[Blackrose]

Hi there, I am new here and I really need help with a reaction mechanism.. I've literally drawn it out like at least 20 times and I'm still doing it wrong, I'm just horrible when it comes to curly arrows and all..

Attached is the reaction itself, if someone can please have a look at it and draw out for me how the reaction happened with the arrows.. I need to explain how it took place and what exactly happened but I can't because I don't understand how it happened!! I'm freaking out here, I really need to have the right mechanism so I can explain it right in my dissertation, any help would be highly appreciated..!

I'm sorry if it sounds as if I want someone to do it for me, I really have tried I just don't know how to get it right and I don't have much time left to play around with it..

[OC pro]

What happens when NaOH comes into play with both starting materials? Are there any acidic protons somewhere?

[Bendzo]

Hello!
I guess this is essentially an Aldol reaction that undergoes ring closure...

[synthnick]

Look at the functional groups, carboxylic acid, aldehyde, methyl ketone.
Also the base can pick up another proton (there are 2 carbonyl group, 1 with α protons) .
Give it a try

[Blackrose]

Ok, if you guys don't mind, I'm going to post the reaction in small steps so you can see what I'm doing..This way you can tell me whether I'm on the right track or not, and I will be able to see where I go wrong as I'm very confused on my own.. Do keep patient with me, I've never been good at this.. =$

Ok so this is the first step in the reaction, if I understood your help right..

[Blackrose]

Step 2..

[Blackrose]

Step 3..

[Blackrose]

I can't believe I spent over 4 hours on this..!! Please ignore my other posts, I think they are wrong..

This is the complete reaction, I hope I've done it right this time, it seems ok but I still have a feeling I missed something out or have some mistakes somewhere, so I would really really appreciate it if someone could look it over for me and give me any feedback.. Thanks for your hints, they really did help a lot!

Ok, I'm off to bed, It seems I'm going to see curly arrows and structures in my dreams, they are dancing in front of my eyes at the moment.. 

[discodermolide]

As far as I can make out that looks OK, except for the ring closure. The carboxylate attacks the C=C in a Michael type of reaction. Thus the electrons move into the C-O bond moving the one of the C=O pairs fully onto the oxygen atom to produce an enolate. So the negative charge you have on that carbon is delocalised into the pi system of the C=O. Pushing the charges back that carbon picks up the proton to give the product. I can draw it if you wish.
But well done anyway.

[Blackrose]

As far as I can make out that looks OK, except for the ring closure. The carboxylate attacks the C=C in a Michael type of reaction. Thus the electrons move into the C-O bond moving the one of the C=O pairs fully onto the oxygen atom to produce an enolate. So the negative charge you have on that carbon is delocalised into the pi system of the C=O. Pushing the charges back that carbon picks up the proton to give the product. I can draw it if you wish.
But well done anyway.

If you can please, I'm not quite understanding what you mean..

[discodermolide]

Here is just the last part I was talking about, compare it with yours.

[Blackrose]

Oh I see, I thought you were talking about the other carbonyl group, but that one stays untouched.. I'll draw the reaction mechanism out again in chemdraw and then place it here.. Now it's complete  .. Thanks a lot..!

[discodermolide]

I think you did very well, I would not even take a mark off in an exam for what you produced.

[orgopete]

Just an opinion, if you treated the lactone with NaOH, it would hydrolyze the lactone. Acidification would recyclize it. I think there had to have been an acidification step to isolate the lactone. I also expect excess base was present to neutralize the carboxylic acid and enolize the ketone.

[Blackrose]

Just an opinion, if you treated the lactone with NaOH, it would hydrolyze the lactone. Acidification would recyclize it. I think there had to have been an acidification step to isolate the lactone. I also expect excess base was present to neutralize the carboxylic acid and enolize the ketone.

I don't understand how to do the above.. But does that mean that my reaction is wrong..?