Scheme 3. Total synthesis of (–)-psychotriasine (2). Reagents and conditions: (a) (i) NaHMDS, Boc2O, THF, –60 °C; (ii) RANEY® nickel, hydrazine hydrate, MeOH, sealed tube, 70 °C, 88% yield over 2 steps; (b). Pd(OAc)2 (0.2 equiv.), xantphos (0.3 equiv.), t-BuONa (2.0 equiv.), toluene, 80 °C, 71% yield; (c) 13, Pd(OAc)2 (0.2 equiv.), DtBPF (0.3 equiv.), K2CO3 (2.5 equiv.), NMP, 110 °C, 83% yield; (d) (i) DIBAL-H (3.0 equiv.), toluene, –78 °C; (ii). ClCO2Me (3.0 equiv.), Na2CO3 (3.0 equiv.), DCM–H2O (2 : 1 ratio), rt, 64% yield over 2 steps; (e) (i) CF3CO2H, DCM, 0 °C; (ii) Red-Al (12.0 equiv.), toluene, reflux, 51% yield over 2 steps. Alkyne 13: N-(methoxycarbonyl)-4-(trimethylsilyl)-3-butynylamine.
