I had an idea for a potentially effective way to get from catechol to 4-allylcatechol. I should start by saying that my knowledge of organic chemistry is mostly self-taught, so there are possibly a number of obvious side reactions or problems with the route of which I am unaware.
Basically what I had in mind was bromination of catechol with Br2 and acetic acid. This yields mostly 1,4-dibromo-3,4-dihydroxybenzene as well as some tri-brominated product.
Under the appropriate conditions, allylbromide should react with 2,4-db-3,4-dhb to give 2-allyloxy-1,4-dibromo-3-hydroxybenzene and 3,4-allyloxy-1,4-dibromobenzene. I believe the first product would form preferentially due to some steric hindrance, although I could be wrong. Some multi-phenyl polymers may also form under the same conditions, so overall I am unsure about this step.
If the above is valid, 2-allyloxy-1,4-dibromo-3-hydroxybenzene should be able to undergo Claisen rearrangement to yield 3,6-dibromo-4-allylcatechol. From here there are a few methods of removing the bromine atoms, but they tend to be reduction reactions that would reduce the double bond as well. Okamoto and Oka (attached) have published a method that may work. It's catalyzed by transition metal catalyst and triphenylphosphine.. the latter not being very available that I know of, but the pre-combined catalysts may be. I'm sure there are likely some other ways to do it as well.
Anyway, this is just a rough idea.
Basically what I had in mind was bromination of catechol with Br2 and acetic acid. This yields mostly 1,4-dibromo-3,4-dihydroxybenzene as well as some tri-brominated product.
Under the appropriate conditions, allylbromide should react with 2,4-db-3,4-dhb to give 2-allyloxy-1,4-dibromo-3-hydroxybenzene and 3,4-allyloxy-1,4-dibromobenzene. I believe the first product would form preferentially due to some steric hindrance, although I could be wrong. Some multi-phenyl polymers may also form under the same conditions, so overall I am unsure about this step.
If the above is valid, 2-allyloxy-1,4-dibromo-3-hydroxybenzene should be able to undergo Claisen rearrangement to yield 3,6-dibromo-4-allylcatechol. From here there are a few methods of removing the bromine atoms, but they tend to be reduction reactions that would reduce the double bond as well. Okamoto and Oka (attached) have published a method that may work. It's catalyzed by transition metal catalyst and triphenylphosphine.. the latter not being very available that I know of, but the pre-combined catalysts may be. I'm sure there are likely some other ways to do it as well.
Anyway, this is just a rough idea.
okamoto.pdf
