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. 2020 Nov 10;12(2):803–811. doi: 10.1039/d0sc05763k

Optimization of reaction conditions.

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Entry Variation from the assigned conditions Yieldb (%)
3a 4 5 6
1a None 50 4aI/n.d n.d n.d
2 DMF + TFA(10.0 equiv.) n.d 4aI/n.d n.d 14
3 THF + TFA(10.0 equiv.) n.d 4aI/n.d n.d 33
4 HFIP + TFA(10.0 equiv.) 5 4aI/n.d n.d 6
5 Toluene + TFA(10.0 equiv.) 5 4aI/n.d n.d 35
6 Dioxane + TFA(10.0 equiv.) n.d 4aI/n.d n.d 46
7 AcOH + TFA(10.0 equiv.) n.d 4aI/n.d n.d 20
8 Air instead of O2 43 4aI/n.d n.d n.d
9 N2 instead of O2 13 4aI/n.d n.d n.d
10 80 °C instead of 100 °C 33 4aI/n.d n.d n.d
11 120 °C instead of 100 °C 26 4aI/n.d n.d n.d
12 2b instead of 2a 65 4aI/n.d n.d n.d
13 2c instead of 2a n.d 4a/37 n.d n.d
14 2d instead of 2a 4 4a/76 n.d n.d
15 2e instead of 2a n.d 4aII/n.d 18 n.d
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a

Assigned conditions: 1a (0.20 mmol), 2a (0.30 mmol), TFA (1.6 mL), 100 °C, 15 h, and O2 atmosphere.

b

Isolated yields (n.d: not detected).