反应详情

A dry vial was charged with freshly activated Mg turnings (115 mg, 5 mmol), 100 μL of anhydrous THF and a drop of 1,2-dibromoethane under Ar. This mixture was treated dropwise with a solution of 6-bromohexylbenzene (240 mg, 1 mmol) in THF (1 mL) at 23° C. The mixture was warmed and sonicated repeatedly until Grignard formation occurred. The gray solution of the Grignard reagent was added to a solution of methyl 5-(pyridin-2-yl)-1,3,4-oxadiazole-2-carboxylate (S7, 40 mg, 0.17 mmol) in THF (2 mL) at −40° C. Stirring was continued for 2 h before the reaction was quenched by the addition of MeOH at −40° C. The mixture was extracted with EtOAc and washed with water, saturated NaHCO3 and saturated aqueous NaCl followed by separation and evaporation. Flash chromatography (SiO2, 1×4 cm, 40% EtOAc-hexanes) afforded the title compound (30 mg, 51%) as a white solid: 1H NMR (CDCl3, 400 MHz) δ 8.85 (d, 1H, J=4.7 Hz), 8.30 (d, 1H, J=7.9 Hz), 7.93 (td, 1H, J=1.5, 7.8 Hz), 7.54 (ddd, 1H, J=0.9 4.7, 7.6 Hz), 7.26-7.30 (m, 2H), 7.16-7.19 (m, 3H), 3.31 (t, 2H, J=7.3 Hz), 2.62 (t, 2H, J=7.6 Hz), 1.82 (quintet, 2H, J=7.3 Hz), 1.66 (quintet, 2H, J=7.5 Hz), 1.43 (m, 4H); 13C NMR (CDCl3, 100 MHz) δ 187.1, 165.0, 161.2, 150.8, 142.6 (2C), 137.3, 128.3, 128.2, 126.7, 125.6, 124.0, 40.0, 35.8, 31.2, 28.9, 28.8, 23.5; IR (film) νmax 2927, 2856, 1709, 1589, 1442, 1398, 1038, 986, 798, 754, 710 cm−1; HRMS-ESI-TOF m/z 336.1717 ([M+H]+, C20H21N3O2 requires 336.1706).

1. temperatureThe mixture was warmed
2. customsonicated repeatedly until Grignard formation
3. customwas quenched by the addition of MeOH at −40° C
4. extractionThe mixture was extracted with EtOAc
5. washwashed with water, saturated NaHCO3 and saturated aqueous NaCl
6. customfollowed by separation and evaporation