[N+]([CH2:3][C:4]([O:6][CH2:7][CH3:8])=[O:5])#[C-].[C:9]([O-])([O-])=O.[K+].[K+].BrC[C:17]1[CH:22]=[C:21]([Cl:23])[C:20]([Cl:24])=[CH:19][C:18]=1[CH2:25]Br.[C:27](#[N:29])C>CCCC[N+](CCCC)(CCCC)CCCC.OS([O-])(=O)=O>[CH2:7]([O:6][C:4]([CH:3]1[CH2:9][C:19]2[C:18](=[CH:17][CH:22]=[C:21]([Cl:23])[C:20]=2[Cl:24])[CH:25]1[N+:29]#[C-:27])=[O:5])[CH3:8]To a solution of ethyl isocyanoacetate (3.85 mL, 35 mmol) in anhydrous ACN (300 mL) is added finely ground anhydrous K2CO3 (29 g, 210 mmol), TBAHS (tetrabutyl ammonium hydrogen sulfate, 2.34 g, 7 mmol), and 1,2-bis-(bromomethyl)-4,5-dichlorobenzene (11.6 g, 35 mmol). The resulting heterogeneous mixture is stirred at 80° C. overnight. The reaction mixture is cooled down to RT and filtered to remove the unwanted salts. The filtrate is concentrated in vacuo. The residue is purified by flash column chromatography (200 g silica gel; gradient elution: 0-25% EtOAc in heptane) to give a pure product as white powder (6.63 g, 66%).
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