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. 2021 Jun 18;27(47):12032–12035. doi: 10.1002/chem.202101848

Scheme 2.

Scheme 2

Synthesis of building blocks 2, and 3 b,c. Reagents and conditions: a) (NH4)2SO4 (5 equiv.), H2SO4 (5 equiv.), 0 °C, 4 h, 61 %; b) 9 (5 equiv.), K2CO3 (10 equiv.), (CH3)2SO4 (10 equiv.), toluene, 60 °C, 6 h, no reaction; c) PyHBr3 (2.2 equiv.), DCM, 48 h, 83 %; d) i: H2O2 (30 %, 10 equiv.), Na2WO4 (cat.), MeOH/H2O/THF 6 : 1 : 2, 0–5 °C, 1 h; ii: K2CO3 (3 equiv.), (CH3)2SO4, (4 equiv.), 0–5 °C, 1 h, 72 % (two steps); e) CSI (1 equiv.), MeCN, 0 °C, 1 h, then DMF, 0 °C, 1 h, 95 %; f) NaH (1.2 equiv.), ClCO2Me (1.2 equiv.), DMF, 0 °C, 2 h, 94 %; g) Br2 (8 equiv.), CCl4, r. t., 12 h, 55 %, h) NaH (1.5 equiv.), MeOH, reflux; 2 h, 88 %; i) PyHBr3 (1,1 equiv.), DCM, 12 h, 77 %.