INTERACTION OF 2-ALLYLTHIOQUINOLINE-3-CARBALDEHYDE WITH PHENYLSELENIUM TRIBROMIDE

The interaction of 2-allylthioquinoline-3-carbaldehyde with phenylselenium tribromide in solvents of different polarity was investigated in this work . It was found that carrying out the reaction in chloroform leads to the formation of a mixture of bromo- and seleno-induced cyclization products: the major product, 1-bromomethyl-4-formyl-1,2-dihydro[1,3]thiazolo[3,2-a]quinolinium bromide, and the minor product, 1-phenylselenenylmethyl-4-formyl-1,2-dihydro[1,3]thiazolo[3,2-a]quinolinium bromide. This is attributed to the existence of an equilibrium mixture of phenylselenium tribromide, phenylselenenyl bromide, and bromine. In contrast, conducting the reaction in acetonitrile results in the formation of a complex of 1-bromomethyl-4-formyl-1,2-dihydro[1,3]thiazolo[3,2-a]quinolinium bromide with phenylselenenyl bromide. This complex undergoes thermal decomposition upon heating in dichloromethane, yielding the individual 1-bromomethyl-4-formyl-1,2-dihydro[1,3]thiazolo[3,2-a]quinolinium bromide. It was demonstrated that the use of phenylselenium tribromide in solvents such as chloroform and acetonitrile does not promote seleno-induced cyclization in the reaction with the allyl thioether of quinoline-3-carbaldehyde. The content of the selenium-containing aza-annulated quinolinium salt depends on the polarity of the solvent.