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Topic: Camphorsulfonic acid catalyzed protection of alcohol  (Read 9318 times)

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Offline phth

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Re: Camphorsulfonic acid catalyzed protection of alcohol
« Reply #15 on: September 01, 2015, 12:42:14 AM »
yeah you're right excess water equivalents; HPLC is equilibration conditions.  Needs to be for the separation to work.

Offline clarkstill

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Re: Camphorsulfonic acid catalyzed protection of alcohol
« Reply #16 on: September 01, 2015, 03:06:12 AM »
Is no one going to mention the anomeric effect??

Offline Babcock_Hall

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Re: Camphorsulfonic acid catalyzed protection of alcohol
« Reply #17 on: September 01, 2015, 09:10:36 AM »
The reason for the anomeric effect was controversial the last time I checked in.  However, empirically the methyl pyranosides prefer one diastereomer over the other.  https://books.google.com/books?id=RT_zCAAAQBAJ&pg=PA245&lpg=PA245&dq=methylglucoside+isomers&source=bl&ots=ANQiUdQQyo&sig=wFdqLTL_0JckBzfCRhhLkOC2j-g&hl=en&sa=X&ved=0CCAQ6AEwAGoVChMIw8iS3_PVxwIVAZMNCh2y0g2-#v=onepage&q=methylglucoside%20isomers&f=false

Offline clarkstill

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Re: Camphorsulfonic acid catalyzed protection of alcohol
« Reply #18 on: September 01, 2015, 12:10:28 PM »
There are several schools of thought. For a recent discussion...

http://onlinelibrary.wiley.com/doi/10.1002/anie.201411185/abstract

Offline phth

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Re: Camphorsulfonic acid catalyzed protection of alcohol
« Reply #19 on: September 01, 2015, 06:02:14 PM »
This is exactly why I stated I couldnt come up with the answer;  It needs to be modeled to really tell.  The anomeric effect really is proposed in undergrad textbooks as stuff not interacting with the solvent.  I agree with the authors of the paper that Clarkstill posted; it's all about dipoles and hydrogen bonding/solvation effects.  Another example is β-D-glycopyranose/α-D-glucopyranose is 64/36 in H2O and for mthe same book
Solvents and Solvent Effects in Organic Chemistry, Fourth Edition. Edited by Christian Reichardt and Thomas Welton
Copyright 8 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
ISBN: 978-3-527-32473-6

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