Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: sggwils2 on December 04, 2019, 07:46:55 AM
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Can anyone shed any light on the mechanism for this reaction? BuLi will deprotonate at the tertiary centre first before reaction with PhCHO to give the phenyl alcohol. I am now confused as to what role the tert-BuLi plays as it is a sterically hindered strong base suggesting it would favour a second deprotonation followed by SN2 with the MeI but this yields the incorrect product as it seems the tert-BuLi acts as a nucleophile to give the di-substituted Ph/tert-Bu product before the SiMe3 is lost. Any help appreciated.
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I think steps 1-2 will lead to a Peterson Olefination1, you can probably work from there...
[1] https://www.organic-chemistry.org/namedreactions/peterson-olefination.shtm (https://www.organic-chemistry.org/namedreactions/peterson-olefination.shtm)
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Noted, thank you. Does this seem a logical reaction mechanism?
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That seems like a reasonable proposal given the reagents, but I doubt it'd work in real life - tBuLi is an abysmal nucleophile.
The closest thing I can find in the literature is this: https://www.sciencedirect.com/science/article/pii/S004040390078885X (https://www.sciencedirect.com/science/article/pii/S004040390078885X), but in that case the R-Li nucleophile is tethered so the reaction is intramolecular, and it definitely isn't as hindered as tBuLi.
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tBuLi isn't as bad a nucleophile is you might expect, it apparently reacts via a single electron pathway unlike other alkyllithiums