Diisopropylamine → 2-(3-Bromophenyl)malononitrile

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To a flame dried 5L 3-neck flask equipped with a mechamical overhead stirrer under nitrogen was added diisopropylamine (78.60 mL, 0.56 mol, 2.2 eq) and 2 L of benzene. After cooling to 0-5° C., 1.6 M n-BuLi (351.0 mL, 0.56 mol, 2.2 eq) was added dropwise via addition funnel while keeping the temperature at 0-5° C. The LDA was stirred for 45 min. at 0-5° C. 3-Bromophenylacetonitrile (50.0 g, 0.26 mol, 1.0 eq) dissolved in 200 mL of benzene was added dropwise via addition funnel keeping the temperature at 0-5° C. The mixture was stirred an additional 15 min at this temperature. 2-Chlorobenzylthiocyanate (J. Am. Chem. Soc., 1954, 76, 585) (103.0 g, 0.56 mol, 2.2 eq) dissolved in 200 mL benzene was added dropwise via addition funnel keeping the temperature at 0-5° C. During the addition, a precipitate formed. The reaction was allowed to warm to room temperature and the mixture stirred overnight. The reaction was quenched by adding water and 200 mL 10% NaOH. The layers were separated, and the benzene layer extracted with 10% NaOH (3×1 L). The basic layers were collected and acidified with conc. HCl to pH 1-2. A precipitate formed. Methylene chloride was added to dissolve the precipitate. The layers were separated and the aqueous layer reextracted with methylene chloride (2×). The methylene chloride layers were collected, dried (MgSO4) and the solvent removed in vacuo to yield 65.32 g of 2-(3-bromophenyl)malononitrile as a yellow solid. Recrystallization from methylcyclohexane yielded two crops: crop 1, 42.86 g of orange crystals, m.p. 99.5-101.5° C.; crop 2, 2.18 g of orange crystals, m.p. 97.0-99.0° C. Combined yield 79.9%. 1H-NMR (CDCl3) δ: 7.67 (s, 1H); 7.63 (d, 1H, J=7 Hz); 7.47 (d, 1H, J=7 Hz); 7.39 (t, 1H, J=7 Hz); 5.08 (s, 1H).

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