Metal free synthesis of functionalized 1-aryl isoquinolines via iodine mediated oxidative dehydrogenation and ring opening of lactam in isoindoloisoquinolinones

Abstract

A facile and convenient method for the synthesis of substituted 2-(isoquinolin-1-yl)benzoic acids from isoindoloisoquinolinones in the presence of molecular iodine under sealed tube condition at 100 $$^{\circ }\hbox {C}$$ has been developed. This methodology involves the oxidative dehydrogenation and ring opening of hydroxy lactam/methoxy lactam to furnish the 2-(isoquinolin-1-yl)benzoic acids. Some of these acids are successfully cyclized to furnish the azabenzanthrone derivatives, the potential precursors for the synthesis of menisporphine alkaloids and daurioxoisoaporphines. SYNOPSIS Metal-free synthesis of 1-aryl isoquinolines, which are synthetic precursors for azabenzanthrones or menisporphines, from isoindoloisoquinolinones using iodine under sealed tube conditions is reported. This methodology is successfully utilized to synthesize the 1-azabenzanthrone and analogue of menisporphine, i.e., 5-methoxy-6-hydroxy-1-azabenzanthrone.