2,4-Dichlorobenzoic acid is used as reagent during the synthesis of pyrimido[2?,1?:2,3]thiazolo[4,5-b]quinoxaline derivatives. It is also used as starting reagent during the synthesis of 1-(substituted)-1,4-dihydro-6-nitro-4-oxo-7-(sub-secondary amino)-quinoline-3-carboxylic acids.