Syntheses of quinolines, dihydro- and tetrahydroquinolines via ortho-quinone methide imine intermediate

Abstract

A general process for ortho-specific hydroxyalkylation of secondary anilines via N-alkylanilinochlorophenylboranes has been developed. Pyrolysis of the resulting ortho-aminobenzyl alcohols generated the corresponding ortho-quinone methide imines, which can participate in an electrocyclic reaction to yield 2-substituted-1,2-dihydroquinolines. The resulting dihydroquinolines can be converted readily to a variety of 2-substituted quinolines. Intramolecular trapping of the ortho-quinone methide imines with an olefin via a [2+4] cycloaddition reaction leads to the syntheses of various polycyclic tetrahydroquinolines.