[zuriel]

Hey all,

See below for the question I'm referring to. I know I'm getting caught mainly because I suspect there is some chemistry involved in transforming 9 to 10 that I have never seen before. I'm wondering if anyone here can drop me a few hints or clarifications to get me on the right track to figuring this one out. Thank you. 

[zuriel]

I have tried to come up with something here. Can someone please check this?

I'm also not sure about the step where I show the reaction of a grignard with an imine. Can anyone shed any light on this? I was discussing it with someone in passing and they suggested it is possible but with some form of activating agent. If anyone with more practical experience has any clarification that would be fantastic.

[orgopete]

You should number the atoms in each step and then check them in the products. Aminal acid stable?

[discodermolide]

In the Grignard addition step the product is not correct, you have missed a carbon out.

[zuriel]

Sorry, the reagent is actually wrong. It should be 2-propenylmagnesium bromide.

[discodermolide]

No not that, in the third structure there is a missing carbon. The amine is not directly attached to the ketal.

[zuriel]

Sorry! I see it now - thanks discodermolide.

Another thing - do you know off of the top of your head if it is possible to react a grignard with an imine. Like I said I have heard activating agents are required. Do you know any such agents?

[discodermolide]

Grignards will react with imines, activation is usually not required.

[orgopete]

… is possible to react a grignard with an imine?

Since this is a paper synthesis, this may be okay, but remember that acidification that makes the magnesium salts soluble also makes the amine into a water soluble ammonium salt.

[zuriel]

OK thanks guys!
I think I have it worked out - I'll post a suggested solution later.