Riemer-Tiemann Reaction

Treating phenol with chloroform (CHCl3) and aqueous NaOH introduces a -CHO group specifically at the ortho position, via a substituted benzal chloride (dichlorocarbene-derived) intermediate that is subsequently hydrolysed by more NaOH; acidic workup then gives salicylaldehyde (2-hydroxybenzaldehyde) as the major product. This is the Riemer-Tiemann reaction, and it is the standard laboratory route to salicylaldehyde. The reactive species is dichlorocarbene (:CCl2), generated in situ from chloroform under the strongly basic conditions, which …