反应详情

More particularly, the present invention relates to a process for the preparation of 3-ethoxy-4-(ethoxycarbonyl)phenyl acetic acid of Formula I, comprising reacting 4-methylsalicylic acid of Formula III, with ethylbromide in a dipolar aprotic solvent at a selected temperature within a range of ambient to 100° C., preferably 30-40° C. during a period of one to several hours. The suitable dipolar aprotic solvent is selected from the group consisting of dimethylsulphoxide, N, N-dimethyl formamide, sulfolane and N-methyl-1-pyrrolidone. The reaction is carried out in the presence of an inorganic base, preferably selected from the group consisting of potassium carbonate and sodium carbonate. The reaction is worked up following the conventional method to afford ethyl 2-ethoxy-4-methylbenzoate of Formula IV in practically quantitative yield. The compound of Formula IV is then reacted with lithium diisopropyl amide (LDA) of Formula VIII,