Reaction Steps
According to the literature procedure, a mixture of 250 mg of bis-dialdehyde 32 (0.84 mmol) and 92 mg of DMAD (dimethyl acetylenedicarboxylate) (0.84 mmol) was dissolved in 8.5 ml of anhydrous benzene and heated at 80° C. under argon. To this solution was added 119 mg of cyclohexylisocyanide (0.84 mmol) by syringe, and the heating was continued at 80° C. for further 5 days. The color of the reaction changed from red into brown. The solvent was then evaporated in vacuo, and the crude residue was purified on column chromatography using 8:2 hexane:ethylacetate to obtain first starting material, and then polarity was increased to 7:3 hexane:ethylacetate to furnish 117 mg of 50 as wine red solid in 25% yield. 1H NMR δ 10.59 (s, 1H), 9.99 (dd, 1H, J=9.9, 0.8), 8.40 (dd, 1H, J=9.9, 0.8), 7.90 (t, 1H, J=9.8), 7.71 (t, 1H, J=9.8), 7.40 (t, 1H, J=9.7), 6.72 (d, 1H, J=8.9), 3.82 (s, 3H), 3.52-3.365 (m, 1H), 3.49 (s, 3H), 1.20-2.05 (m, 10H), 0.95 (s, 9H), 0.34 (s, 3H), 0.23 (s, 3H); 13C NMR δ 189.84, 165.34, 164.39, 162.04, 157.31, 146.20, 141.70, 141.15, 139.83, 139.73, 138.19, 131.24, 130.20, 129.45, 125.96, 118.56, 86.09, 51.74, 51.35, 51.03, 34.01, 33.89, 27.34, 25.27, 24.69, 24.60, 17.95, −1.86, −3.42; LRMS (LC/MS-ESI, MeOH) m/e 550 (MH+)
