Synthesis of 2-carboxy-5,6-ethylenedioxyindole and its 3-, 4-, and 7-halo derivatives

A method for the synthesis of 2-carboxy-5,6-ethylenedioxyindole and its 4- and 7-chloro derivatives from 3,4-ethylenedioxyaniline and, correspondingly, its 2- and 5-chloro derivatives via the Fischer reaction was developed. It was established that in the case of bromination or chlorination under mild conditions 2-carbethoxy-5,6-ethylenedioxyindole forms 3-halo derivatives, while 5,6-ethylenedioxyindole itself forms only 3,7-dihalo derivatives. The closeness in the reactivities of the 3 and 7 ring positions of 5,6-ethylenedioxyindole (as compared with indole) is in agreement with the results of calculations of the quantum-chemical reactivity indexes for electrophilic substitution.Translated from Khimiya Geterotslklicheskikh Soedinenii, No. 9, pp. 1215–1219, September, 1982.