Hybrid catalytic effects of K2CO3 on the synthesis of salicylic acid from carboxylation of phenol with CO2
作者:Miaofei Gu、Xingxing Yan、Zhenmin Cheng
DOI:10.1007/s11164-015-2025-2
日期:2016.2
As a base-promoted Kolbe–Schmitt carboxylation reaction, the mechanism of synthesis of salicylic acid derivatives from phenols with CO2 in the industry is still unclear, even up to now. In this paper, synthesis of 3,6-dichloro salicylic acid (3,6-DCSA) from 2,5-dichloro phenoxide and CO2 was investigated in the presence of K2CO3. We show the reaction can proceed by itself, but it goes at a slower rate as well as a lower yield, compared to the case with the addition of K2CO3. However, the yield of 3,6-DCSA is only minorly affected by the size of K2CO3, which cannot be explained from the view of catalytic effect. Therefore, K2CO3 may on one hand act as a catalyst for the activation of CO2 so that the reaction can be accelerated, while on the other hand, it also acts as a co-reactant in deprotonating the phenol formed by the side reaction to phenoxide, which is further converted to salicylate.
作为一种碱促进的Kolbe–Schmitt羧化反应,从苯酚与CO2合成水杨酸衍生物的机制在工业上至今仍不明确。本文研究了在K2CO3存在下,从2,5-二氯苯氧化物及CO2合成3,6-二氯水杨酸(3,6-DCSA)。我们表明,反应可以自行进行,但相比于加入K2CO3的情况,其速率较慢且产率较低。然而,3,6-DCSA的产率仅受到K2CO3大小的轻微影响,这无法从催化效应的角度来解释。因此,K2CO3一方面可能作为催化剂促进CO2的活化,从而加速反应;另一方面,它也作为共同反应物,去质子化由副反应形成的苯酚,使其转化为苯氧根,并进一步转化为水杨酸盐。