Reading the very interesting file
https://www.thevespiary.org/rhodium/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
https://www.thevespiary.org/rhodium/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.