Synthesis of 2,4-D ester herbicides - New routes using inorganic solid supports

A clean method for the rapid and solventless preparation of herbicides base d on 2,4-dichlorophenoxyacetic acid (2,4-D esters) is reported. Micro-parti culate inorganic materials such as silica, clays and zeolites are able to a ct as supports for the 2,4-D esterification reactions under mild conditions in the absence of organic solvents. The synthesis takes place with elevate d yield and the conversion rate of the process is strongly enhanced when th e reaction is microwave-assisted. Not only can well-defined supports be use d but soil can also be used for this synthesis, except when iron oxides are present which lead to extensive oxidation under microwave irradiation. The 2,4-D ester remains adsorbed on the solid support as a bioactive product. Therefore the resulting powder is a partially formulated compound that can be directly applied in the field avoiding the use of solvents and with mini mal hazardous and pollutant effects.