Copper‐Catalyzed Chelation‐Assisted ortho‐Nitration of 2‐Aryls Using Pharmacophoric Benzothiazoles and Benzoxazoles as Directing Groups

Abstract

A copper‐catalyzed chelation‐assisted ortho‐nitration reaction of aryl derivtives has been achieved, using benzazoles as efficient directing groups. The reaction is general and efficient for aryl derivatives with various electronic properties, and also with different pharmacophorically important directing groups, i.e., benzoxazoles, benzothiazoles, and benzimidazoles. The nitro‐group‐containing products have significance as fluorogenic compounds and potential nitroreductase substrates that could be used for the detection of clinically important microorganisms. The nitration reaction proceeds with an inexpensive copper catalyst and a mild, cheap, and environmentally friendly nitro source, Fe(NO3)3·9H2O. This operationally simple and functional‐group‐tolerant protocol for the nitration of 2‐aryl benzazoles proceeds with a high regioselectivity without the exclusion of air or moisture.