Visible-light photocatalytic activation of N-chlorosuccinimide by organic dyes for the chlorination of arenes and heteroarenes
A variety of arenes and heteroarenes are chlorinated in moderate to excellent yields using N-chlorosuccinimide (NCS) under visible-light activated conditions. A screening of known organic dye photocatalysts resulted in the identification of methylene green as the most efficient catalyst to use with NCS. According to mechanistic studies described within, the reaction is speculated to proceed via a single electron oxidation of NCS utilizing methylene green under visible-light photoredox pathway. The photo-oxidation of NCS amplifies the electrophilicity of the chlorine atom of the NCS, thus leading to enhanced reactivity as a chlorinating reagent with aromatic substrates.
Rogers, David A.,Gallegos, Jillian M.,Hopkins, Megan D.,Lignieres, Austin A.,Pitzel, Amy K.,Lamar, Angus A.
Amplification of Trichloroisocyanuric Acid (TCCA) Reactivity for Chlorination of Arenes and Heteroarenes via Catalytic Organic Dye Activation
Heteroarenes and arenes that contain electron-withdrawing groups are chlorinated in good to excellent yields (scalable to gram scale) using trichloroisocyanuric acid (TCCA) and catalytic Brilliant Green (BG). Visible-light activation of BG serves to amplify the electrophilic nature of TCCA, providing a mild alternative approach to acid-promoted chlorination of deactivated (hetero)aromatic substrates. The utility of the TCCA/BG system is demonstrated through comparison to other chlorinating reagents and by the chlorination of pharmaceuticals including caffeine, lidocaine, and phenazone.
Rogers, David A.,Bensalah, Adam T.,Espinosa, Alvaro Tomas,Hoerr, John L.,Refai, Fares H.,Pitzel, Amy K.,Alvarado, Juan J.,Lamar, Angus A.
2-phenylpyrano[2,3-b]pyridines and their use in inhibiting viruses
2-Phenylpyrano[2,3-b]pyridines are described herein. These compounds are active against a variety of viruses. A number of procedures can be used to prepare the compounds of this invention but, at some point, they would all make use of the cyclization of a (phenyl) (pyridyl)propanol or (phenyl) (pyridyl)propenol.
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(2008/06/13)
3,4-Dihydro-2-phenyl-2H-pyranopyridines. Novel Aza Analogs of Flavans
Complementary approaches to the synthesis of the title compounds 1 are described.Metallation of 3,5-dibromo-2-methoxypyridine (5b) by bromine/lithium exchange gave selectively the 3-lithio intermediate 6 which was trapped with substituted cinnamaldehydes
Bargar, T. M.,Wilson, T.,Daniel, J. K.
p. 1583 - 1592
(2007/10/02)
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