It is possible to add electrophiles to the 3,4 position of the pyrrole by placing bulky groups on the nitrogen atom, so that the 2,5 positions are prevented. One of the most used groups is triisopropylsilyl.


Stage 1. Strip off the acidic hydrogen, with sodium or potassium bases, to form the pyrrolium ion

Stage 2 . Block the nitrogen couple with triisopropylsilyl chloride.

Stage 3. Carry out the electrophilic substitution, due to steric impediments the electrophile will enter position 3.

Step 4. Remove the silicon group with a fluorine salt.