Skip to main content
. Author manuscript; available in PMC: 2022 Aug 20.
Published in final edited form as: J Org Chem. 2021 Jul 21;86(16):11237–11262. doi: 10.1021/acs.joc.1c00920

Table 3.

Optimization of Anthraquinone Triflation

graphic file with name nihms-1757754-t0034.jpg
entry solvent base (equiv) triflating reagent temp (°C) time (h) 109 (% yield)
1 CH2Cl2 Pyr (20) PhNTf2 0–40 15 0
2 CH2Cl2 DBU (10) PhNTf2 0–40 15 0
3 THF LDA (3) PhNTf2 −78–23 15 0
4 CH2Cl2 DBU (20) Comins’ 0–23 15 0
5 CH2Cl2 Pyr (20) Comins’ 0–23 15 0
6 CH2Cl2 Pyr (3) Tf2O −78–0 2 36
7 THF NaH (10) Tf2O −78 2 0a
8 CH2Cl2 NaH (10) Tf2O 0 5 50
9 DME NaH (10) Tf2O 0 5 50b
10 CH2Cl2 NaH (5) Tf2O 0 5 0
11 CH2Cl2 NaH (20) Tf2O 0 5 72%
12 CH2Cl2 NaH (20) + Pyr (3) Tf2O 0 5 73%c
a

The polymer of tetrahydrofuran (THF) produced by triflic anhydride (Tf2O) decomposes the mixture of product and starting material quickly during purification.

b

Mixture of isomers.

c

The deprotonation of anthraquinone 3 with sodium hydride is very slow on larger scales (>0.1 mmol). The addition of pyridine after Tf2O increased the conversion and reaction rate at a 0.23 mmol scale.