1,3,4(2H)‐Isoquinolinetriones: evaluation of amino‐substituted derivatives as redox mediator herbicides

Amino-substituted derivatives of 2-ethyl-1,3,4(2H)-isoquinolinetrione have been prepared with the aim of enhancing their hydrolytic stabilities relative to other isoquinolinetriones, and hence potentially improving their herbicidal effects. 5-Amino-2-ethyl-1,3,4(2H)-isoquinolinetrione has been shown to be 12 and 8 times more stable towards hydrolysis than the isomeric 7- and 8-amino derivatives, respectively, and 120 times more stable than 2-ethyl-1,3,4(2H)-isoquinolinetrione itself. Pulse radiolysis studies have shown 5-amino-2-ethyl-1,3,4(2H)-isoquinolinetrione to have free-radical properties which could enhance the generation of superoxide radicals in plants. The compound is a potent stimulator of the light-dependent consumption of oxygen at photosystem I in isolated chloroplasts and also shows high activity in isolated leaf discs. Evidence is presented which indicates that the rate of foliar uptake is a major factor affecting herbicidal activity for this compound.