[columbo123]

Hello everybody.
Recently, I am struggling with following reaction (attempt). I have a molecule which contains both, a methyl phenyl ether group and an aliphatic ether chain. For subsequent reactions, I would like to cleave the aryl methyl ether group to obtain a phenol.
So far I tried cleavage with a) high excess AlCl₃ in DCM anh. at RT, and b) 1.1 eq AlCl₃ with 3 eq NaI in MeCN anh. at RT. However, neither pathway worked. Since the aliphatic ether oxygen atoms are more basic, I suspect them to form Lewis acid-base complexes R₂O->AlCl₂ first. That is also, why I haven't tried the classic BBr₃ so far, in fear of it cleaving the aliphatic ether already at RT.

Do you have experience/suggestions with selective ether cleavage reactions? Greetings.

 

[rolnor]

BBr3 will cleave the alkyl ethers faster than the aryl ether. You can use NaSMe in high-boiling solvent, not 100% sure what solvent exactly, collidine? You can find this in Greens protective groups in organic synthesis under protection of phenols, methyl ether.

[columbo123]

Thank you, great suggestion. I will try that right away.

[rolnor]

You need to degass the solvent and  run under N2 or argon, the phenolate product will easily oxidize att high temp.

[BobfromNC]

You can also try MeI in pyridine, but not sure if that will be very selective.   The NaSMe should be pretty good, so that makes sense to try first.

[rolnor]

Do you mean LiI?