| 摘要 |
The invention is directed to an improved process for the preparation of a compound of formula (I) (see fig. I) wherein R is alkyl, n is 0 to 2, m is 1 to 4 and A is alkyl, interrupted or uninterrupted alkylene, alkanetriyl or pentaerythrityl, by transesterifying the corresponding lower alkyl with a higher alkanol of the formula A-(OH)m in the presence of a tin catalyst; wherein the improvement comprises reacting the tin catalyzed transesterification reaction mass with a carboxylic acid or hydrate thereof neat, in the absence of an aqueous medium, until the tin catalyst forms an insoluble derivative, and then separating the insoluble derivative from the reaction mass by filtration without the assistance of a filtration aid. The invention allows for a convenient method by which to remove the residual tin catalyst from the substituted hydroxyphenylcarboxylic acid ester compounds of formula (I).
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