Scheme 1.

Synthesis scheme and reaction conditions: (Ia) MeI (3.0 eq.), Cs₂CO₃ (1.5 eq.), DMSO, 60 °C, 24 h, 5%; (Ib) 2-fluoroethyl tosylate (4.0 eq.), Cs₂CO₃ (3.2 eq.), DMSO, 100 °C, 10 min, 61%; (IIa) MeI (3.0 eq.), MeCN, 50 °C, 30 min, 41%; (IIb) Boc₂O (1.2 eq.), THF, rt, 24 h, 85%; MeI (6.0 eq.), TBAH (5.0 eq.), MeCN, 100 °C, 10 min, 9%; conc. HCl, MeCN, rt, 24 h, 68%; (IIc) MeI (3.0 eq.), TBAH (1.2 eq.), 100 °C, 20 min, 8%; (IId) 2-fluoroethyl tosylate (4.0 eq.), Cs₂CO₃ (3.2 eq.), DMSO, 100 °C, 10 min, 75%.