[CH3:1][C:2]1([CH3:16])[O:6][C@@H:5]([CH2:7][CH2:8]OS(C)(=O)=O)[C:4]([CH3:15])([CH3:14])[O:3]1.[N-:17]=[N+:18]=[N-:19].[Na+]>CN(C)C=O>[N:17]([CH2:8][CH2:7][C@@H:5]1[O:6][C:2]([CH3:16])([CH3:1])[O:3][C:4]1([CH3:15])[CH3:14])=[N+:18]=[N-:19]Step H To a solution of methanesulfonic acid 2-((S)-2,2,5,5-tetramethyl-[1,3]dioxolan-4-yl)-ethyl ester (2.5 g, 9.9 mmol) in N,N-dimethylformamide (50 mL) was added NaN3 (6 g, 70 mmol). The reaction mixture was heated at 95° C. for 4 h. Then the mixture was partitioned between ethyl acetate and water. The organic layer was separated, washed with water, brine several times, dried over MgSO4, concentrated to give (S)-5-(2-azido-ethyl)-2,2,4,4-tetramethyl-[1,3]dioxolane as a yellow oil (1.6 g, 80%).
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