The Hive > Methods Discourse
from photo developer to potent hallucinogen
phenethyl_man:
If 1,2-methylenedioxybenzene is activating enough to give good yield, p-dimethoxybenzene would bee too i guess, this is a nice route to 2,5-dimeobenzaldehyde from p-dimethoxybenzene...
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Actually I believe there was a discussion here a while ago where it was stated p-dimethoxybenzene would not work, maybe prevention of the di-substituted product is impossible? This is the exact reason I chose to brominate first; to deactivate the ring somewhat.
did you make the glyoxylic acid yourself? good work phenetylman!
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Nah, it was purchased quite a while ago and was from Acros Organics. However, I don't believe synthesis would be that difficult though; nitric acid oxidation of acetaldehyde to glyoxal and then a further oxidation to glyoxylic acid may be a suitable route. Also procedures from ethylene glycol or from the reduction of oxalic acid are out there.
Antoncho:
I would say the formylation step looks very doubtful to me, considering very different reactivity of 3,4-MD and 1,4-diMeO-2-Br compounds.
phenethyl_man:
I would say the formylation step looks very doubtful to me, considering very different reactivity of 3,4-MD and 1,4-diMeO-2-Br compounds.
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What formylation step? It's a condensation w/the aldehyde functional group of glyoxylic acid to form a subst. mandelic acid and then oxidative decarboxylation to the benzaldehyde.. Do you mean the condensation step to form the acid?
It is a general reaction for aromatics; usually only applied to phenolic compounds. However, I assume the second functional group of glyoxylic acid along with protonation by the acid catalyst makes it a strong enough electrophile to condense w/aromatic ethers as well.
I do agree some ortho-substitution could have taken place, thou I have not the resources to confirm or deny this.. then there's also the possiblility of nitration of the ring during the oxidation step.. so there are definitely disadvantages to this approach.
Saddam_Hussein:
I do agree some ortho-substitution could have taken place, thou I have not the resources to confirm or deny this.. then there's also the possiblility of nitration of the ring during the oxidation step.. so there are definitely disadvantages to this approach.
When brominating 2,5-dimethoxybenzaldehyde, you also obtain a mixture of two isomers. You can remove the 6-bromo isomer by "recrystallization" (dilution). Something similar has been described for nitration. Read up on Rh's page.
I would expect both isomers to be present if the reaction would be possible.
starlight:
"then there's also the possiblility of nitration of the ring during the oxidation step.. so there are definitely disadvantages to this approach".
That does not seem to be a problem if you run the decarboxylation at a low enough temperature and do it in a two phase mixture (aqueous/toluene). The aldehyde goes into the toluene as it is formed. This is speaking from personal experience.
Oh, and use a crystal or two of sodium nitrite to kick start the decarboxylation reaction if you need to. There is no need to use any hydrochloric acid as is suggested in one patent on the Hive.
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