Scheme 1.
Synthesis of 5-(5-(6-methyl-3,6-diazabicyclo[3.2.0]heptan-3-yl)pyridin-2-yl)-1H-indole and its desmethyl precursor. Reagents and conditions: (a) Pd2(dba)3, BINAP, t-BuONa in toluene, at 85 °C 20 h, 83%; (b) Pd(PPh3)4, dioxane/Na2CO3 aq. 2M)=4:1, at 115 °C 1.5 h, 77%; (c) CF3CO2H-CH2Cl2, 27%; (d) HCHO, NaBH(OAc)3, CH3CN, 31%.