Dear Tang Xin Ting, I don't think so. There are countless papers available describing the debenzylation though hydrogenation, but virtually no references in which dephenylation is mentioned. I only found one very old paper (see attached) for which I don't have access to the full text. After all, phenyl groups are not really known as protecting groups. The get more specific answers, you should perhaps add a formula drawing of your compounds.

The benzene group in the structure can not be removed by the H2 and Pd/C , However ,the double bonds can be removed when the reaction is carried out under pressure.

Dear Tang Xin Ting , I fully agree with Madhukar Baburao Deshmukh in that hydrogenation with H2 and Pd/C will most likely not remove the phenyl group from your compound. Nevertheless, it would be useful if you could provide a schematic representation of your reaction sequence.

Frank T. Edelmann I have uploaded the schematic reaction. I want to synthesize compound 3 from compound 1. However, I don't have the benzyl 4-hydroxybenzoate. Can you suggest me any other method to get compound 3. I have 4-hydroxybenzoic acid. However, i have to add it dropwise because this compound themselves will undergo esterification too.

Dear Tang Xin Ting, a different idea just came to my mind: Why don't you just buy some benzyl 4-hydroxybenzoate? The compound is available from a large number of commercial sources (see attached list of suppliers). This would certainly facilitate your synthesis.

Instead of benzyl ester go for tert butyl ester. You can get compound 3 using TFA

Dera Tang Xin Ting, I agree with Naganna Thimmaraju in that the tert-butyl ester is also a good alternative. In your diagram, does Bn stand for a benzyl or a phenyl group? In your questions you mentioned benzene, i.e. a phenyl group.

Dear Tang Xin Ting attached please find an article in which the synthesis of closely tert-butyl esters is described. The paper is available open access.

Dear Tang Xin Ting, I also did a literature search (see attached pdf file) for the corresponding carboxylic acid (with a –OMe group in para position). Unfortunately I don't have access to most of the full texts.

Frank T. Edelmann Bn stands for benzyl. but i only have the phenyl one. Thats why I ask can the phenyl be removed by a similar method to remove the phenyl. Thank you Madhukar Baburao Deshmukh Naganna Thimmaraju for the insight.

Dear Tang Xin Ting thanks for the clarification. Benzyl 4-hydroxybenzoate is commercially available from Sigma Aldrich for a reasonable price (see attached).You should ask your supervisor to buy 100 g.

BTW: It is a good practice on RG to recommend answers that have been helpful....

Impossible. Absolutely impossible to remove benzene with hydrogen. I am an university teacher, lecturer in organic chemistry, if in the exam a certain student write me such a thing, I would break him.

Dear T. X. Ting, try to protect carboxylic acid with tert-butyl group as suggested by N. Thimmaraju. After the synthesis of your's target, you may convert it to acid just by Dioxane.HCl/Ether.HCl/Methanol.HCl at 0 oC.

Like many above mentioned, you cannot cleave phenyl ester ("remove benzene") with catalytic hydrogenation. Even more, this cleavage - whether it is phenyl or benzyl group - most likely cannot be done selectively at all, since you already have another phenyl ester in your molecule, formed on the previous step.

Suggested tert-Bu ester instead of either phenyl or benzyl ester is a good advice. Another option could be the use of 4-hydroxybenzaldehyde followed by oxidation of the aldehyde group to carboxylic acid.

I would also make a suggestion to replace DCC/DMAP coupling with acid chloride and Et3N (the acid chloride being prepared with oxalyl chloride/cat. DMF in CH2Cl2 just before the reaction).

Dear Tang Xin Ting what if you just try a basic hydrolysis? Will the end carboxyl group be hydrolyyzed to get your carboxylic acid product?

Frank T. Edelmann I cannot use the basic hydrolysis because my end product will be hydrolysed at the same time.