Organic Letters
Letter
The CsCl byproduct can be easily separated from the reaction
system and can be used for other purposes resulting in reduced
costs for our esterification methodology.
We tried to study the mechanism of the esterification of acyl
chloride and halohydrocarbon. Having established that O
comes from Cs2CO3, not air (Table 1, entry 7), we studied the
type of gases produced by this esterification reaction, and CO is
the main ingredient (Figure 1). When TEMPO was added to
using Cs2CO3 as the oxygen source. Twenty-four substrates
were tested, and good yields were obtained. The controlled
experiments demonstrated that the O in the ester products
comes from Cs2CO3 and this esterification may proceed
through a free radical pathway. Further studies will be aimed at
further investigations into the reaction mechanism.
ASSOCIATED CONTENT
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S
* Supporting Information
The Supporting Information is available free of charge on the
Experimental procedure, control experiments, experi-
ment on a gram scale, compound characterization data,
AUTHOR INFORMATION
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Corresponding Author
Notes
Figure 1. Gas mass spectra of the esterification reaction using acyl
chloride and alohydrocarbon.
The authors declare no competing financial interest.
the reaction system, no product 2a was obtained. So the
esterification of an acyl chloride and a halohydrocarbon may
proceed through a free radical. To further confirm this result,
we utilized electron paramagnetic resonance (EPR) spectros-
copy and obtained an EPR spectrum which displayed a
resonance characteristic of an oxygen radical (Figure 2).
ACKNOWLEDGMENTS
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We gratefully acknowledge financial support from the National
Natural Science Foundation of China (21403219), National
Engineering Laboratory for Methanol to Olefins.
REFERENCES
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On the basis of the above-mentioned results and pertinent
literature, we proposed a possible reaction pathway (Scheme
4). First, benzoyl chloride reacted with Cs2CO3 forming
intermediate A which was unstable and decomposed forming
free radical B and CO gas. Finally, the free radical B reacted
with 1,2-dichloroethane forming product 2a.
In summary, we report the first effective method for the
construction of esters from acyl chloride and halohydrocarbon
Scheme 4. Possible Reaction Pathway
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