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| Bromocyclopropane 80 (1.5 g, 2.6 mmol) was dissolved in dry THF (128 mL, 0.02 M) under Argon. Distilled dimethylpropyleneurea (DMPU, 14.3 mL) was added. Argon was then bubbled with the solution for 30 minutes. SmI2 (65 mL, 6.5 mmol, 0.1 M in THF, 2.5 equiv) was quickly added and allowed to sit for 10 minutes. The reaction was then cooled to –78°C and a 0.12 M solution of 2,4,4,6-tetrabromo-2,5-cyclohexadienone (TBCHD) in CH2Cl2 (43.3 ml, 5.2 mmol, 2 equiv) was added. For an hour the reaction was kept at -78oC over an hour. Saturated aqueous NaHCO3 (100 mL) was then added to quench the reaction. The aqueous layer was then Extracted with EtOAc (4 x 150 mL). The combined organic layers were dried over MgSO4, filtered, and concentrated in vacuo. Intermediate molecule 92 was furnished through chromatography on silica (1:3 EtOAc:hexanes) as a white foam. It was then dissolved in dry dimethylformamide (DMF, 26 mL, 0.1 M). The reagents LiBr (4.5 g, 52 mmol, 20 equiv) and Li2CO3 (3.8 mg, 52 mmol, 20 equiv) were added to the solution. At 60oC the reaction was stirred for an hour. Afterwards, it was Diluted with Et2O (400 mL), washed with saturated aqueous NaHCO3 (100 mL) and H2O (4 x 100 mL), dried with MgSO4, filtered, and then concentrated in vacuo. Dienone 76 (845 mg, 65%) was then afforded as a white solid through Chromatography on silica (1:2 EtOAc:hexanes). Molecule 76 (845 mg, 65%). IR (neat) νmax = 2953, 1678, 1426, 1253, 1128, 1081, 1038, 878, 846 cm-1. |
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a separation technique of closely related compounds that utilizes polarity by allowing a solution or mixture to seep through an adsorbent (such as silica) at different rates, thus separating the compounds.
to add more solvent without the addition of more solute to reduce concentration of a solution.
a way to separate a desired substance when it is mixed with others by bringing the mixture into contact with a solvent in which the substance of interest is soluble, but the other substances present are insoluble.
