Scheme 3. Analogs prepared via hydroboration-oxidation of enol triflate 2a.
aReagents and conditions: (a) BH3·THF, THF, 0 °C, 3 h, then H2O followed by NaBO3•H2O, 18 h, 0 °C to rt, 18 h, 31% (and 39% of recovered starting material); (b) diethyl(3-pyridyl)borane, Pd(PPh3)2Cl2, NaHCO3, THF, H2O, 60 °C, 20 h, 49%; (c) K2CO3, MeOH, rt, 15 h, 92%; (d) Dess–Martin periodinane, CH2Cl2, 0 °C to rt, 16 h, 89%; (e) diethyl(3-pyridyl)borane, Pd(PPh3)2Cl2, NaHCO3, THF, H2O, 60 °C, 17 h, 82%; (f) K2CO3, MeOH, rt, 17 h, 88%; (g) NH2OH•HCl, NaOAc, EtOH, H2O, rt, 17 h, 83%; (h) NH2OH•HCl, NaOAc, EtOH, H2O, rt, 24 h, 98%; (i) SOCl2, THF, 0 °C, 4 h, then H2O, 47%; (j) K2CO3, MeOH, rt, 17 h, 100%.
