Reagents and conditions: (a) (1)
TBSOTf, 2,6-lutidine, DCM, rt, 1 h. (2) HF-pyr, THF, rt, 0.5 h. (b)
Cyclohexyl isocyanate, TEA, DCM, rt, 0.5 h, 86% (2 steps). (c) 1-Ethynyl-4-fluorobenzene,
TEA, XPhos-Pd-G3, MeCN, 70 °C, 14 h, 94%. (d) DDQ, DCM, pH 7
buffer, rt, 5 h, 66%. (e) PPh3, DIAD, phthalimide, THF,
0–23 °C, 18 h. (f) Methylhydrazine, EtOH, 80 °C,
1 h, 36% (2 steps). (g) CH2O, Na(OAc)3BH, DCM,
rt, 6 h, 51%.