Br[C:2]1[N:3]([CH2:9][O:10][CH2:11][CH2:12][Si:13]([CH3:16])([CH3:15])[CH3:14])[CH:4]=[C:5]([C:7]#[N:8])[N:6]=1.C([Mg]Cl)(C)C.C([C:24]([O:26][CH2:27][CH3:28])=[O:25])#N>C1COCC1>[CH2:27]([O:26][C:24]([C:2]1[N:3]([CH2:9][O:10][CH2:11][CH2:12][Si:13]([CH3:16])([CH3:15])[CH3:14])[CH:4]=[C:5]([C:7]#[N:8])[N:6]=1)=[O:25])[CH3:28]To a solution of 2-bromo-1-(2-trimethylsilanyl-ethoxymethyl)-1H-imidazole-4-carbonitrile (0.55 g, 1.8 mmol) (as prepared in the previous step) in THF (6 mL) at −40° C. was added dropwise a solution of 2M i-PrMgCl in THF (1 mL). The reaction was allowed to stir for 10 min at −40° C. and then cooled to −78° C., and ethyl cyanoformate (0.3 g, 3.0 mmol) was added. The reaction allowed to attain RT and stirred for 1 h. The reaction was quenched with satd aq NH4Cl, diluted with EtOAc (20 mL) and washed with brine (2×20 mL), and the organic layer was dried over Na2SO4 and then concentrated. The title compound was eluted from a 20-g SPE cartridge (silica) with 30% EtOAc/hexane to give 0.40 g (74%) of a colorless oil. Mass spectrum (ESI, m/z): Calcd. for C13H21N3O3Si, 296.1 (M+H), found 296.1.
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