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Green Chemistry, Cleaner Production(CP) are stratagems which can prevent the industry pollution effecively and realize the sustainabe industry development. Furthermore, the CP is an important means to realize the economy, environment and society benefit.The applications, synthetic routes of hydantoin derivatives and 5-chlorosaclicylic acid were summarized in this paper. The synthetic procedures of 5-chlorosacilicylic acid and 5-bromoethyhydatoin was studied under the guidance of Green Chemistry.The synthesis of 5-bromoethylhydantoin from ethyl cyanoacetate and ethyl malonate respectively was studied. Then an improvmented synthetic process was founed: Ethyl malonate as the start material, via condensation, ammonolysis, hoffmann rearrangement-cyclization and ring-opening to syntheis the product. Total yield was 64.5%. The effects of reacion solvent, reactant ratio, reacion time and catalyst were researched. This improvmented route avoided utilizing bromine and sodium alkoxide which were used in the original process, reduced toxicity and pollution, provided a higher yield and met the demand of Green chemistry. The synthetic route of 2,5-dichlorotoluene to the valuabe downstream product, 5-chlorosaclicylic acid, was chosen: via photochlorination, catalytic hydrolysis and Ullmann reaction to the product. The factors influencing all the reaction, especially, the Ullmann reaction’s catalyst and the Ullmann reaction’s catalyst systerm were studied. Finally, 5-chlorosaclicylic acid was obtained with a yield of 80% from a low economic value product, 2,5-dichlorotoluene.
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