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Page 4 of 17 Wu et al. Chem Synth 2023;3:6 https://dx.doi.org/10.20517/cs.2022.42

Table 1. Screening of catalysts and optimization of reaction conditions a

Entry Cat. Solvent T ( C) 1a: 2a Yield (%) b
o
1 4a CHCl 3 20 1:1.2 55
2 4b CHCl 3 20 1:1.2 trace
3 4c CHCl 3 20 1:1.2 45
4 4d CHCl 3 20 1:1.2 11
5 4e CHCl 3 20 1:1.2 trace
6 4f CHCl 3 20 1:1.2 trace
7 4g CHCl 3 20 1:1.2 trace
8 4a toluene 20 1:1.2 43
9 4a acetone 20 1:1.2 trace
10 4a MeCN 20 1:1.2 trace
11 4a THF 20 1:1.2 trace
12 4a EtOAc 20 1:1.2 trace
13 4a CHCl 3 20 1:1.5 64
14 4a CHCl 3 20 1.2:1 62
15 4a CHCl 3 20 1.5:1 70
16 c 4a CHCl 3 20 1.5:1 76
d
17 4a CHCl 3 20 1.5:1 61
e
18 4a CHCl 3 20 1.5:1 37
19 c 4a CHCl 3 30 1.5:1 85
c
20 4a CHCl 3 40 1.5:1 79
a
Unless otherwise indicated, the reaction was carried out at a 0.1 mmol scale and catalyzed by 10 mol% Cat. in a solvent (1.0 mL) at the indicated
b c d e
temperature for 12 h; Isolated yield; Performed in 0.5 mL of CHCl ; Performed in 2.0 mL of CHCl ; Performed in 3.0 mL of CHCl .
3
3
3
occur in chloroform (entry 1) and toluene (entry 8), with chloroform acting as a better reaction medium in
terms of yield. To further improve the yield of this model reaction, other reaction parameters, such as
reagent ratio and reaction concentration and temperature, were modulated (entries 13-20). It was found