| Indole and its derivatives widely exist in the natural and have importantbiological activities. Indole-sulfonic acid and its analogs are important intermediatesfor preparing dyes and sulfa drugs. The synthese of indole and its derivatives havelong inspired organic chemists. In many synthetic methods, Fischer indole synthesis isone of the most efficient methodologies for the preparation of indoles.Under direction of the Fischer indole synthesis, the different solvents andcatalysts in the reaction between phenylhydrazine-4-sulfonic acid with four differentketo acids were studied, and four indole-sulfonic acids were got. The main conclusionsare as follows:1. Ethyl acetoacetate, ethyl2-methyl-3-oxobutanoate, methyl2-bromoacetate andethyl6-bromohexanoate as starting material and through nucleophilic substitutionreaction, saponification, hydrolysis and decarboxylation, the four keto acids have beenprepared.2. Four indole-sulfonic acids were synthesized respectively with the reactions ofphenyl-hydrazine-4-sulfonic acid and four keto acids under conventional solvent,sulfuric acid and4-toluene sulfonic acid as catalyst.3. Four indole-sulfonic acids were synthesized respectively with the reaction ofphenyl-hydrazine-4-sulfonic acid and four keto acids under the four differentsynthesized ionic liquids as solvents, anhydrous zinc chloride and aluminum chlorideas catalyst.4. Under microwave irradiation, four indole-sulfonic acids were synthesizedrespectively with the reactions of phenylhydrazine-4-sulfonic acid and four keto acidsunder conventional solvent and four different ionic liquids; sulfuric acid, p-toluenesulfonic acid, anhydrous zinc chloride and aluminum chloride as catalyst.5. The synthetic conditions of indole-sulfonic acids under different solvents,catalysts, temperature and microwave irradiation have been optimized, the optimum reaction conditions are [BMIm]BF4as solvent, aluminum chloride as catalyst,600W,80℃,15minutes, the highest yield is76.5%. |
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