[rekhasharma]

I am trying to do the attached synthesis but I am not getting that product, I am using pyridine and triflic anhydride 3 equivalent. I am doing reaction at 0 degree Celcious, but I am getting something else. can somebody explain what is going on in reaction? is it cyclizing somewhere in acidic condition?

[MissPhosgene]

Hello,

I wouldn't expect this reaction to go very well due to the bulk of the groups on the 4-diphenol. What kind of stuff are you getting as product? Do you get a lot of starting material? It seems very doubtful that there would be any type of cyclization going on.

[orgopete]

I would probably try several things with this reaction. Since your hydroquinone is hindered, its reaction may be slowed. I would try any replacing pyridine with triethylamine. Pyridine is a good nucleophile and can form acyl pyridinium salts in acylation reactions, therefore may form sulfonylpyridinium salts here. I don't know the reactivity of that species. Direct reaction of the salt of your hydroquininone with the anhydride or trifluoromethylsulfonyl chloride may work better.

Since you are reacting a hydroquinone, you need to protect it from oxidation or possibly addition of a compatible reductant to the reaction. If any cyclization reactions were to occur, I would expect they might occur via an oxidation mechanism. So avoiding hydroquinone oxidation should prevent any cyclization by-products as well.

[Doc Oc]

I agree that the steric hindrance is the key hurdle in this synthesis.  I think chilling the reaction to 0 also doesn't help with your yield, you will need to wait quite some time, that's likely your issue.

I've worked with triflic anhydride and it goes bad somewhat quickly, even if it's sealed well.  If the bottle is old you may just have triflic acid in there.  If it doesn't smoke when you open the bottle that's a sign that it has potentially gone bad.  Check the NMR of it.

[rekhasharma]

I checked NMR of triflic anhydride. it is good, I have attached the spectra my the product which I am getting. it is not the product which I am expecting. what should I do for this?

[MissPhosgene]

Can you integrate it? How sure are you that it is a single compound?  How do you do the work-up? Did you try IR spectroscopy? 

[rekhasharma]

I have attached the integrated spectra of starting material and the product which I got . It looks like single compound, but I dont know what is that. can u help me in identifying the product.

[MissPhosgene]

Hello, I am not sure enough about what that is to give a definite answer. What was the solvent? Do you have an NMR spectrum of the starting material? Have you tried doing any 13C experiments?