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. Author manuscript; available in PMC: 2020 Jan 9.
Published in final edited form as: J Am Chem Soc. 2018 Dec 24;141(1):29–32. doi: 10.1021/jacs.8b13029

Scheme 1. Total Synthesis of Herqulines B (3) and C (14)a.

Scheme 1.

aReagents and conditions: (1) HATU (1.2 equiv), DIPEA (1.5 equiv), DMF, rt, overnight. (2) Formic acid, then sBuOH:PhMe (3:1), 105 °C (70% yield over two steps). (3) Pd(dppf)Cl2 (20 mol %), B2Pin2 (4.0 equiv), K2CO3 (6.0 equiv), DMSO:H2O (100:1, 20 mM), 90 °C, overnight (60% yield). (4) Li(0) (15 equiv), NH3, F3CCH2OH (8.0 equiv), THF, −78 °C, 1 h (77% yield). (5) [Ir(COE)2Cl]2 (20 mol %), Et2SiH2 (10 equiv), PhMe, 2 h reflux (86% yield). (6) PTSA (0.5 equiv), ethylene glycol (15 equiv), benzene, Dean–Stark trap, reflux. (7) Li(0) (15 equiv), NH3, tBuOH/THF (1:10), −78 °C, 2 h; THF/MeOH/1 N HCl (3:1); DBU, PhMe, 30 min, rt (28% over 3 steps). HATU = 1-[bis(dimethylamino)methylene]-1H-1,2,3-triazolo[4,5-b]pyridinium 3-oxide hexafluorophosphate; DIPEA = N,N-diisopropylethylamine; DMF = N,N-dimethylformamide; PhMe = toluene; dppf = 1,1’-bis(diphenylphosphino)ferrocene; DMSO = dimethyl sulfoxide; sBuOH = sec-butyl alcohol; THF = tetrahydrofuran; COE = cyclooctene; PTSA = p-toluenesulfonic acid; DBU = 1,8-diazobicyclo(5.4.0)undec-7-ene; LAH = lithium aluminum hydride; DIBAL = diisobutylaluminum hydride.