[charnsak]

Hi:

I don't know if I can ask a laboratory question here, but I will ask anyway.

I have been trying to make this amine: tert-octyl tert-butyl amine for 2-3 tries now. And in all attempts, I failed miserably in the third step. The procedure I followed is an Org Syn prep and can be found on Org Syn website. Ref: Org Syn, CV8, 93. Supposedly, this should be a fail-proofed procedure as it was checked that it really works.

I wonder if anyone knows what could have gone wrong in the thrid step or any other of the two steps before it. And can anyone suggest any tricks that will make this reaction works better. I always get low crude yield in the third step and I now suspect the sodium that I used in making sodium naphthalenide. Any help/suggestion would be greatly appreciated.

Todd

[movies]

Was your starting material really dry in the last step?  Note 10 in the org. syn. prep. says that any residual solvent from the previous step makes the yield drop drastically.

[charnsak]

Thank you for your response.

I am pretty sure that my SM was quite dry. There are several things in the third step that I did not know if it was me doing it wrong or it was the reaction that never got mentioned. For example, when I tried to distill the crude product, I could not quite attain the bp reported even though in the proton NMR I know that the product was there.

Also, at some point, a blue/green liquid started to distill from the brown crude mixture. Now I am sure that I did the second step completely that there was no nitroso compound left in the end because I could not see any blue color left. This blue/green liquid that I distilled also turn pink/red upon storage in a fridge. And I have no idea what this was but I think that it is not the remianing nitroso compound. I could not tell anything from the NMR of this stuff except I saw some peaks belonging to the amine.

I am quite desperate as I want to try to make it again for a regioselective enolate formation. But as I failed so many times already, I do not want to fail again and be very frustrated and stuck.

Thanks for any suggestions.    

[movies]

Hmmm...that is odd.  I've never made LOBA before, so I'm not certain of what is happening.

Have you already tried using the other amide bases?  Something like LTMP might be large enough to give good enolate selectivity and the amine is commercially available.

[charnsak]

I have tried all kinds of bulky amine bases. I have tried LDA, LHMDS, LTMP, and LICA. I have also tried to varied temperature. Basically, what I am trying to do is to make a vinyl triflate. The ketone is a methyl ketone with the other side being a CH2 and tertiary C with OR (beta alkoxy group). The best selectivity was actually with LTMP at -115 C, 80:20 at best.  

[movies]

Yeah, LOBA would probably be your best bet if those others haven't worked.  Sorry I can't be of more help.  The org. syn. preps. that I have used have always worked just like they reported.

I assume that you can't buy LOBA either, can you?

[Mitch]

How much experience do you have at chemical synthesis? I just want to eliminate the possibillity it is a technique problem.