[CH:1]1[CH2:8][CH2:7][CH:6]=[CH:5][CH2:4][CH2:3][CH:2]=1.[N+](=[C:11]([C:17]([O:19][CH2:20][CH3:21])=[O:18])[C:12]([O:14][CH2:15][CH3:16])=[O:13])=[N-]>C(Cl)Cl>[C@H:1]12[C:11]([C:12]([O:14][CH2:15][CH3:16])=[O:13])([C:17]([O:19][CH2:20][CH3:21])=[O:18])[C@H:8]1[CH2:7][CH2:6][CH:5]=[CH:4][CH2:3][CH2:2]2To a solution of 1,5-cyclooctadiene (5.27 mL, 43.0 mmol) and Rh2(OAc)4 (100 mg, 0.23 mmol) in CH2Cl2 (5 mL) was added dropwise in 3 h a solution of diethyl diazomalonate (1.0 g, 5.37 mmol) in CH2Cl2 (5 mL). This solution was stirred for 24 h at rt. The CH2Cl2 was evaporated and the excess of cyclooctadiene was removed by filtration over a glass filter filled with silica (cluens: heptane). The filtrate was concentrated in vacuo and the residue was purified by column chromatography on silica gel (EtOAc:heptane, 1:10) to afford IIa.8 (1.03 g, 72%).
Wird geladen…