A mixture of 0.25 g of 1,3-dihydro-1-{1-[4-oxocyclohex-1-yl]piperidin-4-yl}-2H-benzimidazol-2-one, 0.25 g of 5-aminopyrimidine (H. Bredereck, F. Effenberger and E. H. Schweizer, Chem. Ber. 1962 95, 803-9), 2 mL of 1,2-dichloroethane, 0.5 mL of acetic acid and 0.35 g of sodium triacetoxyborohydride was stirred at room temperature for 48 h. The reaction mixture was poured into 200 mL chloroform and 20 mL saturated aqueous Na2CO3 and the layers separated. The aqueous layer was extracted with 2×25 mL of CHCl3 and the combined organic layers dried over MgSO4 and concentrated under reduced pressure. Preparative TLC on silica gel, eluting with 85:15:5 Et2O:MeOH:conc. NH4OH gave 85 mg of trans-1,3-dihydro-1-{1-[1-(5-pyrimidinylamino)cyclohex-4-yl]piperidin-4-yl}-2H-benzimidazol-2-one: 1H NMR (400 MHz, CDCl3 +5% CD3OD) 8.44 (s, 1H), 8.12 (m, 2H), 7.36 (m, 1H), 7.09 (m, 3H), 4.3 (br m, 1H), 3.65 (br m, 2H), 3.2 (br m, 2H), 2.45 (m, 5H), 2.0 (m, 2H), 1.85 (br m, 4H), 1.65 (m, 4H): Analysis calculated for C22H28N6 O.1.05 H2O.0.25 CHCl3 : C: 60.56, H: 7.17, N: 18.68; found C: 60.81, H: 7.17, N: 18.68, and 75 mg of cis-1,3-dihydro-1-{1-[1-(5-pyrimidinylamino)cyclohex-4-yl]piperidin-4-yl}-2H-benzimidazol-2-one: 1H NMR (400 MHz, CDCl3 +5% CD3OD) 8.43 (s, 1H), 8.08 (m, 2H), 7.65 (m, 1H), 7.1 (m, 3H), 4.6 (br m, 1H), 3.6 (br m, 2H), 3.25 (br m, 2H), 3.0 (br m, 5H), 2.3 (m, 4H), 2.0 (m, 2H), 1.75 (br m, 2H), 1.35 (m, 2H): Analysis calculated for C22H28 N6O.0.25 H2O.0.75 CHCl3 : C: 55.90, H: 5.97, N: 17.16; found C: 56.19, H: 5.96, N: 17.14.
