Synthesis and theoretical study of pyrrole formiate derivatives through ring contraction of 1,4-dihydropyridines

Crystal structure of ethyl 1-(4-fluorophenyl)-4-phenyl-1H-pyrrole-3-carboxylate, C19H16FNO2

C19H16FNO2, monoclinic, P21/c (no. 14), a = 10.805(7) Å, b = 20.984(13) Å, c = 7.034(4) Å, β = 93.386(13)°, V = 1592.0(17), Z = 4, R gt (F) = 0.0561, wR ref (F 2) = 0.1336, T = 296 K.

Acid-Catalyzed Multicomponent Rearrangements via 2-((Quinoxalin-3(4H)-on-2-yl)(aryl)methylene)malononitriles, Generated In Situ, for Divergent Synthesis of Pyrroles with Different Substitution Patterns

New three-component domino reactions, providing divergent approaches to multifunctionalized pyrroles with different substitution patterns, have been established (47 examples). In this work, a new rearrangement of quinoxalinones with the participation of the in situ-generated 2-en-1-imine moiety of the substituent at C3 makes it possible to construct two new heterocyclic systems, namely, a benzimidazolone and a pyrrole, simultaneously under one-pot reaction conditions. The reaction is easy to perform simply by mixing three common reactants of acetic acid with heating. Secondary amines or primary alcohols as the third component of the reaction, along with quinoxalin-3(4H)-ones and malononitrile, not only initiate the rearrangement but also are responsible for the nature of substituents at position 5 of the pyrrole ring in the newly formed new biheterocyclic system. The reaction proceeds smoothly and can be finished within 7 h, which makes workup convenient to give up to 97% chemical yields.