) were added. The initially orange, quickly darkening suspension was heated to 80 C for 16 h, cooled to room temperature and opened to the atmosphere. Water (20 mL) was added and the whole was stirred for 1 h, during which time a dark emulsion formed. The phases were separated and the aqueous layer including the dark emulsion were extracted with CH2Cl2 (3 x 25 mL).The emulsion was removed during the phase separation in the last extraction step. The combined extracts were washed with saturated aqueous NaHCO3 (50 mL). The organic layer was treated with activated charcoal, dried (Na2SO4) and the solvent was removed in vacuo. Purification by column chromatography on silica gel (petrolether -> EtOAc:petrolether 1:19) yielded 80 mg of a slightly yellow liquid (11%). 1H NMR (300 MHz, DMSO-d6): delta 0.85 (t, J = 7.0 Hz, 3H), 1.20-1.45 (m, 2H), 1.49-1.60 (m, 2H), 2.75 (m,J = 7.0 Hz, 2H), 6.75 (dd, J = 6.9/2.2 Hz, 1H), 6.90 (t, J = 6.9 Hz, 1H), 7.05 (dd, J = 6.9/2.2, 1H,) ppm;13C NMR (75 MHz, DMSO- d6): delta 13.62, 21.55, 29.77, 33.46, 123.98, 125.29, 126.80, 128.26 ppm; IR (neat): nu 3422 (b), 2923 (m), 2853 (m), 1718 (m), 1416 (w), 1267 (s), 1206 (s), 1102 (s), 1023 (s), 1004(s), 826 (s), 730 (s), 688 (s), cm-1. The NMR data were in agreement with that reported.30a, 32 |