HALOGENOCYCLIZATION OF TERMINAL 2-BUTYNYL(PENTYNYL)THIOQUINOLINE-3-CARBALDEHYDE

Abstract

Polycondensed functional quinoline derivatives exhibit various biological activities. Annulating of nitrogen-containing heterocycles to 3-functionalized quinoline expands the possibilities for discovering bioactive compounds. The electrophilic cyclization of alkylunsaturated thioderivatives of quinoline, under the action of halogen-containing electrophiles, creates prerequisites for the synthesis of polycondensed heterocycles based on quinoline. This study investigates the regio- and stereochemistry of the process of electrophilic intramolecular cyclization of terminal 2-butynyl(pentynyl)thioquinoline-3-carbaldehyde under the influence of molecular and hybrid halogens. For the first time, long-chain alkynyl thioethers of quinoline-3-carbaldehyde were synthesized, which effectively underwent electrophilic heterocyclization reactions under the action of molecular and hybrid halogens. The type of ring fused to quinoline depends on the length of the alkynyl substituent and is independent of the nature of the halogenating agent. It was determined that when bromine acts on alkynyl thioethers of quinoline, bromine-induced heterocyclization occurs, and when iodine, iodine bromide, or iodine chloride act, iodine-induced halogenoheterocyclization occurs. The cyclization process is stereoselective, forming 1-halomethylidene-4-formyl-1,2-dihydro[1,3]thiazino[3,2-a]quinolinium and 1-halomethylidene-6-formyl-1,2,3,4-tetrahydro[1,3]thiazepino-[3,2-a]quinolinium mono- and trihalides with E-configuration.