Modeling stages of domino reaction of thiopyrano[4,3-b]indole-3(5H)-thiones and dimethyl acetylenedicarboxylate: a new synthetic route to γ-carbolines with thione group

Abstract

Modeling stages of the cascade reaction of thiopyrano[4,3-b]indole-3(5H)-thiones and dimethyl acetylenedicarboxylate were studied. Alkylation of thiones with alkyl halides or dimethyl sulfate affording to thiopyrano[4,3-b]indole-2-ium salts models the first stage of the process. The attack at the 3-position of the obtained salts by secondary amines can serve as a model for the second stage of the cascade transformation; it gives 3-benzoylindoles with thioamide-group. Reactions of thiopyrano[4,3-b]indole-2-ium salts with primary amines lead to a series of γ-carbolines with thione group. The action of ammonia on these salts causes dealkylation and gives thiopyrano[4,3-b]indole-3(5H)-thiones.

GRAPHICAL ABSTRACT

KEYWORDS:

• Domino reaction
• model reaction
• thiopyrylium salt
• γ-carboline
• indole

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Russian Science Foundation [grant number 23-23-00362], https://rscf.ru/project/23-23-00362.