To a 100 mL round bottom flask was added 6-(pyrrolidin-1-yl)pyridine-3,4-diamine (compound 20.2, 641 mg, 3.60 mmol, 1.0 equiv), 4-(1-(5-formyl-2,4-dimethylbenzoyl)piperidin-4-yl)benzonitrile (compound 16.4, 1.25 g, 3.60 mmol, 1.0 equiv), sodium metabisulfite (890 mg, 4.68 mmol, 1.3 equiv) and DMF (36 mL). The mixture was heated at 100° C. under air for 22 hours then allowed to cool to room temperature. Water (80 mL) was added slowly to the stirred solution until no further product precipitated. The solids were filtered and washed with water (2×15 mL) and dried to a brown solid (1.42 g). Additional product precipitated from the filtrate upon standing which was filtered and washed with water (2×10 mL) to obtain an off white solid (241 mg). The above reaction was repeated a second time in the exact manner and quantities as described to yield additional product (1.26 g of brown solid upon initial precipitation, plus 288 mg of off white solid from additional precipitation). The aqueous filtrates from the two reactions were combined and aqueous NaHCO3 was added to adjust the pH to 7. The aqueous was extracted with DCM/2% MeOH (300 mL), dried (Na2SO4), filtered and evaporated to obtain a brown solid (547 mg). All products obtained were combined and purified by silica gel chromatography (DCM/MeOH) to obtain the title compound as a yellow solid (2.37 g, 65% based on the theoretical yield for the two reactions). m/z (ES+) 505.1 (M+H)+. 1H NMR (400 MHz, DMSO-d6): δ 12.41 (br s, 1H), 8.52 (s, 1H), 7.77 (d, J=8.2 Hz, 2H), 7.66 & 7.56 (2 br singlets, amide rotamers, ArH, 1H), 7.49 (s, J=8.2 Hz, 2H), 7.29 (s, 1H), 6.31 (br s, 1H), 4.79-4.67 (m, 1H), 3.54-3.34 (m, 5H), 3.17 (app t, J=11.8, 1H), 2.99-2.82 (m, 2H), 2.63 (s, 3H), 2.33 & 2.24 (2 singlets, amide rotamers, ArCH3, 3H), 2.03-1.87 (m, 5H), 1.82-1.38 (m, 3H). Elemental analysis (C31H32N6O.1.3H2O, 528.04), found (calcd), C, 70.66 (70.51); H, 6.54 (6.60); N, 15.78 (15.92).
