A new type of plant activator: synthesis of thieno[2,3-d][1,2,3]thiadiazole-6-carboxylic acid derivatives via Hurd–Mori cyclization

Abstract

We present a short and efficient synthesis of the title compounds starting with cheap and readily available methylenebutanedioic acid and thioacetic acid. The optimised sequence allows the large-scale preparation of this new type of plant activator in a few steps. ortho-Lithiation is used for the introduction of substituents into the 5-position. A modified reaction mechanism for the Hurd–Mori reaction is suggested to explain the unexpected aromatisation.