Carbon tetrabromide → tert-Butyl 2-(2,2-dibromoethenyl)pyrrolidine-1-carboxylate

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Reaction Steps

To a stirred cold (minus 50° C.) solution of N-boc-prolinal (5.98 g, 30 mmol) and PPh3 (62.95 g, 240 mmol) in CH2Cl2 (200 mL) was slowly added a solution of CBr4 (39.80 g, 120 mmol) in CH2Cl2 (50 mL), and the stirring was continued for 1 hr at 0° C. To this mixture was added sat. NaHCO3 and the mixture was extracted with CHCl3. The extract was washed with H2O, dried over MgSO4, and evaporated. The residue was chromatographed on silica-gel with CHCl3 and n-hexane-AcOEt (4:1, v/v) as eluent to give 7.84 g (74%) 1-(tert-butoxycarbonyl)-2-(2,2-dibromoethenyl)pyrrolidine as colorless plates. mp 61-63; IR (KBr) 1693 cm−1; 1H-NMR (CDCl3) δ1.46 (9 H, s), 1.72-2.19 (4H, m), 3.35-3.45 (2H, m),4.35 (1H, br s), 6.36 (1H, br s); MS (FAB) m/z 352, 354, 356, 358; Anal. Calcd. for C11H17NO2Br2: C, 37.21; H 4.83; N, 3.94. Found: C, 37.14; H, 4.83; N, 4.00.

Provenance & Evidence