Scheme 2.
Synthesis of DAPN-PD. Reagents and conditions: (a) DBU, TMSOTf, CH3CN, 65 °C, 3 h, 79.5%; (b) NH3/MeOH, rt, 12 h, 69.9%; (c) 4, THF, t-BuMgCl, 0 °C to rt, 6 h, 80%; (d) NaN3, (Bu)4NI, DMF, 80 °C, 18 h; (e) H2, 20% Pd(OH)2, i-PrOH, rt, 52% (two steps).