[rajesh]

Hi,
Can any1 out there help me to break ether linkages selectively when there are 2 ether linkages,I am trying to remove methoxy group from a aromatic system in presence of a pyran ring attached to it by ether linkage.
Waiting for a lots of reply,

fast,
thank you

[reflux]

It would depend on the nature of your ether linkage, but I would try BBr3 at -78 deg C and slowly warm the system if there is no change by TLC.  You could also try a milder protocol which uses BF3-Et2O in a thiol solvent (1,2-ethanedithiol works well) altough this reaction can take days.  Adding a drop of HCl will speed it up a bit.  Both of these methods have worked for me.

Check out Greene's Protective Groups in Organic Synthesis for lots of other methods.

[Miep]

Hi,

Maybe you can try using lithium diphenylphosphide (made of diphenylphosphine and butyllithium).  It's really selective towards methoxy groups...
Don't forget to let us know which one worked!

Miep

[rajesh]

thank u ,
I will try and get back to you if it works if you all have any other ideas let me know

[zq]

I think EtSNa would work.