[discodermolide]

10% seems a bit dilute to me.
How much benzylamine are you adding?
Why not use sodium cyanoborohydride?

[Messi]

Yah, I can make it more concentrated. I am using 20mmol of benzylamine.

Does using sodium borohydride or sodium cyanoborohydride make a big difference?

[discodermolide]

Well you can use methanol or THF instead of acetic acid! This means no vast quantities of NaOH solution.
http://en.wikipedia.org/wiki/Sodium_cyanoborohydride
Plus you won't reduce the benzaldehyde!

look at reference 3.

[Messi]

Reference 3 is EXACTLY what I was looking for!!!

Thanks a ton!!!!!!!!

[Messi]

I had found this article as well:

http://www.springerlink.com/content/n8497v0t11852818/fulltext.pdf

[Messi]

Well you can use methanol or THF instead of acetic acid! This means no vast quantities of NaOH solution.
http://en.wikipedia.org/wiki/Sodium_cyanoborohydride
Plus you won't reduce the benzaldehyde!

look at reference 3.

In reference 3, it states to use dimethylamine hydrochloride. Is it a big deal if I just use the amine? In my case I would just use benzylamine.

[Messi]

just react benzylamine with benzyl chloride. add HCl and reflux it at 95 degree Celcius temperature for 1 hour. filtrate the impurities.

Isn't this notoriously messy...

[orgopete]

The other way is to make an amide, alkylate and hydrolyze. I think you could also make the imine and reduce it catalytically. If you have the amine, benzaldehyde and NaBH4, why not try the reductive alkylation with NaBH(OAC)3?

[Messi]

The other way is to make an amide, alkylate and hydrolyze. I think you could also make the imine and reduce it catalytically. If you have the amine, benzaldehyde and NaBH4, why not try the reductive alkylation with NaBH(OAC)3?

Well I wanted to use: http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=CV6P0499

But they used dimethylamine hydrochloride; their amine coupled with HCl. I wasn't sure why this was the case? Is it the same thing as throwing my amine with hydrochloric acid?

[orgopete]

Yes, its been awhile since I read the original paper, but it goes like this. At low pHs, reduction of the ketone is slow, but since the amine forms an iminium salt, it is reduced more rapidly. The cyanoborohydride is stable to lower pHs, so they add acid to maintain the optimum pH for the reaction. Although I don't have a reference to it, I think it is also quite common to use NaBH4 in acetic acid. The first thing that happens is hydrogen is evolved in the formation of NaBH(OAc)3. I believe the same conditions are now present as the cyanoborohydride reduction, imine formation and a faster reduction of it. It has been a while so my memory may not be exactly correct.