[C:1](#[N:5])[CH2:2][C:3]#[N:4].[CH2:6]1[CH2:16]CN2C(=NCCC2)[CH2:8][CH2:7]1.BrCCCCBr>CN(C=O)C>[C:2]1([C:1]#[N:5])([C:3]#[N:4])[CH2:8][CH2:7][CH2:6][CH2:16]1Malononitrile (15.0 g) was dissolved in dry DMF (200 mL) and cooled in an ice bath. Subsequently, DBU (75 mL, 2.2. equiv.) and 1,4-dibromobutane (29.6 mL, 1.1 equiv.) were added dropwise. The ice bath was removed, an extra 100 mL of dry DMF was added, and the mixture was stirred at 80° C. for 2 h. After cooling to ambient temperature, DCM was added and the mixture was washed 5 times with 5% aqueous NaHCO3. The organic phase was dried over Na2SO4 and evaporated under reduced pressure to give 40 g of a black oily substance. This was purified by flash chromatography eluting with PA:EA 9:1 (Rf=0.35, visualized with 12) to give 23.4 g of a colorless liquid. 1H NMR (400 MHz, CDCl3) δ 1.94-2.03 (m, 4H), 2.41 (t, J=7 Hz, 4H).
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