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Chemistry Forums for Students => Organic Chemistry Forum => Organic Chemistry Forum for Graduate Students and Professionals => Topic started by: 23SigmaTropic on March 29, 2016, 01:07:19 AM

Title: Isolating small amounts of high molecular weight silyl ketene acetals
Post by: 23SigmaTropic on March 29, 2016, 01:07:19 AM

Hi Everyone,

I was wondering if it's possible to isolate a silyl ketene acetal, specifically a TES, TBS or TIPS silyl ketene acetal that is also propargylic. I want to isolate it then do a Ireland Claisen/Diels-Alder cascade. I'm worried that the amine produced in the enolate formation will attack my dienophile.  I have found numerous examples in the literature of small MW SKA's, and they are usually isolated by distillation. I'm hoping to isolate a stable SKA derivative of a relatively high boiling ester that I made. My first thought would be some kind of Kughelrohr distillation, but I'm not sure if it would work because I have no  sense of what the bp would be. I'm familiar with the conditions for forming it, but isolating a small amount, say 200 mg, seems like I can't find a similar example in the literature.

Thanks!
 

Title: Re: Isolating small amounts of high molecular weight silyl ketene acetals
Post by: discodermolide on March 29, 2016, 02:10:39 AM

Well chemistry is an experimental science. Try it and see.
Kugelrohr seems a reasonable approach. Which amine did you use? Check its BPt under vacuum.