PURPOSE: The reaction between at a trithiocyclopropenium salt and a primary amine bearing an electron attractive group through methylene group gives advantageously an N-unsubstituted pyrrole derivative which is useful as intermediate for agricultural chemicals, medicines and various kinds of chemicals.

CONSTITUTION: A trithiocyclopropenium salt of formulaI(R1, R2, R3 are hydrocarbyl or heterocyclic residues which may substituted; X is anion) is reacted with a primary amine of formula II (R4 is electron attractive group) such as benzylamine, chlorobenzylamine, cyanobenzylamine to form a pyrrole derivative of formula III. Further when the resulting compound is treated with hydrogen in the presence of a catalyst such as Raney nickel, -SR1 and -SR2 are eliminated to give a known pyrrole derivative.