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Author: Subject: Have we been "overcooking" our acetals?
Hazard to Self

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Registered: 3-9-2019
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[*] posted on 10-2-2021 at 10:06
Have we been "overcooking" our acetals?

In orgo 2 they teach that acetal and imines are water sensitive in acid solutions and will be destroyed when they form. I found this paper that uses low concentrations of HCl, with no water removal techniques and gets yields of up to 95% with a typical yield of around 90%. This method is also tolerant of acid sensitive functional groups and leaves alkenes, alkynes, Boc-N, esters, and alpha-beta unsaturated systems intact.
Acetal formation of aldehydes took as little as 20min at RT and aliphatic ketones take about 24 hours at RT. Tested alcohols were MeOH, EtOH, n-PrOH, and ethylene glycol. All had excellent conversions on small scale, and larger gram scale suffers from typical conversion issues.

I don't now if this same procedure will work for imines and enamines. I will hopefully get to test it soonish when the phorone testing is done.
Anyway, I hope this helps someone out because my mind has been blown.

Attachment: Simple acetal formation.pdf (973kB)
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