Palladium catalyzed ortho-C–H-benzoxylation of 2-arylpyridines using iodobenzene dibenzoates
摘要:
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. (C) 2015 Elsevier Ltd. All rights reserved.
o-acyloxylation of 2-phenylpyridine with carboxylic acids using oxygen as the oxidant has been developed. Various acids including aromatic acids, cinnamic acids and aliphatic acids are effective acyloxylation reagents and provide the desired products in moderate to excellent yields. The reaction proceeds well under an oxygen atmosphere, making this method potentially practical.
A palladium-catalyzed direct C–H bond oxidativeacyloxylation of 2-arylpyridines with aromatic carboxylic acids is described. Several 2-arylpyridines derivatives and aromatic carboxylic acids participate in the reaction, providing a series of mono-acyloxylated products in moderate to good yields. Importantly, the reaction can be conducted without using any ligands in a lower temperature.
Highly regioselective copper catalyzed ortho-chlorination of aryl pyridines was achieved with TBHP as oxidant and 1,2-dichloroethane as chlorinating agent for the first time. Switching the oxidant from TBHP to benzoylperoxide under identical reaction conditions effects ortho-oxygenation.
A rhodium-catalyzed ortho-benzoxylation of the sp(2) C-H bond by carboxylic acids Is described. The procedure tolerates carbomethoxy, formyl, bromo, chloro, and nitro groups, providing the benzoxylated products in moderate to good yields. Importantly, no external oxidant was required for the transformation.