[polyrene]

Hello,

I have an alkoxy chain with Tos at the end. I want to make methoxy instead of Tos. Maybe someone have some papers about it?

I am thinking to make this reaction with metallic Na and MeOH. But I still don't know reaction conditions (temperature, equivalents, time and etc). Maybe someone have better suggestions about doing this?

Cheers.

[polyrene]

Oh come on, guys

[sjb]

Seems a bit excessive to me, what else is there in your molecule that may cause chemoselectivity problems?

I'd think you'd be more likely to get something like methyl tosylate and your alcohol back under your conditions?

[polyrene]

Well, acually the synthesis is like that (see the image file).

The tosyl compound is slowly added to a mixture of MeONa (made by dissolving metallic Na in methanol). Reaction mixed overnight at room temperature...but still something is wrong. Too much solid (salts).

I have a question: which reaction part is faster - Tos replacement with MeO or deprotonisation of OH?

[sjb]

Hmmm, I may be looking at this the wrong way, but why can't you methylate the free alcohol (with e.g NaH/MeI or similar, then saponify the tosylate to get the OH at the other end?

S

[macman104]

I would imagine that the substitution would be faster as you might get some anchimeric assistance from the nearby oxygen.

When you said tosyl (and in your image), did you mean that it is an O-Ts group, or just a tosyl connected to the alkyl chain (which I'm not familiar with)?

If it's the first, I'm curious sjb why the O-Ts group won't be kicked out and replaced by the OMe group, as the anion that is kicked out is relatively stabilized and not likely to react further.

How would the methyl tosylate be generated?

I wish I could explain better but I'm on a friends computer and don't really want to "paint" draw what I'm trying to say.

Sorry, hopefully I haven't confused the issue...

[sjb]

Maybe I was getting confused as well.

I read the Ts as tosyl, i.e. 4-toluenesulphfonyl and was picturing something like the first line happening. I read the OP as wanting to methylate in one step, rather than form the alkoxide then alkylate.

If the Ts meant the sulfone, as in the second line I don't think there's an easy way to do a Bayer-Villager style reaction to get a decent leaving group apart from the original alkoxide.

Of course, forming the anion as I suggested may cause problems due to cyclisation, but this may be OK as it would be rather entropically disfavoured IMO.

[polyrene]

Thank you for your help. I found another way how to synthesize that stuff.