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29668-44-8

In this step, 3,4-dihydroxybenzaldehyde was used as the starting material to synthesize the intermediate 2,3-dihydro-1,4-benzodioxane-6-carbaldehyde by nucleophilic substitution reaction with 1,2-dibromoethane under alkaline conditions. The base used in this reaction was potassium hydroxide and the phase transfer catalyst was tetrabutylammonium bromide; the molar ratio of the reactants was 3,4-dihydroxybenzaldehyde:1,2-dibromoethane=1:5; the amount of sodium hydroxide was more than five times that of 3,4-dihydroxybenzaldehyde to ensure that the reaction was carried out under strong basic conditions. The reaction temperature was maintained at reflux temperature.