Palladium‐Catalyzed Pyridine‐Directed Regioselective Oxidative C–H Acylation of Carbazoles by Using Aldehydes as the Acyl Source

We herein report a highly regioselective reaction for the palladium‐catalyzed oxidative acylation of carbazole derivatives with various aromatic and aliphatic aldehydes as the acyl source. The carbazole derivatives are N‐protected with an easily removable pyridine moiety, which directs the Pd‐cataly...

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Bibliographic Details
Published in:European journal of organic chemistry 2017-01, Vol.2017 (2), p.332-340
Main Authors: Maiti, Subhadip, Burgula, Laxminarayana, Chakraborti, Gargi, Dash, Jyotirmayee
Format: Article
Language:English
Subjects:
Acylation
Aldehydes
C‐H activation
Nitrogen heterocycles
Palladium
Regioselectivity
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Summary:We herein report a highly regioselective reaction for the palladium‐catalyzed oxidative acylation of carbazole derivatives with various aromatic and aliphatic aldehydes as the acyl source. The carbazole derivatives are N‐protected with an easily removable pyridine moiety, which directs the Pd‐catalyzed ortho acylation to occur at the C‐1 and C‐8 positions. The reactions of dibromo‐ and diiodo‐substituted N‐pyridylcarbazole derivatives, however, provide only the 1‐acylated products. This method can be applied to a broad scope of substrates. A reaction mechanism has also been proposed. We have developed a regioselective pyridyl‐directed C–H acylation reaction of carbazoles that employs aldehydes as the acyl source and provides C‐1 and C‐8 diacylated products in good to high yields. Dihalogenated carbazoles, however, afford 1‐acylated products. A key feature of this strategy includes the use of the easily removable pyridyl‐directing group.
ISSN:1434-193X
1099-0690
DOI:10.1002/ejoc.201601322