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We cannot rule out another pathway that involves the tradi-
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help of a base, the reaction of intermediate D with 2a will
form product 3aa.
In summary, we have developed a method for the synthesis
of indol-3-yl aryl ketones by the Pd-catalyzed carbonylation of
indole aromatic CÀH bonds under CO-free conditions. A wide
range of functional groups was tolerated under the optimized
reaction conditions. Compared with known procedures for the
carbonylation of aromatic CÀH bonds, our new method has
the advantage that the manipulation of a harmful gas is not
required. Further tests on the scope of the reaction are under-
way.
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Experimental Section
A 10 mL oven-dried Schlenk tube was charged with aryl formates
1 (0.75 mmol), indoles 2 (0.5 mmol), PdCl2(MeCN)2 (2 mol%), Xant-
phos (5 mol%), DBU (1.5 mmol), NfF (0.75 mmol), and DMF (2 mL).
Then the tube was charged with Ar, and the reaction mixture was
stirred at 908C for ꢀ12 h. After the reaction was finished, the reac-
tion mixture was diluted in EtOAc (5 mL). The solution was filtered
through a Celite pad, which was washed with EtOAc (15–20 mL).
The organic portion was washed with a saturated solution of brine
(8 mLꢁ2), saturated NaHCO3 (10 mL), a saturated solution of brine
(8 mL), dried (Na2SO4), and concentrated in vacuum, and the result-
ing residue was purified by silica gel column chromatography
(hexane/ethyl acetate) to provide the desired products 3.
Acknowledgements
We are grateful for financial support from the Program for Inno-
vative Research Team (in Science and Technology) at University
of Yunnan Province (IRTSTYN 2014-11) and The Applied Basic Re-
search Key Project of Yunnan (2013A039).
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Keywords: carbonylation · ligand effects · palladium · reaction
mechanisms · synthesis design
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