To 122 mg (0.299 mmol based on 74% purity) of 1-(3-cyclohex-1-enyl-4-nitro-phenyl)-4-methyl-piperazine (as prepared in the previous step) in 5.0 mL of EtOH-water (2:1) was added 83.8 mg (1.50 mmol) of iron powder and 160 mg (2.99 mmol) of NH4Cl and the mixture refluxed under Ar for 12 h. An additional 83.8 mg (1.50 mmol) of iron powder was added, and the mixture was refluxed for 1 h. The mixture was poured into EtOAc (12 mL), filtered (Celite), washed with EtOAc (2×4 mL), concentrated in vacuo and dissolved in anh THF (4.0 mL). The resulting aniline solution was placed under Ar and used immediately in the following reaction. 61.6 mg (0.449 mmol) of 5-cyanofuran-2-carboxylic acid (as prepared in Example 1) in 2.5 mL of anh dichloromethane under a CaSO4 drying tube was treated with 60.0 μL (0.688 mmol) of oxalyl chloride followed by 10 μL of anh DMF. The solution was stirred for 25 min and quickly concentrated in vacuo at 20-25° C. The residue was placed under high vacuum for 2-3 min and then immediately placed under Ar, cooled to 0° C. in an ice bath and treated with the aniline solution produced above followed by 104 μL (0.598 mmol) of DIEA. After stirring 30 min at RT, the mixture was concentrated in vacuo, dissolved in EtOAc (20 mL), washed with 1M K2CO3 (2×10 mL) and brine (10 mL), dried (Na2SO4) and concentrated in vacuo. The resulting residue was chromatographed on a 10-g silica SPE column with 1-4% MeOH-dichloromethane to give a yellow resin which was then crystallized from Et2O-hexane to afford 84.7 mg (72%) of the title compound as a crystalline yellow solid. 1H-NMR (CDCl3; 400 MHz): δ 8.57 (br s, 1H), 8.26 (d, 1H, J=9.0 Hz), 7.20, 7.23 (AB q, 2H, J=3.7 Hz), 6.86 (dd, 1H, J=9.0, 2.9 Hz), 6.74 (d, 1H, J=2.9 Hz), 5.84-5.85 (m, 1H), 3.20-3.22 (m, 4H), 2.57-2.59 (m, 4H), 2.36 (s, 3H), 2.23-2.30 (m, 4H) and 1.79-1.84 (m, 4H). Mass spectrum (ESI, m/z): Calcd. for C23H26N4O2, 391.2 (M+H), found 391.2.
