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Chemistry Forums for Students => Organic Chemistry Forum => Organic Chemistry Forum for Graduate Students and Professionals => Topic started by: esingh on July 14, 2008, 07:04:01 PM

Title: Schwartz Reagent
Post by: esingh on July 14, 2008, 07:04:01 PM

Hi...
So, I want to use the schwartz reagent to convert a weinreb amide into an aldehyde... has anyone worked with this?... any suggestions for handling it (safety-wise)?

Thanks!

Title: Re: Schwartz Reagent
Post by: macman104 on July 14, 2008, 07:54:43 PM

I've never had any experience with it, but I've attached the MSDS for you.

Title: Re: Schwartz Reagent
Post by: reflux on July 16, 2008, 12:36:39 PM

I haven't used it either.  But as with most organometallics I would keep it under a dry and inert atomsphere.  But is there a reason you can't use DIBAL-H to reduce the Weinreb amide to an aldehyde rather than the much more expensive Zr-reagent?

Title: Re: Schwartz Reagent
Post by: macman104 on July 16, 2008, 06:37:04 PM

I'm not 100% sure about that.  Do you know that DIBAL-H cannot be used?

Also, this article:

http://www.orgsyn.org/orgsyn/prep.asp?prep=cv8p0068

Suggests that LiAlH₄ can be used to reduce the weinreb amide to an aldehyde.

Title: Re: Schwartz Reagent
Post by: esingh on July 16, 2008, 09:16:10 PM

Thanks so much for the posts...
I came across a paper in which the reaction times for forming the aldehyde from the weinreb amide were no longer than 30 min and the yields were also very high (in the 90s)... the use of the Zr-reagent also rarely reduced further to the alcohol.  Here's the paper....
JACS, 2000, 122, p11995-11996.

Title: Re: Schwartz Reagent
Post by: azmanam on July 17, 2008, 11:35:27 AM

DIBAL-H works.  Scifinder comes back with a couple hundred hits for it.

LAH also produces a number of hits, too.

I suppose to an extent it would depend on what other functionality was present in the molecule.

Title: Re: Schwartz Reagent
Post by: mdmpitt on September 24, 2008, 06:19:15 PM

I guess you will end up using DIBAL, but anyway here are some info about Schwartz reagent. I use it very often and I usually prepare it from zirconocene dichloride and LAH. It is good for 1-2 months and needs to be stored in plastic container in dark (I usually wrap the container in Al foil) and cold place. It is susceptible to oxidation and changes color from beige to pink when oxidized.  However, it can be weighed in air without problems, there is no need to keep it in the glovebox.