Stereodivergent Synthesis of Alkenylpyridines via Pd/Cu Catalyzed C-H Alkenylation of Pyridinium Salts with Alkynes
The first Pd/Cu catalyzed selective C2-alkenylation of pyridines with internal alkynes has been developed via the pyridinium salt activation strategy. Importantly, the configuration of the product alkenylpyridines could be tuned by the choice of the proper N-alkyl group of the pyridinium salts, thus allowing for both the Z- and E-alkenylpyridines synthesized with good regio- and stereoselectivity. A plausible mechanism was proposed based on the Hammett study and KIE experiment.
Scope of Successive C-H Functionalizations of the Methyl Group in 3-Picolines: Intramolecular Carbonylation of Arenes to the Metal-Free Synthesis of 4-Azafluorenones
A transition-metal-free, t-BuOOH mediated intramolecular carbonylation of arenes in 2-aryl-3-picolines via oxidative C-H functionalizations of the methyl group has been developed, providing an expedient synthesis of 4-azafluorenones. Distinct from the current literature wherein methylarenes have been used as acylating agents, 2-aryl-3-picolines in this study are transformed into aldehydes, which give 4-azafluorenones upon rapid intramolecular acylation. The study demonstrates the first example of intramolecular carbonylation of arenes utilizing a methyl group as latent carbonyl functionality.
Palladium catalyzed ortho-C-H-benzoxylation of 2-arylpyridines using iodobenzene dibenzoates
A palladium-catalyzed ortho-C-H-benzoxylation of 2-arylpyridines using iodobenzene dibenzoates has been developed. The reaction employed the stable and easily accessible hypervalent iodine reagents as both benzoxylate source and oxidant which made the protocol simple and facile. It showed high regioselectivity and good functional group tolerance, and gave the mono-benzoxylation products in moderate to excellent yields.
A Facile Synthesis of 7-Halo-5H-indenopyridines and -pyridin-5-ones
The 2-aryl-3-methylpyridines 7a-c were obtained in good yield by the addition of the corresponding aryllithium to 2-fluoro-3-methylpyridine.Permanganate oxidation provided the 2-aryl-3-pyridinecarboxylic acids 8a-c which were cyclized to 5H-indenopyridin-5-ones 6a-c in hot polyphosphoric acid.The 5H-indenopyridines 5a-c were readily obtained from the ketones 6a-c by treatment with hydrazine in hot diethylene glycol.
DuPriest, Mark T.,Schmidt, Charles L.,Kuzmich, Daniel,Williams, Stanly B
p. 2021 - 2023
(2007/10/02)
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