catalyst-free chemoselective trimerization reaction of readily available isocyanides is described. This domino reaction provides facile access to a wide range of 2-(indol-2-yl)-quinolines and 2-(indol-2-yl)-pyridines in moderate to excellent yields. A “head to head” heterodimerization of two isocyanides is proposed as the key step of this reaction.
The reaction of α-substituted 2-isocyanostyrenes, which could be readily prepared from commercially available 2-aminophenyl ketones or 2-aminobenzonitriles, with sulfur in the presence of a catalytic amount of selenium proceeded smoothly to give the corresponding 2-isothiocyanatestyrenes. The latter spontaneously underwent the electrocyclic reaction to afford 4-substituted quinoline-2(1H)-thiones in one-pot with isolated yields ranging from 37 to 91%.
A domino reaction of o-alkenylaryl isocyanides with elemental sulfur and selenium in pure water was developed for the efficient and green synthesis of quinoline-2-thione and diquinolyl diselenide derivatives. Mechanistical investigation reveals that intramolecular nucleophilic addition of an alkenyl group to the in situ generated isothio/isoselenocyanate accounts for the formation of a quinoline-ring
A visible-light-induced radical cyclization reaction of o-vinylaryl isocyanides and oxime esters to access various 2,4-disubstituted quinolines was disclosed. Oxime esters were employed as acyl radical precursors via the carbon–carbon bond cleavage. It provided an effective way for the synthesis of 2-acyl-4-arlysubstituted quinolines under mild conditions and exhibited good functional group tolerance
The heating of o-isocyanostyrenes (1) in diglyme at reflux temperature for 2 h afforded the corresponding 2,2'-biquinolines (2) via a coupling/electrocyclic reaction in fair-to-good yields.