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. Author manuscript; available in PMC: 2021 Sep 17.
Published in final edited form as: Tetrahedron Lett. 2020 Aug 16;61(38):152353. doi: 10.1016/j.tetlet.2020.152353

Scheme 3:

Scheme 3:

Revised route to the furo[2,3-b]pyridine 19. i) H2SO4, Mg2SO4, tBuOH, CH2Cl2, rt, 16 h, 92%. ii) 1.1 eq. 17, 3.5 eq.NaH, THF, 0–50 °C, 3 h, 86%. iii) TFA, CH2Cl2, rt, 16 h. 89%. iv) Tf2O, DIPEA, CH2Cl2, −10–25 °C, 3 h, 71%.