Synthesis of N-Propargyl Pyrrolylamides and Theoretical Study of Pyrrolylimide Reduction by NaBH4

Abstract This study is divided into two parts: experimental and theoretical. In the experimental part, N-propargyl-substituted pyrrolylamide derivatives are synthesized in five steps starting from pyrrole. The main features of this procedure are (i) the synthesis of 2- and 3-nitropyrrole, (ii) the introduction of a propargyl group on the nitrogen atom of the pyrrole, (iii) coupling of various substituents with the alkyne functionality by the Sonogashira reaction, (iv) synthesis of pyrrolylimides by a tin-catalyzed reaction with phthalic anhydride, and, finally, (v) reduction of pyrrolylimides with sodium borohydride (NaBH4) in the presence of water. The theoretical part concerns the reduction mechanism of the pyrrolylimide by NaBH4. The hybrid functional B3LYP in density functional theory is used to determine and discuss the energetics of the compounds.