Reagents and conditions: (a) tetrahydro-2H-pyran-4-amine, 3-aminothietane 1,1-dioxide hydrochloride, or 1,1-dioxothian-4-amine, Hünig’s base, EtOH, 90 °C, 18 h, 30–61%; (b) Pd/C, H2, MeOH, rt, 40 min to 3 h, 100%; (c) CDI, MeCN, 3–12 h, 21–77%; (d) Cs2CO3, MeCN, 70 °C, 18 h, 33–43% or Cs2CO3, KI, DMF, 80 °C, 8 h, 31%; (e) TBAF, THF, rt, 32 h, 65%.