Scheme 4a.
aReagents and conditions: (a) mono-propagylamine hydrochloride, N(i-Pr)2Et, CH2Cl2, rt to 50 °C, 1 h, 98%; (b) Aryl bromide, 10 mol% Pd(PPh3)4, NEt3, 5 mol% CuI, DMF, 80 °C (microwave), 1 h, 73%; (c) H2, Pd/C, MeOH, 12 h, 63%; (d) TFA, CH2Cl2, rt, 30 min., 46%; (e) 10% KOH(aq), MeOH, 60 °C, 12 h, then TFA, CH2Cl2, rt, 30 min., 22% (over 4 steps).