[owk9688]

Hello!

For the mechanism of EAS, the final step involves deprotonation to restore aromaticity. The driving force to restore aromatcity is so large that even weak bases like water or halides will rapidly accomplish this. My question then is would EAS not be a very clean reaction on arenes that were acid sensitive. For example, TBS/TIPS/TES protected phenols. If you tried to alkylate TBS-phenol with methyl iodide would you deprotect the TBS mid way through the reaction and start to get anisole as a product instead? Or is the generated HI only a strong acid in water (and so if the reaction was kept anhydrous in something like DCM you'd be ok?) ?

[pgk]

1). One way or another, electrophilic aromatic substitution (EAS) involves either a strong mineral acid or a Lewis acid, in order to be accomplished.
2). TBS-phenol will consume the necessary Lewis acid (say AlCl3) and will decrease the yield of the Friedel-Craft alkylation.
3). Acids are stronger in non-aqueous solutions and thus, the generated HI will partially deprotect the phenol, as being a TBS-phenol-Lewis acid complex.
PS: Please, avoid using extreme abbreviations when posting in a website that might have fanatic viewers from more than 150 different countries.

[wildfyr]

I agree that it is essentially impossible to do EAS on a silyl ether protected material. Perhaps the staunchest forms (like dimethylphenyl silyl ether) would not completely fall apart, but it would be poor reaction design.


P.S. Fanatic viewers?