High atom efficient and environment-friendly preparation of herbicides bromoxynil and ioxynil

The use of 3,5-dibromo-4-hydroxybenzonitrile (bromoxynil) I and 3,5-diiodo-4-hydroxybenzonitrile (ioxynil) II are well established as herbicides 1 . Certain esters of bromoxynil, especially the octanoate, have been used extensively as herbicides in the control of broad-leafed weeds, particularly in crop growing areas 2 . Although the esters have been shown to be highly effective, they have been produced only by incurring productivity penalties, which are aggravated by the expensive and cumbersome purifications that have till now been required.