U.S. Food and Drug Administration-Certified Food Dyes as Organocatalysts in the Visible Light-Promoted Chlorination of Aromatics and Heteroaromatics

David A Rogers; Megan D Hopkins; Nitya Rajagopal; Dhruv Varshney; Haley A Howard; Gabriel LeBlanc; Angus A Lamar

doi:10.1021/acsomega.0c00631

U.S. Food and Drug Administration-Certified Food Dyes as Organocatalysts in the Visible Light-Promoted Chlorination of Aromatics and Heteroaromatics

ACS Omega. 2020 Mar 24;5(13):7693-7704. doi: 10.1021/acsomega.0c00631. eCollection 2020 Apr 7.

Authors

David A Rogers¹, Megan D Hopkins¹, Nitya Rajagopal¹, Dhruv Varshney¹, Haley A Howard¹, Gabriel LeBlanc¹, Angus A Lamar¹

Affiliation

¹ Department of Chemistry and Biochemistry, The University of Tulsa, 800 South Tucker Drive, Tulsa, Oklahoma 74104, United States.

Abstract

Seven FDA-certified food dyes have been investigated as organocatalysts. As a result, Fast Green FCF and Brilliant Blue FCF have been discovered as catalysts for the chlorination of a wide range of arenes and heteroarenes in moderate to excellent yields and high regioselectivity. Mechanistic investigations of the separate systems indicate that different modes of activation are in operation, with Fast Green FCF being a light-promoted photoredox catalyst that is facilitating a one-electron oxidation of N-chlorosuccinimide (NCS) and Brilliant Blue FCF serving as a chlorine-transfer catalyst in its sulfonphthalein form with 1,3-dichloro-5,5-dimethylhydantoin (DCDMH) as stoichiometric chlorine source. Dearomatization of naphthol and indole substrates was observed in some examples using the Brilliant Blue/DCDMH system.