bottleneck (Hive Bee)
03-12-03 10:57
No 416206
      Indole + CH2O -> ?  Bookmark   

Reading the very interesting file ../rhodium/pdf /aromatic.aldehyde.synthesis.pdf. there is the description of the condensation of "anilines and phenols" with formaldehyde in "dilute acid or base" to yield the methyl alcohols, a reaction which would appear to be related to the Mannich reaction and chloroalkylation.

I partially dissolved a couple hundred milligrams of of indole in a little formaldehyde (about 5 mL I think). With the addition of a little dilute hydrochloric acid, the solution turned instantly milky white and opaque, and the indole-coloration seemed to vanish.

Having read in ../rhodium/chemistry /benzaldehydes.dmso.html of the conversion of benzyl alcohols to benzaldehydes by reaction with DMSO, I wanted to see if DMSO would also react with any indole-3-methyl alcohol in aqueous solution to yield indole-3-carboxaldehyde, so I added about 10 mL to the reaction-mixture.

However, the next morning, the flask contained a snow white, precipitate with the solvent revealing a reddish coloration, perhaps from some sort of unreacted indole. The precipitate could be filtered, but in a usual act of idiocy I tried washing away discoloration of the with ether, washing away most of the precipitate in the filter paper in the process.

Can anyone offer some suggestions on the likelihood of indole and formaldehyde truly yielding indole-3-methyl alcohol in dilute acid?

What else might the white product consist of?

Any thoughts appreciated.
 
 
 
 
    Lilienthal
(Moderator)
03-12-03 11:58
No 416227
      I think it's just the indole which crashed out  Bookmark   

I think it's just the indole which crashed out of the solution. If you heat that solution in a higher boiling solvent or for a long time you would get the bis-indolyl-methane. It looks like you need strongly basic conditions to get the the hydroxymethylindole.
 
 
 
 
    bottleneck
(Hive Bee)
03-12-03 12:43
No 416241
      Are you sure about the bisindolylmethane ...  Bookmark   


Are you sure about the bisindolylmethane forming in formaldehyde? Doesn't this indicate at least some reactivity of indole towards formaldehyde?

Why do you think it would require a storng base to form the alcohol?

I am not sure if the precipitate could be indole. It was pretty clearly white, different looking from indole. I don't know?