Synthesis of 3-Organoselenyl Quinolines through the Reduction of Alkynes Mediated by Electrophilic Organoselenium Compounds

A methodology for the synthesis and functionalization of quinolines was developed. This approach involves the cyclization of 2-amino arylalkynyl ketones to 3-(organoselanyl)-4-iodoquinolines through a sequential reaction pathway. The process includes: (i) in situ formation of an electrophilic organoselenyl species, (ii) activation of the alkyne's carbon-carbon bond via a seleniranium ion intermediate, (iii) anti-nucleophilic attack of iodide on the activated triple bond, and (iv) subsequent condensation. The resulting 3-(organoselanyl)-4-iodoquinolines were demonstrated to be versatile substrates, efficiently undergoing Sonogashira cross-coupling to produce 4-alkynyl-quinolines and Ullmann-type reactions to yield the corresponding sulfides. Furthermore, the 4-alkynyl-quinolines were readily converted into selenophene derivatives via halogen-promoted electrophilic cyclization, highlighting the broad applicability of the developed method.