[danteOne]

Hi,
I just got my exam back with no answer key. I am trying to figure out how to synthesize this one compound (see picture), but I can't come up with any way to do it. .
This is my (stupid) attempt on the exam.Obviously I added another carbon but didn't notice it at the time so I only got half a point for the problem. I can't think any any way to add a single carbon so that I can form the carboxylic acid.

[orgopete]

Hint, some possibilities, one use a nucleophilic isostere of acetylene anion, two convert protected bromide into a nucleophile, or three, ozone of acetylene.

[danteOne]

what do you mean by

nucleophilic isostere of acetylene anion

?

[orgopete]

Re isostere, ammonia is an isostere of water (though it has more basic properties). I'm trying to help without just giving the answer.

[webassignbuddy]

Omg I know this!

The first thing I would do is use Mg (s) to make a grignard reagent. So you'd draw your same structure and at the end it should look like CH2-MgBr. Then your C can become a nucleophilic C which can attack a formaldehyde, followed by an acid H+ workup.
And THEN you would use your ethylene oxide to protect your ketone. And then you would oxidize the part at the end of the structure with just  Na2Cr2O7/aqueous acid to give you your carboxylic acid at the end. And then you'd have your target molecule.

[discodermolide]

You will have to protect the ketone first before making the Grignard. Quench the Grignard with CO2 to get the acid.

[orgopete]

You will have to protect the ketone first before making the Grignard. Quench the Grignard with CO2 to get the acid.

Yup, that is one way (and I am guessing the textbook route). There are other routes, including additional step(s) from one of the original poster's intermediate.

[danteOne]

Ok thank you. I don't know why I didn't see that. I came up with a few other mechanisms such as using a hindered base (after capping the ketone) to create a double bond then using ozonolosis to create a aldehyde, and then using CrO3 + H2SO4 to make the aldehyde into a ketone. Obviously the Grignard reaction is much better.