Efficient Microwave-Assisted Synthesis of Methyl 4- or 5-Nitro­anthranilate

Abstract

A novel method for the synthesis of anthranilate esters is described. The esterification reaction of nitro-substituted anthranilic acids was carried out under microwave irradiation. A range of solvents and other reaction parameters were investigated to provide the most environmentally friendly reaction conditions. The feasibility of scale-up was demonstrated, allowing a simple and inexpensive production of anthranilate esters.

Synthesis of Trifunctional Thiazole-Fused Anthranilonitrile and Anthranilic Acid Derivatives

“…3 4 5 The last stage of the common strategy involved a regioselective copper(I)-mediated cyclization of ortho -brominated imino-1,2,3-dithiazoles resulting from the reaction of 4,5-dichloro-1,2,3-dithiazolium chloride (commonly known as the Appel salt) 6 with relevant methyl 4- or 5-aminoanthranilates, derived from 4- or 5-nitroanthranilic acids. 7 These compounds were synthesized following a specific multistep sequence: (a) esterification of the starting acid, (b) protection of the amine function, (c) reduction of the nitro group and (d) bromination with N -bromosuccinimide (NBS) to provide o -bromoanilines, before condensation with the Appel salt to give the corresponding ortho -brominated imino-1,2,3-dithiazoles. The difficulties encountered in separating and purifying the ortho -brominated regioisomers were the main drawback during the synthesis of benzothiazoles I – III .…”