[Cl:1][C:2]1[C:10]2[O:9][CH2:8][O:7][C:6]=2[CH:5]=[CH:4][C:3]=1[NH2:11].Cl.[O:13]1CCOC[CH2:14]1.C(Cl)(Cl)=O>C1COCC1>[Cl:1][C:2]1[C:10]2[O:9][CH2:8][O:7][C:6]=2[CH:5]=[CH:4][C:3]=1[N:11]=[C:14]=[O:13]To a vial containing 4-chlorobenzo[d][1,3]dioxol-5-amine (28.8 mg, 0.168 mmol, 1 equiv.) in 1 mL THF was added 4M HCl in 1,4-dioxane (0.042 mL, 1 equiv.) followed by phosgene (20% in toluene; 0.360 mL, 0.684 mmol, 4 equiv.). The vial was capped and heated to 70° C. for 1 h, the solvent was removed under, the residue redissolved in toluene and solvent was again removed under vacuum to eliminate any remaining phosgene yielding 4-chloro-5-isocyanatobenzo[d][1,3]dioxole used as such in the next step.
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