a) Sulfonation of furan:

The furan sulfones with the SO 3 -Py complex

furan 01 sulfonation

d) Vilsmeier formulation

Furan reacts with dimethylformamide and phosphorus oxytrichloride, followed by basic hydrolysis, to form furan-2-carbaldehyde.
furan vilsmeier
The mechanism is analogous to that described for pyrrole.
e) Mannich reaction
Given the lower reactivity of furan compared to pyrrole and thiophene, the presence of activators on the ring is convenient for this reaction to proceed with good yield.
The Mannich reaction employs methanal, a primary or secondary amine, and hydrochloric acid as reagents. A basic medium stage is used to neutralize.
furan mannich
f) Acetylation
Furan is acetylated in the presence of acid halides or anhydrides with acid catalysis (SnCl 4 )
furan acetylation