[littlejoker]

https://picasaweb.google.com/107559539142437649571/Chemistry#6204343049415968994

[Arkcon]

I'd like to welcome you, littlejoker:, to the Chemical Forums but I'd like to ask you to read the Forum Rules{click}.  We like to help you learn to help yourself.  Can you begin to show us your attempt?

[littlejoker]

I´ve been thinking about this for quite a time, but i don´t seem to figure it out. Here´s my idea. I think the hydroxyl group next to the acid group will easily reacts with TsOH to create -OTs, so there may be a subtraction here leading to a double bond. (At first i think the acid group can turn into -COOTs... I just don´t know if this is possible or not...) I also think that the front-hydroxyl group can turn into -OTs too and then we can have an epoxide ring... I just dont know which of this is the beat way for this, and I still dont know how we can combine the given compound with Me2C=O... And neither for the existence of Me2C(OMe)2

[kriggy]

I think you dont combine anything because the product have one oxygen less. The dimethoxypropane works as a water scavenger and TsOH is acidic catalyst IMO. Try working it from there

[orgopete]

I think you dont combine anything because the product have one oxygen less. The dimethoxypropane works as a water scavenger and TsOH is acidic catalyst IMO. Try working it from there

I'd find this to be a difficult reaction to predict the product(s). The ketal may scavenge water, though I don't think that is its purpose here. I think this is a simple exchange reaction with methanol being released.

Hint, since an acid catalyst is present, start with an acid catalyzed reaction.

[littlejoker]

I think 2,2-dimethoxypropane or dimethylketone can combine with the hydroxyl groups at C3,4 of the ring and create another ring

next to the first one.
and -OH next to the acid group turns into OTs and then it is lost to form a double bond. That compound has the formula C10H14O5
Is it possible???

[littlejoker]

It is like


And i just think, if it could be

It looks unstable but just my prediction ==!

[littlejoker]

So sorry , I forgot to add THIS CLUE: (A) can be added with EtOH in the condition of EtOH/EtONa to form a compound which is C₁₂H₂₀O₆ T.T

[orgopete]

That helps. Kriggy's hint applies. I shall assume two moles of ketal are used. The "turns into OTs" suggests this problem is not being solved mechanistically. A mechanism would help in arriving at the intermediate and then final product. What happens when an acid catalyst is present? Hint, Fischer (this will take a little thinking through, or a different intermediate depending on how it actually reacts).

[clarkstill]

And i just think, if it could be

It looks unstable but just my prediction ==!

There are other lactones you could make that would be a little more stable...

[littlejoker]

Dear Clarkstill, do you mean this compound?

[littlejoker]

That helps. Kriggy's hint applies. I shall assume two moles of ketal are used. The "turns into OTs" suggests this problem is not being solved mechanistically. A mechanism would help in arriving at the intermediate and then final product. What happens when an acid catalyst is present? Hint, Fischer (this will take a little thinking through, or a different intermediate depending on how it actually reacts).

I don't really get it... T.T

[clarkstill]

Dear Clarkstill, do you mean this compound?

Yes. If you draw it out in 3D it looks fairly reasonable, I think. Orgopete is hinting at the mechanism of acid catalyzed ester/lactone formation - the Fisher esterification reaction.

[kriggy]

that is the product I had in mind but miscalculated the oxygens and thought that the OH is too far away for lactone formation

[littlejoker]

Yeee, thank you all for helping me :>