Poly(ethylene glycol)-supported 4-alkylthio-substituted aniline - a useful starting material for the soluble polymer-supported synthesis of imines and 1,2,3,4-tetrahydroquinolines

A 4-alkylthio-substituted aniline anchored to a modified poly(ethylene glycol) of Mw = 5000 was selected as a convenient starting material for the liquid-phase synthesis of various imines. Some of these imines were employed in a three-component synthesis of 1,2,3,4-tetrahydroquinolines, carried out in the presence of 2-methylpropanal, different nucleophiles, and catalytic amounts of Yb(OTf)3. Four-component versions of this reaction were also performed. Traceless removal of the heterocycles from the polymer support was accomplished by a reductive desulfurization reaction.